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1
Mukhamedov, Farrukh, and Soueidy El Gheteb. "Uniqueness of Quantum Markov Chain Associated with XY-Ising Model on Cayley Tree of Order Two." Open Systems & Information Dynamics 24, no. 02 (June 2017): 1750010. http://dx.doi.org/10.1142/s123016121750010x.
Повний текст джерелаАнотація:
In this paper, we consider backward and forward Quantum Markov Chains (QMC) associated with XY -Ising model on the Cayley tree of order two. We construct finite volume states with boundary conditions, and define QMC as a weak limit of those states which depend on the boundary conditions. We prove that the limit state is a unique QMC associated with such a model, this means the QMC does not depend on the boundary conditions. Moreover, we observe the relation between backward and forward QMC.
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ACCARDI, LUIGI, FARRUKH MUKHAMEDOV, and MANSOOR SABUROV. "ON QUANTUM MARKOV CHAINS ON CAYLEY TREE I: UNIQUENESS OF THE ASSOCIATED CHAIN WITH XY-MODEL ON THE CAYLEY TREE OF ORDER TWO." Infinite Dimensional Analysis, Quantum Probability and Related Topics 14, no. 03 (September 2011): 443–63. http://dx.doi.org/10.1142/s021902571100447x.
Повний текст джерелаАнотація:
In this paper we study forward quantum Markov chains (QMC) defined on Cayley tree. A construction of such QMC is provided, namely we construct states on finite volumes with boundary conditions, and define QMC as a weak limit of those states which depends on the boundary conditions. Using the provided construction, we investigate QMC associated with XY-model on a Cayley tree of order two. We prove uniqueness of QMC associated with such a model, this means the QMC does not depend on the boundary conditions.
3
Honecker, Andreas, Lukas Weber, Philippe Corboz, Frédéric Mila, and Stefan Wessel. "Quantum Monte Carlo simulations of highly frustrated magnets in a cluster basis: The two-dimensional Shastry-Sutherland model." Journal of Physics: Conference Series 2207, no. 1 (March 1, 2022): 012032. http://dx.doi.org/10.1088/1742-6596/2207/1/012032.
Повний текст джерелаАнотація:
Abstract Quantum Monte Carlo (QMC) simulations constitute nowadays one of the most powerful methods to study strongly correlated quantum systems, provided that no “sign problem” arises. However, many systems of interest, including highly frustrated magnets, suffer from an average sign that is close to zero in standard QMC simulations. Nevertheless, a possible sign problem depends on the simulation basis, and here we demonstrate how a suitable choice of cluster basis can be used to eliminate or at least reduce the sign problem in highly frustrated magnets that were so far inaccessible to efficient QMC simulations. We focus in particular on the application of a two-spin (dimer)-based QMC method to the thermodynamics of the spin-1/2 Shastry-Sutherland model for SrCu2(BO3)2.
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Hou, Zenghao, and Joyoung Lee. "Multi-Thread Optimization for the Calibration of Microscopic Traffic Simulation Model." Transportation Research Record: Journal of the Transportation Research Board 2672, no. 20 (September 18, 2018): 98–109. http://dx.doi.org/10.1177/0361198118796395.
Повний текст джерелаАнотація:
This paper proposes an innovative multi-thread stochastic optimization approach for the calibration of microscopic traffic simulation models. Combining Quasi-Monte Carlo (QMC) sampling and the Particle Swarm Optimization (PSO) algorithm, the proposed approach, namely the Quasi-Monte Carlo Particle Swarm (QPS) calibration method, is designed to boost the searching process without prejudice to the calibration accuracy. Given the search space constructed by the combinations of simulation parameters, the QMC sampling technique filters the searching space, followed by the multi-thread optimization through the PSO algorithm. A systematic framework for the implementation of the QPS QMC-initialized PSO method is developed and applied for a case study dealing with a large-scale simulation model covering a 6-mile stretch of Interstate Highway 66 (I-66) in Fairfax, Virginia. The case study results prove that the proposed QPS method outperforms other methods utilizing Genetic Algorithm and Latin Hypercube Sampling in achieving faster convergence to obtain an optimal calibration parameter set.
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Nayak, S. N., P. K. Parida, and P. K. Panda. "Effects of the cosmological constant on compact star in quark-meson coupling model." International Journal of Modern Physics E 24, no. 10 (October 2015): 1550068. http://dx.doi.org/10.1142/s0218301315500688.
Повний текст джерелаАнотація:
We study effect of the cosmological constant on compact star with equation of state provided by quark-meson coupling (QMC) model. In this model, baryons are described as a system of nonoverlapping bags interacting through the scalar and vector mesons. We derive the Tolman–Oppenheimer–Volkoff (TOV) equation taking into account the cosmological constant in static and spherically symmetric metric. Using the equation of state given by QMC model, the mass–radius relationship of the compact star has been computed for various values of the cosmological constant.
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Tronchin, S., H. H. Matevosyan, and A. W. Thomas. "Polarized EMC effect in the QMC model." Physics Letters B 783 (August 2018): 247–52. http://dx.doi.org/10.1016/j.physletb.2018.06.065.
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Antić, S., J. R. Stone, and A. W. Thomas. "Neutron stars from crust to core within the Quark-meson coupling model." EPJ Web of Conferences 232 (2020): 03001. http://dx.doi.org/10.1051/epjconf/202023203001.
Повний текст джерелаАнотація:
Recent years continue to be an exciting time for the neutron star physics, providing many new observations and insights to these natural ‘laboratories’ of cold dense matter. To describe them, there are many models on the market but still none that would reproduce all observed and experimental data. The quark-meson coupling model stands out with its natural inclusion of hyperons as dense matter building blocks, and fewer parameters necessary to obtain the nuclear matter equation of state. The latest advances of the QMC model and its application to the neutron star physics will be presented, within which we build the neutron star’s outer crust from finite nuclei up to the neutron drip line. The appearance of different elements and their position in the crust of a neutron star is explored and compared to the predictions of various models, giving the same quality of the results for the QMC model as for the models when the nucleon structure is not taken into account.
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Hastings, Matthew B. "Obstructions to classically simulating the quantum adiabatic algorithm." Quantum Information and Computation 13, no. 11&12 (November 2013): 1038–76. http://dx.doi.org/10.26421/qic13.11-12-8.
Повний текст джерелаАнотація:
We consider the adiabatic quantum algorithm for systems with ``no sign problem", such as the transverse field Ising model, and analyze the equilibration time for quantum Monte Carlo (QMC) on these systems. We ask: if the spectral gap is only inverse polynomially small, will equilibration methods based on slowly changing the Hamiltonian parameters in the QMC simulation succeed in a polynomial time? We show that this is {\it not} true, by constructing counter-examples. In some examples, the space of configurations where the wavefunction has non-negligible amplitude has a nontrivial fundamental group, causing the space of trajectories in imaginary time to break into disconnected components with only negligible probability outside these components. For the simplest example we give with an abelian fundamental group, QMC does not equilibrate but still solves the optimization problem. More severe effects leading to failure to solve the optimization can occur when the fundamental group is a free group on two generators. Other examples where QMC fails have a {\it trivial} fundamental group, but still use ideas from topology relating group presentations to simplicial complexes. We define gadgets to realize these Hamiltonians as the effective low-energy dynamics of a transverse field Ising model. We present some analytic results on equilibration times which may be of some independent interest in the theory of equilibration of Markov chains. Conversely, we show that a small spectral gap implies slow equilibration at low temperature for some initial conditions and for a natural choice of local QMC updates.
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Zhang, Shuzeng, Canhui Cheng, Xiongbing Li, Yuantian Huang, and Hyunjo Jeong. "Modeling ultrasonic wave fields using a Quasi-Monte Carlo method: Wave transmission through complicated interfaces." Journal of the Acoustical Society of America 152, no. 2 (August 2022): 994–1002. http://dx.doi.org/10.1121/10.0013411.
Повний текст джерелаАнотація:
The sound fields generated by ultrasonic transducers can be modeled using the Quasi-Monte Carlo (QMC) method with a high level of accuracy and efficiency from Zhang [J. Acoust. Soc. Am. 149(1), 7–15 (2021)]. In this work, this method is extended to simulate transmitted wave fields through complicated interfaces. When a wave propagates in two-layer media, the vibrating waves over the interface radiated by the transducer can be treated as the source for generating waves in the second medium, thus, a nested-form Rayleigh integral expression can be used as a model equation for the transmitted wave calculation. When the QMC method is used to solve the nested integral, pseudo-random samples for constructing the transducer and the interface are sampled separately and the transmitted wave fields are obtained using the final sample mean. Numerical examples and results are presented when the wave transmits normally or obliquely through planar or curved interfaces. The results indicate that the high level of accuracy and efficiency remains when the QMC method is used to model the transmitted wave fields. One important advantage is that wave fields can be well simulated using the QMC method when the wave transmits through a complicated interface as long as the interface can be constructed using pseudo-random samples.
