Articles de revues : « Non-Convex Hamiltonian »

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Ishii, Hitoshi. « The vanishing discount problem for monotone systems of Hamilton-Jacobi equations : a counterexample to the full convergence ». Mathematics in Engineering 5, n^o 4 (2023) : 1–10. http://dx.doi.org/10.3934/mine.2023072.

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<abstract>In recent years there has been intense interest in the vanishing discount problem for Hamilton-Jacobi equations. In the case of the scalar equation, B. Ziliotto has recently given an example of the Hamilton-Jacobi equation having non-convex Hamiltonian in the gradient variable, for which the full convergence of the solutions does not hold as the discount factor tends to zero. We give here an explicit example of nonlinear monotone systems of Hamilton-Jacobi equations having convex Hamiltonians in the gradient variable, for which the full convergence of the solutions fails as the discount factor goes to zero.</abstract>

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Hayat, Sakander, Muhammad Yasir Hayat Malik, Ali Ahmad, Suliman Khan, Faisal Yousafzai et Roslan Hasni. « On Hamilton-Connectivity and Detour Index of Certain Families of Convex Polytopes ». Mathematical Problems in Engineering 2021 (17 juillet 2021) : 1–18. http://dx.doi.org/10.1155/2021/5553216.

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A convex polytope is the convex hull of a finite set of points in the Euclidean space ℝ n . By preserving the adjacency-incidence relation between vertices of a polytope, its structural graph is constructed. A graph is called Hamilton-connected if there exists at least one Hamiltonian path between any of its two vertices. The detour index is defined to be the sum of the lengths of longest distances, i.e., detours between vertices in a graph. Hamiltonian and Hamilton-connected graphs have diverse applications in computer science and electrical engineering, whereas the detour index has important applications in chemistry. Checking whether a graph is Hamilton-connected and computing the detour index of an arbitrary graph are both NP-complete problems. In this paper, we study these problems simultaneously for certain families of convex polytopes. We construct two infinite families of Hamilton-connected convex polytopes. Hamilton-connectivity is shown by constructing Hamiltonian paths between any pair of vertices. We then use the Hamilton-connectivity to compute the detour index of these families. A family of non-Hamilton-connected convex polytopes has also been constructed to show that not all convex polytope families are Hamilton-connected.

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Pittman, S. M., E. Tannenbaum et E. J. Heller. « Dynamical tunneling versus fast diffusion for a non-convex Hamiltonian ». Journal of Chemical Physics 145, n^o 5 (7 août 2016) : 054303. http://dx.doi.org/10.1063/1.4960134.

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Hayat, Sakander, Asad Khan, Suliman Khan et Jia-Bao Liu. « Hamilton Connectivity of Convex Polytopes with Applications to Their Detour Index ». Complexity 2021 (23 janvier 2021) : 1–23. http://dx.doi.org/10.1155/2021/6684784.

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A connected graph is called Hamilton-connected if there exists a Hamiltonian path between any pair of its vertices. Determining whether a graph is Hamilton-connected is an NP-complete problem. Hamiltonian and Hamilton-connected graphs have diverse applications in computer science and electrical engineering. The detour index of a graph is defined to be the sum of lengths of detours between all the unordered pairs of vertices. The detour index has diverse applications in chemistry. Computing the detour index for a graph is also an NP-complete problem. In this paper, we study the Hamilton-connectivity of convex polytopes. We construct three infinite families of convex polytopes and show that they are Hamilton-connected. An infinite family of non-Hamilton-connected convex polytopes is also constructed, which, in turn, shows that not all convex polytopes are Hamilton-connected. By using Hamilton connectivity of these families of graphs, we compute exact analytical formulas of their detour index.

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CONTRERAS, GONZALO, et RENATO ITURRIAGA. « Convex Hamiltonians without conjugate points ». Ergodic Theory and Dynamical Systems 19, n^o 4 (août 1999) : 901–52. http://dx.doi.org/10.1017/s014338579913387x.