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Stone, Jirina R. "Exploring the role of hyperons in high density matter in the Quark-Meson-Coupling model." EPJ Web of Conferences 271 (2022): 09003. http://dx.doi.org/10.1051/epjconf/202227109003.
Повний текст джерелаАнотація:
Microscopic composition and properties of matter at super-saturation densities have been a subject of intense investigations for decades. Experimental and observational data and fundamental laws of physics indicate that heavy strange baryons and mesons are essential components of the matter. The Quark-Meson-Coupling-Model (QMC) is well suited for such a study. The model is based on interaction between quarks in individual baryons instead between the baryons as entities without internal structure. This approach significantly increases transparency and reduces the number of variable parameters of the model, thus offering deeper insight into the physics of high density hadronic matter. In this contribution, we review the effect of hyperons on neutron star (NS) properties, the speed of sound and the symmetry energy, both at zero and finite temperature. The QMC results are contrasted with the outcome of the traditional relativistic mean field DD2Y model. The (lack of) the so-called ‘hyperon puzzle’ in both models is discussed.
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Hu, Zhihui, Xiaoran Wei, Xiaoxu Han, Guang Kou, Haoyu Zhang, Xueyi Liu, and Yefei Bai. "Density Peaks Clustering Based on Feature Reduction and Quasi-Monte Carlo." Scientific Programming 2022 (January 6, 2022): 1–17. http://dx.doi.org/10.1155/2022/8046620.
Повний текст джерелаАнотація:
Density peaks clustering (DPC) is a well-known density-based clustering algorithm that can deal with nonspherical clusters well. However, DPC has high computational complexity and space complexity in calculating local density ρ and distance δ , which makes it suitable only for small-scale data sets. In addition, for clustering high-dimensional data, the performance of DPC still needs to be improved. High-dimensional data not only make the data distribution more complex but also lead to more computational overheads. To address the above issues, we propose an improved density peaks clustering algorithm, which combines feature reduction and data sampling strategy. Specifically, features of the high-dimensional data are automatically extracted by principal component analysis (PCA), auto-encoder (AE), and t-distributed stochastic neighbor embedding (t-SNE). Next, in order to reduce the computational overhead, we propose a novel data sampling method for the low-dimensional feature data. Firstly, the data distribution in the low-dimensional feature space is estimated by the Quasi-Monte Carlo (QMC) sequence with low-discrepancy characteristics. Then, the representative QMC points are selected according to their cell densities. Next, the selected QMC points are used to calculate ρ and δ instead of the original data points. In general, the number of the selected QMC points is much smaller than that of the initial data set. Finally, a two-stage classification strategy based on the QMC points clustering results is proposed to classify the original data set. Compared with current works, our proposed algorithm can reduce the computational complexity from O n 2 to O N n , where N denotes the number of selected QMC points and n is the size of original data set, typically N ≪ n . Experimental results demonstrate that the proposed algorithm can effectively reduce the computational overhead and improve the model performance.
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Huggins, William J., Bryan A. O’Gorman, Nicholas C. Rubin, David R. Reichman, Ryan Babbush, and Joonho Lee. "Unbiasing fermionic quantum Monte Carlo with a quantum computer." Nature 603, no. 7901 (March 16, 2022): 416–20. http://dx.doi.org/10.1038/s41586-021-04351-z.
Повний текст джерелаАнотація:
AbstractInteracting many-electron problems pose some of the greatest computational challenges in science, with essential applications across many fields. The solutions to these problems will offer accurate predictions of chemical reactivity and kinetics, and other properties of quantum systems1–4. Fermionic quantum Monte Carlo (QMC) methods5,6, which use a statistical sampling of the ground state, are among the most powerful approaches to these problems. Controlling the fermionic sign problem with constraints ensures the efficiency of QMC at the expense of potentially significant biases owing to the limited flexibility of classical computation. Here we propose an approach that combines constrained QMC with quantum computation to reduce such biases. We implement our scheme experimentally using up to 16 qubits to unbias constrained QMC calculations performed on chemical systems with as many as 120 orbitals. These experiments represent the largest chemistry simulations performed with the help of quantum computers, while achieving accuracy that is competitive with state-of-the-art classical methods without burdensome error mitigation. Compared with the popular variational quantum eigensolver7,8, our hybrid quantum-classical computational model offers an alternative path towards achieving a practical quantum advantage for the electronic structure problem without demanding exceedingly accurate preparation and measurement of the ground-state wavefunction.
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Mondaini, R., S. Tarat, and R. T. Scalettar. "Quantum critical points and the sign problem." Science 375, no. 6579 (January 28, 2022): 418–24. http://dx.doi.org/10.1126/science.abg9299.
Повний текст джерелаАнотація:
The “sign problem” (SP) is a fundamental limitation to simulations of strongly correlated matter. It is often argued that the SP is not intrinsic to the physics of particular Hamiltonians because its behavior can be influenced by the choice of algorithm. By contrast, we show that the SP in determinant quantum Monte Carlo (QMC) is quantitatively linked to quantum critical behavior. We demonstrate this through simulations of several models with critical properties that are relatively well understood. We propose a reinterpretation of the low average sign for the Hubbard model on the square lattice away from half filling in terms of the onset of pseudogap behavior and exotic superconductivity. Our study charts a path for exploiting the average sign in QMC simulations to understand quantum critical behavior.
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Kazashi, Yoshihito. "Quasi–Monte Carlo integration with product weights for elliptic PDEs with log-normal coefficients." IMA Journal of Numerical Analysis 39, no. 3 (May 23, 2018): 1563–93. http://dx.doi.org/10.1093/imanum/dry028.
Повний текст джерелаАнотація:
Abstract Quasi–Monte Carlo (QMC) integration of output functionals of solutions of the diffusion problem with a log-normal random coefficient is considered. The random coefficient is assumed to be given by an exponential of a Gaussian random field that is represented by a series expansion of some system of functions. Graham et al. (2015, Quasi-Monte Carlo finite element methods for elliptic PDEs with lognormal random coefficients. Numer. Math., 131, 329–368) developed a lattice-based QMC theory for this problem and established a quadrature error decay rate ≈ 1 with respect to the number of quadrature points. The key assumption there was a suitable summability condition on the aforementioned system of functions. As a consequence, product-order-dependent weights were used to construct the lattice rule. In this paper, a different assumption on the system is considered. This assumption, originally considered by Bachmayr et al. (2017c, Sparse polynomial approximation of parametric elliptic PDEs. Part I: affine coefficients. ESAIM Math. Model. Numer. Anal., 51, 321–339) to utilise the locality of support of basis functions in the context of polynomial approximations applied to the same type of the diffusion problem, is shown to work well in the same lattice-based QMC method considered by Graham et al.: the assumption leads us to product weights, which enables the construction of the QMC method with a smaller computational cost than Graham et al. A quadrature error decay rate ≈ 1 is established, and the theory developed here is applied to a wavelet stochastic model. By a characterisation of the Besov smoothness, it is shown that a wide class of path smoothness can be treated with this framework.
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Ribeiro, A. N., and C. A. Macedo. "On the Validity of the Dynamical Mean-Field Approximation for Studying the Two-Dimensional Hubbard Model on a Square Lattice." Advances in Condensed Matter Physics 2010 (2010): 1–5. http://dx.doi.org/10.1155/2010/487381.
Повний текст джерелаАнотація:
The dynamical mean-field approximation (DMFA) becomes exact in the limit of infinite dimensions, and allows results to be obtained in a nonperturbative regime without the limitations normally found with exact diagonalization (ED) and quantum Monte Carlo (QMC) methods. In this paper, we investigate the applicability of the method to lattices with small coordination number in special situations. Specifically we use this approximation to study the two-dimensional (2D) Hubbard model on a square lattice far from half filling. In this situation, we calculate the specific heat and find that when the filling decreases, that is, antiferromagnetic correlations become less important, the agreement between DMFA and QMC results increases. Our results show that the DMFA can be a valuable technique for studying the thermodynamic properties of the Hubbard model also on a square lattice, but within a parameter range in which the antiferromagnetic correlations are not important.
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Sivakumar, Aruna, Chandra R. Bhat, and Giray Ökten. "Simulation Estimation of Mixed Discrete Choice Models with the Use of Randomized Quasi–Monte Carlo Sequences." Transportation Research Record: Journal of the Transportation Research Board 1921, no. 1 (January 2005): 112–22. http://dx.doi.org/10.1177/0361198105192100113.
Повний текст джерелаАнотація:
The overall performance of the quasi–Monte Carlo (QMC) sequences proposed by Halton and Faure, as well as their scrambled versions, are numerically compared against each other and against the Latin hypercube sampling sequence in the context of the simulated likelihood estimation of a mixed multinomial logit model of choice. In addition, the efficiency of the QMC sequences generated with and without scrambling is compared across observations, and the performance of the Box–Muller and inverse normal transform procedures is tested. Numerical experiments were performed in five dimensions with 25, 125, and 625 draws and in 10 dimensions with 100 draws. Results indicate that the Faure sequence consistently outperforms the Halton sequence and that the scrambled versions of the Faure sequence perform best overall.
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Gao, Zhen, and Tao Zhou. "On the Choice of Design Points for Least Square Polynomial Approximations with Application to Uncertainty Quantification." Communications in Computational Physics 16, no. 2 (August 2014): 365–81. http://dx.doi.org/10.4208/cicp.130813.060214a.
Повний текст джерелаАнотація:
AbstractIn this work, we concern with the numerical comparison between different kinds of design points in least square (LS) approach on polynomial spaces. Such a topic is motivated by uncertainty quantification (UQ). Three kinds of design points are considered, which are the Sparse Grid (SG) points, the Monte Carlo (MC) points and the Quasi Monte Carlo (QMC) points. We focus on three aspects during the comparison: (i) the convergence properties; (ii) the stability, i.e. the properties of the resulting condition number of the design matrix; (iii) the robustness when numerical noises are present in function values. Several classical high dimensional functions together with a random ODE model are tested. It is shown numerically that (i) neither the MC sampling nor the QMC sampling introduce the low convergence rate, namely, the approach achieves high order convergence rate for all cases provided that the underlying functions admit certain regularity and enough design points are used; (ii)The use of SG points admits better convergence properties only for very low dimensional problems (say d ≤ 2); (iii)The QMC points, being deterministic, seem to be a good choice for higher dimensional problems not only for better convergence properties but also in the stability point of view.
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Hua, Guo. "In-medium QMC model parameters and quark condensate in nuclear matter." Journal of Physics G: Nuclear and Particle Physics 25, no. 8 (July 26, 1999): 1701–11. http://dx.doi.org/10.1088/0954-3899/25/8/312.
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Otsuka, Yuichi, Kazuhiro Seki, Sandro Sorella, and Seiji Yunoki. "QMC study of the chiral Heisenberg Gross-Neveu universality class." Journal of Physics: Conference Series 2207, no. 1 (March 1, 2022): 012030. http://dx.doi.org/10.1088/1742-6596/2207/1/012030.
Повний текст джерелаАнотація:
Abstract We investigate a quantum criticality of an antiferromagnetic phase transition in the Hubbard model on a square lattice with a d-wave pairing field by large-scale auxiliary-field quantum Monte Carlo simulations. Since the d-wave pairing filed induces Dirac cones in the non-interacting single-particle spectrum, the quantum criticality should correspond to the chiral Heisenberg universality class in terms of the Gross-Neveu theory, which is the same as those expected in the Hubbard model on the honeycomb lattice, despite the unit cells being different (e.g., they contain one and two sites, respectively). We show that both the two phase transitions, expected to occur on the square and on the honeycomb lattices, indeed have the same quantum criticality. We also argue that details of the models, i.e., the way of counting the total number N of fermion components and the anisotropy of the Dirac cones, do not change the critical exponents.
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SAITO, K., K. TSUSHIMA, and A. W. THOMAS. "QUARK AND GLUON CONDENSATES IN THE QUARK–MESON COUPLING MODEL." Modern Physics Letters A 13, no. 10 (March 28, 1998): 769–77. http://dx.doi.org/10.1142/s0217732398000838.
Повний текст джерелаАнотація:
Using the quark–meson coupling (QMC) model, we study the density dependence of the quark and gluon condensates in nuclear matter. We show that the change of the quark condensate is mainly driven by the scalar field in the medium and that the reduction of the quark condensate is suppressed at high density, even in the mean-field approximation. The gluon condensate decreases by 4–6% at nuclear saturation density. We also give a simple relationship between the change of the quark condensate and that of a hadron mass in the medium.
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Bohr, Henrik, Steven A. Moszkowski, Prafulla K. Panda, Constança Providência, and João da Providência. "QMC approach based on the Bogoliubov independent quark model of the nucleon." International Journal of Modern Physics E 25, no. 02 (February 2016): 1650007. http://dx.doi.org/10.1142/s0218301316500075.
Повний текст джерелаАнотація:
The quark–meson coupling (QMC) model due to Guichon is formulated on the basis of the independent quark model of the nucleon proposed by Bogoliubov and is applied to the phenomenological descriptions of symmetric and asymmetric nuclear matter. For symmetric matter, the model predicts, at saturation density, the incompressibility [Formula: see text][Formula: see text]MeV, the quark effective mass [Formula: see text][Formula: see text]MeV and the effective nucleon mass [Formula: see text], where [Formula: see text] is the nucleon mass in vacuum. Neutron star masses above two solar masses are obtained.
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Tchaplianka, M., A. B. Shick, and J. Kolorenč. "Modeling of Co impurity in Cu host using DFT+ED." Journal of Physics: Conference Series 2164, no. 1 (March 1, 2022): 012045. http://dx.doi.org/10.1088/1742-6596/2164/1/012045.
Повний текст джерелаАнотація:
Abstract We investigate the electronic structure of a cobalt atom in a copper host using the density functional theory and the exact diagonalization of an Anderson impurity model. The spectral functions and spin moments at the impurity are calculated and are found to be close the ones calculated by DFT+QMC [1].
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MENG, ZI YANG, HSIANG-HSUAN HUNG, and THOMAS C. LANG. "THE CHARACTERIZATION OF TOPOLOGICAL PROPERTIES IN QUANTUM MONTE CARLO SIMULATIONS OF THE KANE–MELE–HUBBARD MODEL." Modern Physics Letters B 28, no. 01 (December 23, 2013): 1430001. http://dx.doi.org/10.1142/s0217984914300014.
Повний текст джерелаАнотація:
Topological insulators present a bulk gap, but allow for dissipationless spin transport along the edges. These exotic states are characterized by the Z2 topological invariant and are protected by time-reversal symmetry. The Kane–Mele model is one model to realize this topological class in two dimensions, also called the quantum spin Hall state. In this brief review article, we provide a pedagogical introduction to the influence of correlation effects in the quantum spin Hall states, with special focus on the half-filled Kane–Mele–Hubbard model, solved by means of unbiased determinant quantum Monte Carlo (QMC) simulations. We explain the idea of identifying the topological insulator via π-flux insertion, the Z2 invariant and the associated behavior of the zero-frequency Green's function, as well as the spin Chern number in parameter-driven topological phase transitions. The examples considered are two descendants of the Kane–Mele–Hubbard model, the generalized and dimerized Kane–Mele–Hubbard model. From the Z2 index, spin Chern numbers and the Green's function behavior, one can observe that correlation effects induce shifts of the topological phase boundaries. Although the implementation of these topological quantities has been successfully employed in QMC simulations to describe the topological phase transition, we also point out their limitations as well as suggest possible future directions in using numerical methods to characterize topological properties of strongly correlated condensed matter systems.
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Panda, Prafulla K., Constança Providência, Steven A. Moszkowski, Henrik Bohr, and João da Providência. "Hyperonic stars within the Bogoliubov quark meson model for nuclear matter." International Journal of Modern Physics E 28, no. 05 (May 2019): 1950034. http://dx.doi.org/10.1142/s0218301319500344.
Повний текст джерелаАнотація:
We generalize the Bogoliubov quark-meson coupling (QMC) model to also include hyperons. The hyperon-[Formula: see text]-meson couplings are fixed by the model and the hyperon-[Formula: see text]-meson couplings are fitted to the hyperon potentials in symmetric nuclear matter. The present model predicts neutron stars with masses above 2[Formula: see text] and the radius of a 1.4[Formula: see text] star [Formula: see text]14[Formula: see text]km. In the most massive stars, bags overlap at the core of the star, and this may be interpreted as a transition to deconfined quark matter.