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We construct the Green bundles for an energy level without conjugate points of a convex Hamiltonian. In this case we give a formula for the metric entropy of the Liouville measure and prove that the exponential map is a local diffeomorphism. We prove that the Hamiltonian flow is Anosov if and only if the Green bundles are transversal. Using the Clebsch transformation of the index form we prove that if the unique minimizing measure of a generic Lagrangian is supported on a periodic orbit, then it is a hyperbolic periodic orbit.We also show some examples of differences with the behaviour of a geodesic flow without conjugate points, namely: (non-contact) flows and periodic orbits without invariant transversal bundles, segments without conjugate points but with crossing solutions and non-surjective exponential maps.

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Zhou, Min, et Binggui Zhong. « Regions of applicability of Aubry-Mather Theory for non-convex Hamiltonian ». Chinese Annals of Mathematics, Series B 32, n^o 4 (juillet 2011) : 605–14. http://dx.doi.org/10.1007/s11401-011-0654-3.

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You, Bo, Zhi Li, Liang Ding, Haibo Gao et Jiazhong Xu. « A new optimization-driven path planning method with probabilistic completeness for wheeled mobile robots ». Measurement and Control 52, n^o 5-6 (15 avril 2019) : 317–25. http://dx.doi.org/10.1177/0020294019836127.

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Wheeled mobile robots are widely utilized for environment-exploring tasks both on earth and in space. As a basis for global path planning tasks for wheeled mobile robots, in this study we propose a method for establishing an energy-based cost map. Then, we utilize an improved dual covariant Hamiltonian optimization for motion planning method, to perform point-to-region path planning in energy-based maps. The method is capable of efficiently handling high-dimensional path planning tasks with non-convex cost functions through applying a robust active set algorithm, that is, non-monotone gradient projection algorithm. To solve the problem that the path planning process is locked in weak minima or non-convergence, we propose a randomized variant of the improved dual covariant Hamiltonian optimization for motion planning based on simulated annealing and Hamiltonian Monte Carlo methods. The results of simulations demonstrate that the final paths generated can be time efficient, energy efficient and smooth. And the probabilistic completeness of the method is guaranteed.

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Cordaro, Giuseppe. « Existence and location of periodic solutions to convex and non coercive Hamiltonian systems ». Discrete & ; Continuous Dynamical Systems - A 12, n^o 5 (2005) : 983–96. http://dx.doi.org/10.3934/dcds.2005.12.983.

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Grotta-Ragazzo, C., et Pedro A. S. Salomão. « Global surfaces of section in non-regular convex energy levels of Hamiltonian systems ». Mathematische Zeitschrift 255, n^o 2 (22 août 2006) : 323–34. http://dx.doi.org/10.1007/s00209-006-0026-y.

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Giuliani, Filippo. « Transfers of energy through fast diffusion channels in some resonant PDEs on the circle ». Discrete & ; Continuous Dynamical Systems 41, n^o 11 (2021) : 5057. http://dx.doi.org/10.3934/dcds.2021068.

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In this paper we consider two classes of resonant Hamiltonian PDEs on the circle with non-convex (respect to actions) first order resonant Hamiltonian. We show that, for appropriate choices of the nonlinearities we can find time-independent linear potentials that enable the construction of solutions that undergo a prescribed growth in the Sobolev norms. The solutions that we provide follow closely the orbits of a nonlinear resonant model, which is a good approximation of the full equation. The non-convexity of the resonant Hamiltonian allows the existence of fast diffusion channels along which the orbits of the resonant model experience a large drift in the actions in the optimal time. This phenomenon induces a transfer of energy among the Fourier modes of the solutions, which in turn is responsible for the growth of higher order Sobolev norms.

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Corsi, Livia, Roberto Feola et Guido Gentile. « Lower-Dimensional Invariant Tori for Perturbations of a Class of Non-convex Hamiltonian Functions ». Journal of Statistical Physics 150, n^o 1 (janvier 2013) : 156–80. http://dx.doi.org/10.1007/s10955-012-0682-8.