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Roberts, W. T. "A Formal Specification of the QMC Message System: The Underlying Abstract Model." Computer Journal 31, no. 4 (August 1, 1988): 313–24. http://dx.doi.org/10.1093/comjnl/31.4.313.
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Guichon, P. A. M., J. R. Stone, and A. W. Thomas. "Quark–Meson-Coupling (QMC) model for finite nuclei, nuclear matter and beyond." Progress in Particle and Nuclear Physics 100 (May 2018): 262–97. http://dx.doi.org/10.1016/j.ppnp.2018.01.008.
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van Osta, Nick, Aurore Lyon, Feddo Kirkels, Tijmen Koopsen, Tim van Loon, Maarten J. Cramer, Arco J. Teske, Tammo Delhaas, Wouter Huberts, and Joost Lumens. "Parameter subset reduction for patient-specific modelling of arrhythmogenic cardiomyopathy-related mutation carriers in the CircAdapt model." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, no. 2173 (May 25, 2020): 20190347. http://dx.doi.org/10.1098/rsta.2019.0347.
Повний текст джерелаАнотація:
Arrhythmogenic cardiomyopathy (AC) is an inherited cardiac disease, clinically characterized by life-threatening ventricular arrhythmias and progressive cardiac dysfunction. Patient-specific computational models could help understand the disease progression and may help in clinical decision-making. We propose an inverse modelling approach using the CircAdapt model to estimate patient-specific regional abnormalities in tissue properties in AC subjects. However, the number of parameters ( n = 110) and their complex interactions make personalized parameter estimation challenging. The goal of this study is to develop a framework for parameter reduction and estimation combining Morris screening, quasi-Monte Carlo (qMC) simulations and particle swarm optimization (PSO). This framework identifies the best subset of tissue properties based on clinical measurements allowing patient-specific identification of right ventricular tissue abnormalities. We applied this framework on 15 AC genotype-positive subjects with varying degrees of myocardial disease. Cohort studies have shown that atypical regional right ventricular (RV) deformation patterns reveal an early-stage AC disease. The CircAdapt model of cardiovascular mechanics and haemodynamics has already demonstrated its ability to capture typical deformation patterns of AC subjects. We, therefore, use clinically measured cardiac deformation patterns to estimate model parameters describing myocardial disease substrates underlying these AC-related RV deformation abnormalities. Morris screening reduced the subset to 48 parameters. qMC and PSO further reduced the subset to a final selection of 16 parameters, including regional tissue contractility, passive stiffness, activation delay and wall reference area. This article is part of the theme issue ‘Uncertainty quantification in cardiac and cardiovascular modelling and simulation’.
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Putikka, W. O., M. U. Luchini, and T. M. Rice. "The Phase Diagram of the Two-Dimensional t-J Model from High Temperature Expansions." International Journal of Modern Physics B 06, no. 05n06 (March 1992): 585. http://dx.doi.org/10.1142/s0217979292000359.
Повний текст джерелаАнотація:
The phase diagram of the 2D t-J model has been investigated using high temperature expansions. Series for the Helmholtz free energy, the inverse compressibility, the chemical potential and the uniform spin susceptibility through tenth order on a square lattice have been calculated using the finite cluster method.1 The series are analytically continued beyond their radius of convergence by Padé and integral approximants. The most accurate extrapolations can be made for the Helmholtz free energy where for J/t≈0.3 and n≈0.9 we can reach T~t/5. We can test the accuracy of the continuation methods by comparing with the 1D results for the boundary of phase separation of Ogata et al.2 In 2D a region of phase separation was found at T=0 for J/t lying above a line extending from J/t=3.8 at zero filling to J/t=1.2 at half filling. No phase separation was found at very small J/t contrary to the earlier suggestion of Emery et al3 which was based on results from exact diagonalisation on 4×4 clusters but in agreement with Quantum Monte Carlo (QMC) calculations on the Hubbard model.4 For very small J/t near half filling where the Nagaoka effect is possible, we find a region of divergent uniform magnetic susceptibility at T=0. However the divergence is very weak when compared with the exponential behaviour expected from a 2D ferromagnet. This might imply a substantially reduced moment which is consistent with the recent QMC estimates of Zhang et al.5
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Tekic, Jasmina, Vidosav Majstorovic, Dejan Markovic, Angelina Nikodijevic, and Dragoslav Stamenkovic. "Quality management in dental health care: Present and future development." Serbian Dental Journal 58, no. 1 (2011): 35–43. http://dx.doi.org/10.2298/sgs1101035t.
Повний текст джерелаАнотація:
The standards ISO 9000 series, brought in 1987, were the driving force for the development and application of quality management (QM) in various areas, including health care. Currently, there are over one million certificates for quality management (QMC), and they were main initiators of quality improvement. In addition to the model for quality management of products/services, other models are also in use. The aim of this study was to present methods and techniques for quality improvement of health services, with special emphasis on dental health care services (DHS), and possibility for enhancement.
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Owerre, Solomon A. "Spin wave theory of spin-1/2 XY model with ring exchange on a triangular lattice." Canadian Journal of Physics 91, no. 7 (July 2013): 542–47. http://dx.doi.org/10.1139/cjp-2012-0462.
Повний текст джерелаАнотація:
We present the linear spin wave theory calculation of the superfluid phase of a hard-core boson J-K model with nearest neighbour exchange J and four-particle ring-exchange K at half filling on the triangular lattice, as well as the phase diagrams of the system at zero and finite temperatures. A similar analysis has been done on a square lattice (Schaffer et al. Phys. Rev. B, 80, 014503 (2009)). We find similar behaviour to that of a square lattice but with different spin wave values of the thermodynamic quantities. We also find that the pure J model (XY model), which has a well-known uniform superfluid phase with an ordered parameter [Formula: see text] at zero temperature is quickly destroyed by the inclusion of negative-K ring-exchange interactions, favouring a state with a (4π/3, 0) ordering wavevector. We further study the behaviour of the finite-temperature Kosterlitz–Thouless phase transition (TKT) in the uniform superfluid phase, by forcing the universal quantum jump condition on the finite-temperature spin wave superfluid density. We find that for K < 0, the phase boundary monotonically decreases to T = 0 at K/J = −4/3, where a phase transition is expected and TKT decreases rapidly, while for positive K, TKT reaches a maximum at some K ≠ 0. It has been shown on a square lattice using quantum Monte Carlo (QMC) simulations that for small K > 0 away from the XY point, the zero-temperature spin stiffness value of the XY model is decreased (Melko and Sandvik. Ann. Phys. 321, 1651 (2006)). Our result seems to agree with this trend found in QMC simulations for two-dimensional systems.
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VAN APPEL, JACQUES, and THOMAS A. MCWALTER. "EFFICIENT LONG-DATED SWAPTION VOLATILITY APPROXIMATION IN THE FORWARD-LIBOR MODEL." International Journal of Theoretical and Applied Finance 21, no. 04 (June 2018): 1850020. http://dx.doi.org/10.1142/s0219024918500206.
Повний текст джерелаАнотація:
We provide efficient swaption volatility approximations for longer maturities and tenors under the lognormal forward-LIBOR model (LFM). In particular, we approximate the swaption volatility with a mean update of the spanning forward rates. Since the joint distribution of the forward rates is not known under a typical pricing measure, we resort to numerical discretization techniques. More specifically, we approximate the mean forward rates with a multi-dimensional weak order 2.0 Itō–Taylor scheme. The higher-order terms allow us to more accurately capture the state dependence in the drift terms and compute conditional expectations with second-order accuracy. We test our approximations for longer maturities and tenors using a quasi-Monte Carlo (QMC) study and find them to be substantially more effective when compared to the existing approximations, particularly for calibration purposes.
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Fettes, Werner, and Ingo Morgenstern. "Limitations of the stochastic diagonalization and the projector QMC in the 2D Hubbard model." Computer Physics Communications 124, no. 2-3 (February 2000): 148–68. http://dx.doi.org/10.1016/s0010-4655(99)00440-3.
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Xie, Zheng, and Doug Edwards. "Computational Performance Optimisation for Statistical Analysis of the Effect of Nano-CMOS Variability on Integrated Circuits." VLSI Design 2013 (July 28, 2013): 1–22. http://dx.doi.org/10.1155/2013/984376.
Повний текст джерелаАнотація:
The intrinsic variability of nanoscale VLSI technology must be taken into account when analyzing circuit designs to predict likely yield. Monte-Carlo- (MC-) and quasi-MC- (QMC-) based statistical techniques do this by analysing many randomised or quasirandomised copies of circuits. The randomisation must model forms of variability that occur in nano-CMOS technology, including “atomistic” effects without intradie correlation and effects with intradie correlation between neighbouring devices. A major problem is the computational cost of carrying out sufficient analyses to produce statistically reliable results. The use of principal components analysis, behavioural modeling, and an implementation of “Statistical Blockade” (SB) is shown to be capable of achieving significant reduction in the computational costs. A computation time reduction of 98.7% was achieved for a commonly used asynchronous circuit element. Replacing MC by QMC analysis can achieve further computation reduction, and this is illustrated for more complex circuits, with the results being compared with those of transistor-level simulations. The “yield prediction” analysis of SRAM arrays is taken as a case study, where the arrays contain up to 1536 transistors modelled using parameters appropriate to 35 nm technology. It is reported that savings of up to 99.85% in computation time were obtained.
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Wu, Mengli, Xianqu Yue, Weibin Chen, Qi Nie, and Yue Zhang. "Accuracy analysis and synthesis of asymmetric parallel mechanism based on Sobol-QMC." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 234, no. 21 (April 22, 2020): 4200–4214. http://dx.doi.org/10.1177/0954406220920702.
Повний текст джерелаАнотація:
Aiming at the aircraft composite skin grinding, a new three degree-of-freedom (DOF) parallel mechanism with asymmetrical structure (TAM) is proposed to replace manual grinding. The TAM is achieved by integrating one of active limbs into the passive limb while keeping the required DOF unchanged, which is divided into two closed-loop chains: telescopic rod and parallelogram. The inverse kinematics models of the two chains are established according to closed-loop vector method. Thus, the actuation and the constraint Jacobian matrix are obtained. Based on the perturbation principle, the error modeling of the TAM is built. Adopting the constraint Jacobian matrix, 15 uncompensated errors are distinguished from the error model. In order to improve the working accuracy of the TAM, accuracy analysis and synthesis are necessary for all the uncompensated errors. The mapping function reflects the influence of uncompensated errors on the pose accuracy. The global sensitivity evaluation indexes are established by mapping function. Since Sobol sequences are superior in uniformity and convergence, the Quasi-Monte Carlo method based on Sobol sequences (Sobol-QMC) is introduced for sensitivity analysis. Taking the minimum manufacturing and installation costs as the optimization target, the objective function of accuracy synthesis is constructed. Ultimately, the reasonable tolerance zone of each uncompensated error is calculated by genetic algorithm. Simulation is performed by Sobol-QMC to verify the rationality of the optimization. The results show the probability is above 97% where most pose errors are in [[Formula: see text], [Formula: see text]] within the workspace. Therefore, accuracy synthesis is correct and practical.
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Yamada, Atsushi. "A study of the magnetic properties in the Hubbard model on the honeycomb lattice by variational cluster approximation." International Journal of Modern Physics B 30, no. 23 (September 15, 2016): 1650158. http://dx.doi.org/10.1142/s0217979216501587.
Повний текст джерелаАнотація:
Magnetic properties of the half-filled Hubbard model on the honeycomb lattice, which is a simple model of graphene, are studied using the variational cluster approximation (VCA). We found that the critical interaction strength of a magnetic transition is slightly lower than that of the nonmagnetic metal-to-insulator transition and the magnetic order parameter is already nonnegligible at the latter transition point. Thus, a semi-metallic state becomes a magnetic insulator as the interaction strength increases, and a spin liquid state characterized by a Mott insulator without spontaneously broken spatial or spin symmetry, or a state very close to that is not realized in this system. Both the magnetic and nonmagnetic metal-to-insulator transitions are of the second-order. Our results agree with recent large scale quantum Monte Carlo (QMC) simulations.
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Kyprioti, Aikaterini P., Ehsan Adeli, Alexandros A. Taflanidis, Joannes J. Westerink, and Hendrik L. Tolman. "Probabilistic Storm Surge Estimation for Landfalling Hurricanes: Advancements in Computational Efficiency Using Quasi-Monte Carlo Techniques." Journal of Marine Science and Engineering 9, no. 12 (November 23, 2021): 1322. http://dx.doi.org/10.3390/jmse9121322.
Повний текст джерелаАнотація:
During landfalling tropical storms, predictions of the expected storm surge are critical for guiding evacuation and emergency response/preparedness decisions, both at regional and national levels. Forecast errors related to storm track, intensity, and size impact these predictions and, thus, should be explicitly accounted for. The Probabilistic tropical storm Surge (P-Surge) model is the established approach from the National Weather Service (NWS) to achieve this objective. Historical forecast errors are utilized to specify probability distribution functions for different storm features, quantifying, ultimately, the uncertainty in the National Hurricane Center advisories. Surge statistics are estimated by using the predictions across a storm ensemble generated by sampling features from the aforementioned probability distribution functions. P-Surge relies, currently, on a full factorial sampling scheme to create this storm ensemble, combining representative values for each of the storm features. This work investigates an alternative formulation that can be viewed as a seamless extension to the current NHC framework, adopting a quasi-Monte Carlo (QMC) sampling implementation with ultimate goal to reduce the computational burden and provide surge predictions with the same degree of statistical reliability, while using a smaller number of sample storms. The definition of forecast errors adopted here directly follows published NWS practices, while different uncertainty levels are considered in the examined case studies, in order to offer a comprehensive validation. This validation, considering different historical storms, clearly demonstrates the advantages QMC can offer.
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Blümer, N., and E. Kalinowski. "Ground state of the frustrated Hubbard model within DMFT: energetics of Mott insulator and metal from ePT and QMC." Physica B: Condensed Matter 359-361 (April 2005): 648–50. http://dx.doi.org/10.1016/j.physb.2005.01.179.
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Wei, Shaoceng, and Richard J. Kryscio. "Semi-Markov models for interval censored transient cognitive states with back transitions and a competing risk." Statistical Methods in Medical Research 25, no. 6 (July 11, 2016): 2909–24. http://dx.doi.org/10.1177/0962280214534412.
Повний текст джерелаАнотація:
Continuous-time multi-state stochastic processes are useful for modeling the flow of subjects from intact cognition to dementia with mild cognitive impairment and global impairment as intervening transient cognitive states and death as a competing risk. Each subject's cognition is assessed periodically resulting in interval censoring for the cognitive states while death without dementia is not interval censored. Since back transitions among the transient states are possible, Markov chains are often applied to this type of panel data. In this manuscript, we apply a semi-Markov process in which we assume that the waiting times are Weibull distributed except for transitions from the baseline state, which are exponentially distributed and in which we assume no additional changes in cognition occur between two assessments. We implement a quasi-Monte Carlo (QMC) method to calculate the higher order integration needed for likelihood estimation. We apply our model to a real dataset, the Nun Study, a cohort of 461 participants.
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Cammell, S. B., D. E. Beever, J. D. Sutton, J. France, the late G. Alderman, and D. J. Humphries. "An examination of energy utilization in lactating dairy cows receiving a total mixed ration based on maize silage." Animal Science 71, no. 3 (December 2000): 585–96. http://dx.doi.org/10.1017/s1357729800055314.
Повний текст джерелаАнотація:
AbstractSix multiparous Holstein-Friesian cows were offered a total mixed ration based on maize silage in a repeated measure design to evaluate the partition of gross energy (GE) during early to mid lactation. Four measurements were made at 6-week intervals with energy and nitrogen balances carried out in open-circuit respiration chambers over 6 days during lactation weeks 6, 12, 18 and 24. The intakes of total diet dry matter (DM) corrected for volatile losses (VCDM), organic matter (OM) and GE declined significantly (P< 0•01) as lactation progressed, although apparent digestibility of these fractions was not altered, resulting in a significant (P< 0•01) decline in digestible nutrient intake at each stage of lactation. Methane and urine energy losses were not significantly affected, resulting in significantly (P< 0·001) higher amounts of digestible energy (DE) partitioned to methane and urine as lactation progressed with associated significant reductions in metabolizable energy (ME) intake (MEI) (P< 0·01) and ME as a proportion of DE (P< 0·001) and GE (q) (P< 0·05). With advancing lactation there was a significant (P< 0·001) increase in the amount of ME partitioned to heat (HP/MEI), but no significant change in the amount partitioned to milk and tissue. Individual values for diet metabolizability (ME/GE) at actual (production) levels (qa) (mean 0·625 MJ/MJ) were corrected to an equivalent value at maintenance (qmc) (mean 0·666 MJ/MJ). The overall ME intakes (MJ/day) were: ad libitum, 246, corrected for level of feeding effect, 263, with a predicted ME requirement according to AFRC (1993) (MER93) of 242. Substitution of the calculated qmc into the predictive equations (AFRC, 1993) resulted in a mean maintenance requirement of 57·6 MJ/day (0·464 MJ/kg M0·75/day) whilst the mean value derived from the linear model describing the experimental data was 82·5 MJ/day (0·664 MJ/kg M0·75/day). The mean efficiencies of utilization of ME for milk production derived from AFRC (1993) and the linear regression model were 0·653 MJ/MJ and 0·625 MJ/MJ respectively.
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Udovsky, A., and O. Fabrichnaya. "About oxide dispersion particles chemical compatibility with areas coherent dissipation/sub-grains of bcc-alloys in Fe - (Cr, V, Mo, W) systems." Journal of Mining and Metallurgy, Section B: Metallurgy 52, no. 2 (2016): 185–88. http://dx.doi.org/10.2298/jmmb151112025u.
Повний текст джерелаАнотація:
A concept of partial magnetic moments (PMM) of the iron atoms located in the first ? four coordination spheres (1?4 CS) for bcc lattice have been introduced based on analysis of results obtained by quantum-mechanical calculations (QMC) for volume dependence of the average magnetic moment ferromagnetic (FM) Fe. The values of these moments have been calculated for pure bcc Fe and bcc - Fe-Cr alloys. This concept has been used to formulate a three sub-lattice model for binary FM alloys of the Fe-M systems (M is an alloying paramagnetic element). Physical reason for sign change dependence of the short-range order and mixing enthalpy obtained by QMCs for Fe-(Cr, V) bcc phases has been found. Using this model it has been predicted that static displacements of Fe - atoms in alloy matrix increase with increasing the of CS number and result in reducing of the area of coherent dissipation (ACD) size with growth of the dimension factor (DF) in the Fe-(Cr, V, Mo, W) systems in agreement with the X-ray experiments. It has been shown theoretically that anisotropy of spin- density in bcc lattice Fe and DF in binary Fe - (Cr, V, Mo, W) systems is main factor for origins of segregations on small angle boundaries of ACD and sub-grains boundaries To prevent the coagulation of both ACD and sub-grains, and to increase the strength of alloys, it is advisable to add oxide dispersion particles into ferrite steel taking into account their chemical compatibility and coherent interfacing with the crystalline lattice of a ferrite matrix. Application of phase diagrams for binary and ternary the Fe-(Y, Zr)-O systems to verify chemical compatibility of oxide dispersion particles with ferrite matrix have been discussed
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Zhao, C., X. Liu, Y. Qian, J. Yoon, Z. Hou, G. Lin, S. McFarlane, et al. "A sensitivity study of radiative fluxes at the top of atmosphere to cloud-microphysics and aerosol parameters in the community atmosphere model CAM5." Atmospheric Chemistry and Physics 13, no. 21 (November 8, 2013): 10969–87. http://dx.doi.org/10.5194/acp-13-10969-2013.
Повний текст джерелаАнотація:
Abstract. In this study, we investigated the sensitivity of net radiative fluxes (FNET) at the top of atmosphere (TOA) to 16 selected uncertain parameters mainly related to the cloud microphysics and aerosol schemes in the Community Atmosphere Model version 5 (CAM5). We adopted a quasi-Monte Carlo (QMC) sampling approach to effectively explore the high-dimensional parameter space. The output response variables (e.g., FNET) are simulated using CAM5 for each parameter set, and then evaluated using the generalized linear model analysis. In response to the perturbations of these 16 parameters, the CAM5-simulated global annual mean FNET ranges from −9.8 to 3.5 W m−2 compared to 1.9 W m−2 with the default parameter values. Variance-based sensitivity analysis is conducted to show the relative contributions of individual parameter perturbations to the global FNET variance. The results indicate that the changes in the global mean FNET are dominated by changes in net cloud forcing (CF) within the parameter ranges being investigated. The threshold size parameter related to auto-conversion of cloud ice to snow is identified as one of the most influential parameters for FNET in CAM5 simulations. The strong heterogeneous geographic distribution of FNET variance shows that parameters have a clear localized effect over regions where they are acting. However, some parameters also have non-local impacts on FNET variance. Although external factors, such as perturbations of anthropogenic and natural emissions, largely affect FNET variance at the regional scale, their impact is weaker than that of model internal parameters in terms of simulating global mean FNET. The interactions among the 16 selected parameters contribute a relatively small portion to the total FNET variance over most regions of the globe. This study helps us better understand the parameter uncertainties in the CAM5 model, and thus provides information for further calibrating uncertain model parameters with the largest sensitivity.
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Lai, Hsin-Hua, and Hsiang-Hsuan Hung. "Short-ranged interaction effects on Z2 topological phase transitions: The perturbative mean-field method." International Journal of Modern Physics B 29, no. 06 (March 2, 2015): 1530005. http://dx.doi.org/10.1142/s0217979215300054.
Повний текст джерелаАнотація:
Time-reversal symmetric topological insulator (TI) is a novel state of matter that a bulk-insulating state carries dissipationless spin transport along the surfaces, embedded by the Z2 topological invariant. In the noninteracting limit, this exotic state has been intensively studied and explored with realistic systems, such as HgTe/(Hg, Cd)Te quantum wells. On the other hand, electronic correlation plays a significant role in many solid-state systems, which further influences topological properties and triggers topological phase transitions. Yet an interacting TI is still an elusive subject and most related analyses rely on the mean-field approximation and numerical simulations. Among the approaches, the mean-field approximation fails to predict the topological phase transition, in particular at intermediate interaction strength without spontaneously breaking symmetry. In this paper, we develop an analytical approach based on a combined perturbative and self-consistent mean-field treatment of interactions that is capable of capturing topological phase transitions beyond either method when used independently. As an illustration of the method, we study the effects of short-ranged interactions on the Z2 TI phase, also known as the quantum spin Hall (QSH) phase, in three generalized versions of the Kane–Mele (KM) model at half-filling on the honeycomb lattice. The results are in excellent agreement with quantum Monte Carlo (QMC) calculations on the same model and cannot be reproduced by either a perturbative treatment or a self-consistent mean-field treatment of the interactions. Our analytical approach helps to clarify how the symmetries of the one-body terms of the Hamiltonian determine whether interactions tend to stabilize or destabilize a topological phase. Moreover, our method should be applicable to a wide class of models where topological transitions due to interactions are in principle possible, but are not correctly predicted by either perturbative or self-consistent treatments.
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Zhao, C., X. Liu, Y. Qian, J. Yoon, Z. Hou, G. Lin, S. McFarlane, et al. "A sensitivity study of radiative fluxes at the top of atmosphere to cloud-microphysics and aerosol parameters in the Community Atmosphere Model CAM5." Atmospheric Chemistry and Physics Discussions 13, no. 5 (May 8, 2013): 12135–76. http://dx.doi.org/10.5194/acpd-13-12135-2013.
Повний текст джерелаАнотація:
Abstract. In this study, we investigated the sensitivity of net radiative fluxes (FNET) at the top of atmosphere (TOA) to 16 selected uncertain parameters mainly related to the cloud microphysics and aerosol schemes in the Community Atmosphere Model version 5 (CAM5). We adopted a quasi-Monte Carlo (QMC) sampling approach to effectively explore the high dimensional parameter space. The output response variables (e.g., FNET) were simulated using CAM5 for each parameter set, and then evaluated using the generalized linear model analysis. In response to the perturbations of these 16 parameters, the CAM5-simulated global annual mean FNET ranges from −9.8 to 3.5 W m−2 compared to the CAM5-simulated FNET of 1.9 W m−2 with the default parameter values. Variance-based sensitivity analysis was conducted to show the relative contributions of individual parameter perturbation to the global FNET variance. The results indicate that the changes in the global mean FNET are dominated by those of net cloud forcing (CF) within the parameter ranges being investigated. The threshold size parameter related to auto-conversion of cloud ice to snow is identified as one of the most influential parameters for FNET in CAM5 simulations. The strong heterogeneous geographic distribution of FNET variance shows parameters have a clear localized effect over regions where they are acting. However, some parameters also have non-local impacts on FNET variance. Although external factors, such as perturbations of anthropogenic and natural emissions, largely affect FNET variance at the regional scale, their impact is weaker than that of model internal parameters in terms of simulating global mean FNET. The interactions among the 16 selected parameters contribute a relatively small portion to the total FNET variance over most regions of the globe. This study helps us better understand the parameter uncertainties in the CAM5 model, and thus provides information for further calibrating uncertain model parameters with the largest sensitivity.
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Tamaki, Ichiro, and Yae Yamada. "Environmental pressure rather than ongoing hybridization is responsible for an altitudinal cline in the morphologies of two oaks." Journal of Plant Ecology 13, no. 4 (May 26, 2020): 413–22. http://dx.doi.org/10.1093/jpe/rtaa028.
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Abstract Aims In a contact zone between related taxa, phenotypic variation can result from genetic and/or environmental gradients. This study aimed to clarify the cause of phenotypic variation in leaf morphology of two Quercus crispula varieties—crispula (QCC) and mongolicoides (QCM)—in their contact zone along an altitudinal gradient. Methods We measured 6 morphological traits of leaves and recorded genotypes of 13 nuclear microsatellite loci for 48 individuals in the contact zone and 24 individuals in each of the reference populations of QCC and QCM. We constructed a model explaining the phenotypic variation (leaf morphology) in relation to environmental (altitude) and genetic (ancestry from the reference population) gradients. Important Findings Both morphological and genetic markers distinguished the two varieties in the reference populations well. We were able to confirm the power of both morphological and genetic markers. Individuals within the contact zone population had intermediate ancestry that was slightly biased to QCM ancestry, and the distribution of their morphologies overlapped with those of the two varieties in the reference populations. The effect of altitude on leaf morphological traits was significant, while that of ancestry was not. Distributions of ancestry and interclass heterozygosity in the contact zone population resembled those in F2 or later generation hybrids. These results indicate that in the contact zone between QCC and QCM, there is no ongoing hybridization, but environmental pressure has created an altitudinal gradient in morphological traits through phenotypic plasticity and/or variation in functional genes.
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Feklin, Vadim G., Marina V. Melnichuk, Svetlana V. Frumina, Anzhela S. Voskovskaya, and Petr V. Nikitin. "Multifactor higher education model taking into account the level of emotional intelligence." Perspectives of Science and Education 58, no. 4 (September 1, 2022): 475–93. http://dx.doi.org/10.32744/pse.2022.4.28.
Повний текст джерелаАнотація:
Introduction and research problem. Determining the criteria for training efficiency or learning outcomes is one of the primary tasks in the analysis of training efficiency. Despite a significant amount of studies on this topic, there are no clear criteria for determining the factors affecting the quality of education. The research purpose is to develop multifactorial higher education models taking into account teachers and students’ emotional intelligence and determine their impact on training efficiency. Materials and methods. More than 800 students from all faculties of the Financial University and more than 100 teachers took part in the study. The dependence of training efficiency on three factors was taken as a basis. Firstly, there are factors related to the educational process (student’s grade-point average (GPA), teacher’s average rating according to the results of the survey “Teacher as Viewed by Students”, etc.). Secondly, socio-cultural factors consisting of indicators of a content-methodological component, a communicative-informational component, a leisure-household component, a creative component, etc. Thirdly, the factors responsible for assessing the emotional intelligence of a student and a teacher. The influence of these factors on students’ performance is statistically analyzed. Two regression models were developed using 375 responses from teachers and students of the Financial University. Results and discussions. Factors that significantly affect the quality of student learning were identified. The resulting indicator is a student’s GPA for the summer examination period of the 2020-2021 academic year (PA_LS) is directly dependent on the following factors: an indicator of decrease in a teacher’s average rating according to the results of the survey “Teacher as Viewed by Students” (IPSGS); an indicator of the content-methodological component (QMC); a student’s GPA on the previous midterm assessment (PA_ZS). PA_LS is inversely related to the emotional intelligence decline indicator (ISEI); the difference between the average value of emotional intelligence of the teachers who taught the students and the emotional intelligence of this student (ROEI); teachers’ average rating based on the results of the survey “Teacher as Viewed by Students” (PGS_2020) and the level of teachers’ emotional intelligence (EI_t_2020). A very high level of significance of the regression equation was obtained, which corresponds to the level of significance α=1.80∙10-75. Moreover, most of the indicated coefficients of the regression equation are significantly different from zero at a significance level of less than 0.05. Conclusions. The study of the influence of teachers and students’ emotional intelligence on training efficiency showed that there is a statistical relationship between them. The developed multifactorial models made it possible to identify the relationship between an increase in students’ knowledge and a teacher’s change, a decrease in his/her emotional intelligence and students’ general emotional intelligence. The degree of influence of the results of the previous examination period on training efficiency was determined, and a slight positive dependence of a grade for current academic performance on the creative component of students’ sociocultural conditions was noted. The use of modeling various components of the educational process on private models using various methods for their development will allow determining the dependences between them and effectively using the results obtained in the management of the educational process. The developed multifactorial higher education models make it possible to assess the existing relationships between teachers and students’ emotional intelligence and various components of the educational process. The obtained modeling results can be directed and effectively used in the academic governance.
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Sun, Xifu, Barry Croke, Stephen Roberts, and Anthony Jakeman. "Investigation of determinism-related issues in the Sobol′ low-discrepancy sequence for producing sound global sensitivity analysis indices." ANZIAM Journal 62 (December 7, 2021): C84—C97. http://dx.doi.org/10.21914/anziamj.v62.16094.
Повний текст джерелаАнотація:
A computationally efficient and robust sampling scheme can support a sensitivity analysis of models to discover their behaviour through Quasi Monte Carlo approximation. This is especially useful for complex models, as often occur in environmental domains when model runtime can be prohibitive. The Sobol' sequence is one of the most used quasi-random low-discrepancy sequences as it can explore the parameter space significantly more evenly than pseudo-random sequences. The built-in determinism of the Sobol' sequence assists in achieving this attractive property. However, the Sobol' sequence tends to deteriorate in the sense that the estimated errors are distributed inconsistently across model parameters as the dimensions of a model increase. By testing multiple Sobol' sequence implementations, it is clear that the deterministic nature of the Sobol' sequence occasionally introduces relatively large errors in sensitivity indices produced by well-known global sensitivity analysis methods, and that the errors do not diminish by averaging through multiple replications. Problematic sensitivity indices may mistakenly guide modellers to make type I and II errors in trying to identify sensitive parameters, and this will potentially impact model reduction attempts based on these sensitivity measurements. This work investigates the cause of the Sobol' sequence's determinism-related issues. References I. A. Antonov and V. M. Saleev. An economic method of computing LPτ-sequences. USSR Comput. Math. Math. Phys. 19.1 (1979), pp. 252–256. doi: 10.1016/0041-5553(79)90085-5 P. Bratley and B. L. Fox. Algorithm 659: Implementing Sobol’s quasirandom sequence generator. ACM Trans. Math. Soft. 14.1 (1988), pp. 88–100. doi: 10.1145/42288.214372 J. Feinberg and H. P. Langtangen. Chaospy: An open source tool for designing methods of uncertainty quantification. J. Comput. Sci. 11 (2015), pp. 46–57. doi: 10.1016/j.jocs.2015.08.008 on p. C90). S. Joe and F. Y. Kuo. Constructing Sobol sequences with better two-dimensional projections. SIAM J. Sci. Comput. 30.5 (2008), pp. 2635–2654. doi: 10.1137/070709359 S. Joe and F. Y. Kuo. Remark on algorithm 659: Implementing Sobol’s quasirandom sequence generator. ACM Trans. Math. Soft. 29.1 (2003), pp. 49–57. doi: 10.1145/641876.641879 W. J. Morokoff and R. E. Caflisch. Quasi-random sequences and their discrepancies. SIAM J. Sci. Comput. 15.6 (1994), pp. 1251–1279. doi: 10.1137/0915077 X. Sun, B. Croke, S. Roberts, and A. Jakeman. Comparing methods of randomizing Sobol’ sequences for improving uncertainty of metrics in variance-based global sensitivity estimation. Reliab. Eng. Sys. Safety 210 (2021), p. 107499. doi: 10.1016/j.ress.2021.107499 S. Tarantola, W. Becker, and D. Zeitz. A comparison of two sampling methods for global sensitivity analysis. Comput. Phys. Com. 183.5 (2012), pp. 1061–1072. doi: 10.1016/j.cpc.2011.12.015 S. Tezuka. Discrepancy between QMC and RQMC, II. Uniform Dist. Theory 6.1 (2011), pp. 57–64. url: https://pcwww.liv.ac.uk/~karpenk/JournalUDT/vol06/no1/5Tezuka11-1.pdf I. M. Sobol′. On the distribution of points in a cube and the approximate evaluation of integrals. USSR Comput. Math. Math. Phys. 7.4 (1967), pp. 86–112. doi: 10.1016/0041-5553(67)90144-9 I. M. Sobol′. Sensitivity estimates for nonlinear mathematical models. Math. Model. Comput. Exp 1.4 (1993), pp. 407–414.
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Li, Zi-Xiang, and Hong Yao. "Sign-Problem-Free Fermionic Quantum Monte Carlo: Developments and Applications." Annual Review of Condensed Matter Physics 10, no. 1 (March 10, 2019): 337–56. http://dx.doi.org/10.1146/annurev-conmatphys-033117-054307.
Повний текст джерелаАнотація:
Reliable simulations of correlated quantum systems, including high-temperature superconductors and frustrated magnets, are increasingly desired nowadays to further our understanding of essential features in such systems. Quantum Monte Carlo (QMC) is a unique numerically exact and intrinsically unbiased method to simulate interacting quantum many-body systems. More importantly, when QMC simulations are free from the notorious fermion sign problem, they can reliably simulate interacting quantum models with large system size and low temperature to reveal low-energy physics such as spontaneously broken symmetries and universal quantum critical behaviors. Here, we concisely review recent progress made in developing new sign-problem-free QMC algorithms, including those employing Majorana representation and those utilizing hot-spot physics. We also discuss applications of these novel sign-problem-free QMC algorithms in simulations of various interesting quantum many-body models. Finally, we discuss possible future directions of designing sign-problem-free QMC methods.
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Gilardoni, S., E. Vignati, F. Cavalli, J. P. Putaud, B. R. Larsen, M. Karl, K. Stenström, J. Genberg, S. Henne, and F. Dentener. "Better constraints on sources of carbonaceous aerosols using a combined <sup>14</sup>C – macro tracer analysis in a European rural background site." Atmospheric Chemistry and Physics Discussions 11, no. 1 (January 24, 2011): 2503–47. http://dx.doi.org/10.5194/acpd-11-2503-2011.
Повний текст джерелаАнотація:
Abstract. The source contributions to carbonaceous PM2.5 aerosol were investigated at a European background site at the edge of the Po Valley, in Northern Italy, during the period January–December 2007. Carbonaceous aerosol was described as the sum of eight source components: primary (1) and secondary (2) biomass burning organic carbon, biomass burning elemental carbon (3), primary (4) and secondary (5) fossil fuel burning organic carbon, fossil fuel burning elemental carbon (6), primary (7) and secondary (8) biogenic organic carbon. The concentration of each component was quantified using a set of macro tracers (organic carbon OC, elemental carbon EC, and levoglucosan), micro tracers (arabitol and mannitol), and 14C measurements. This was the first time that 14C measurements were performed on a long time series of data able to represent the entire annual cycle. This set of 6 tracers, together with assumed uncertainty ranges of the ratios of OC-to-EC, and the fraction of modern carbon in the 8 source categories, provides strong constraints to the source contributions to carbonaceous aerosol. The uncertainty of contributions was assessed with a Quasi-Monte Carlo (QMC) method accounting for the variability of OC and EC emission factors, and the uncertainty of reference fractions of modern carbon. During winter biomass burning composed 50% of the total carbon (TC) concentration, while in summer secondary biogenic OC accounted for 45% of TC. The contribution of primary biogenic aerosol particles was negligible during the entire year. Moreover, aerosol associated with fossil fuel burning represented 26% and 43% of TC in winter and summer, respectively. The comparison of source apportionment results in different urban and rural areas showed that the sampling site was mainly affected by local aerosol sources during winter and regional air masses from the nearby Po Valley in summer. This observation was further confirmed by back-trajectory analysis applying the Potential Source Contribution Function method to identify potential source regions. The contribution of secondary organic aerosol (SOA) to the organic mass (OM) was significant during the entire year. SOA accounted for 23% and 83% of OM during winter and summer, respectively. While the summer SOA was dominated by biogenic sources, winter SOA was mainly due to biomass and fossil fuel burning. This indicates that the oxidation of intermediate volatility organic compounds co-emitted with primary organics is a significant source of SOA, as suggested by recent model results and Aerosol Mass Spectrometer measurements in urban regions. Comparison with previous global model simulations, indicates a strong underestimate of wintertime primary aerosol emissions in this region.
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Gilardoni, S., E. Vignati, F. Cavalli, J. P. Putaud, B. R. Larsen, M. Karl, K. Stenström, J. Genberg, S. Henne, and F. Dentener. "Better constraints on sources of carbonaceous aerosols using a combined <sup>14</sup>C – macro tracer analysis in a European rural background site." Atmospheric Chemistry and Physics 11, no. 12 (June 20, 2011): 5685–700. http://dx.doi.org/10.5194/acp-11-5685-2011.
Повний текст джерелаАнотація:
Abstract. The source contributions to carbonaceous PM2.5 aerosol were investigated at a European background site at the edge of the Po Valley, in Northern Italy, during the period January–December 2007. Carbonaceous aerosol was described as the sum of 8 source components: primary (1) and secondary (2) biomass burning organic carbon, biomass burning elemental carbon (3), primary (4) and secondary (5) fossil organic carbon, fossil fuel burning elemental carbon (6), primary (7) and secondary (8) biogenic organic carbon. The mass concentration of each component was quantified using a set of macro tracers (organic carbon OC, elemental carbon EC, and levoglucosan), micro tracers (arabitol and mannitol), and 14C measurements. This was the first time that 14C measurements covered a full annual cycle with daily resolution. This set of 6 tracers, together with assumed uncertainty ranges of the ratios of OC-to-EC, and the reference fraction of modern carbon in the 8 source categories, provides strong constraints to the source contributions to carbonaceous aerosol. The uncertainty of contributions was assessed with a Quasi-Monte Carlo (QMC) method accounting for the variability of OC and EC emission factors, the uncertainty of reference fractions of modern carbon, and the measurement uncertainty. During winter, biomass burning composed 64 % (±15 %) of the total carbon (TC) concentration, while in summer secondary biogenic OC accounted for 50 % (±16 %) of TC. The contribution of primary biogenic aerosol particles was negligible during the entire year. Moreover, aerosol associated with fossil sources represented 27 % (±16 %) and 41 % (±26 %) of TC in winter and summer, respectively. The contribution of secondary organic aerosol (SOA) to the organic mass (OM) was significant during the entire year. SOA accounted for 30 % (±16 %) and 85 % (±12 %) of OM during winter and summer, respectively. While the summer SOA was dominated by biogenic sources, winter SOA was mainly due to biomass burning and fossil sources. This indicates that the oxidation of semi-volatile and intermediate volatility organic compounds co-emitted with primary organics is a significant source of SOA, as suggested by recent model results and Aerosol Mass Spectrometer measurements. Comparison with previous global model simulations, indicates a strong underestimate of wintertime primary aerosol emissions in this region. The comparison of source apportionment results in different urban and rural areas showed that the sampling site was mainly affected by local aerosol sources during winter and regional air masses from the nearby Po Valley in summer. This observation was further confirmed by back-trajectory analysis applying the Potential Source Contribution Function method to identify potential source regions.
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Gultom, Lipantri Mashur. "Implementasi Beberapa Model Quantum Circuit Pada Penyandian Informasi." Jurnal Fokus Elektroda : Energi Listrik, Telekomunikasi, Komputer, Elektronika dan Kendali) 6, no. 1 (February 28, 2021): 63. http://dx.doi.org/10.33772/jfe.v6i1.16199.
Повний текст джерелаАнотація:
Reversible computing merupakan salah satu karakteristik dari komputasi kuantum. Oleh karena itu komputasi kuantum memiliki kelebihan dibandingkan dengan komputasi biasa. Reversible computing dalam komputasi kuantum dapat dilihat pada quantum circuit yang merupakan rangkaian dari beberapa quantum gate. Pada penelitian ini, quantum circuit dirancang sebagai metode baru dalam penyandian informasi yang disebut dengan Quantum Circuit Chiper (QCC). Ada 4 model QCC yang diusulkan yaitu : QCC dengan pemrosesan karakter per karakter, QCC dengan pemrosesan N karakter, QCC dengan rotation dan QCC dengan kombinasi metode kriptografi lainnya. Hasil pengujian dari beberapa model QCC yang diusulkan bahwa QCC dapat diimplentasikan dengan baik pada proses enkripsi maupun dekripsi.