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Bardi, Martino, et Markus Fischer. « On non-uniqueness and uniqueness of solutions in finite-horizon Mean Field Games ». ESAIM : Control, Optimisation and Calculus of Variations 25 (2019) : 44. http://dx.doi.org/10.1051/cocv/2018026.

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This paper presents a class of evolutive Mean Field Games with multiple solutions for all time horizons T and convex but non-smooth Hamiltonian H, as well as for smooth H and T large enough. The phenomenon is analysed in both the PDE and the probabilistic setting. The examples are compared with the current theory about uniqueness of solutions. In particular, a new result on uniqueness for the MFG PDEs with small data, e.g., small T, is proved. Some results are also extended to MFGs with two populations.

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KRITCHEVSKI, E., et S. STARR. « THE EXTENDED VARIATIONAL PRINCIPLE FOR MEAN-FIELD, CLASSICAL SPIN SYSTEMS ». Reviews in Mathematical Physics 17, n^o 10 (novembre 2005) : 1209–39. http://dx.doi.org/10.1142/s0129055x05002510.

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The purpose of this article is to obtain a better understanding of the extended variational principle (EVP). The EVP is a formula for the thermodynamic pressure of a statistical mechanical system as a limit of a sequence of minimization problems. It was developed for disordered mean-field spin systems, spin systems where the underlying Hamiltonian is itself random, and whose distribution is permutation invariant. We present the EVP in the simpler setting of classical mean-field spin systems, where the Hamiltonian is non-random and symmetric. The EVP essentially solves these models. We compare the EVP with another method for mean-field spin systems: the self-consistent mean-field equations. The two approaches lead to dual convex optimization problems. This is a new connection, and it permits a generalization of the EVP.

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Amick, C. J., et J. F. Toland. « Points of egress in problems of Hamiltonian dynamics ». Mathematical Proceedings of the Cambridge Philosophical Society 109, n^o 2 (mars 1991) : 405–17. http://dx.doi.org/10.1017/s030500410006984x.

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First we consider an elementary though delicate question about the trajectory in ℝn of a particle in a conservative field of force whose dynamics are governed by the equationHere the potential function V is supposed to have Lipschitz continuous first derivative at every point of ℝn. This is a natural assumption which ensures that the initial-value problem is well-posed. We suppose also that there is a closed convex set C with non-empty interior C° such that V ≥ 0 in C and V = 0 on the boundary ∂C of C. It is noteworthy that we make no assumptions about the degeneracy (or otherwise) of V on ∂C (i.e. whether ∇V = 0 on ∂C, or not); thus ∂C is a Lipschitz boundary because of its convexity but not necessarily any smoother in general. We remark also that there are no convexity assumptions about V and nothing is known about the behaviour of V outside C.

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Cirant, Marco, et Alessio Porretta. « Long time behavior and turnpike solutions in mildly non-monotone mean field games ». ESAIM : Control, Optimisation and Calculus of Variations 27 (2021) : 86. http://dx.doi.org/10.1051/cocv/2021077.

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We consider mean field game systems in time-horizon (0, T), where the individual cost functional depends locally on the density distribution of the agents, and the Hamiltonian is locally uniformly convex. We show that, even if the coupling cost functions are mildly non-monotone, then the system is still well posed due to the effect of individual noise. The rate of anti-monotonicity (i.e. the aggregation rate of the cost functions) which can be afforded depends on the intensity of the diffusion and on global bounds of solutions. We give applications to either the case of globally Lipschitz Hamiltonians or the case of quadratic Hamiltonians and couplings having mild growth. Under similar conditions, we investigate the long time behavior of solutions and we give a complete description of the ergodic and long term properties of the system. In particular we prove: (i) the turnpike property of solutions in the finite (long) horizon (0, T), (ii) the convergence of the system from (0, T) towards (0, ∞), (iii) the vanishing discount limit of the infinite horizon problem and the long time convergence towards the ergodic stationary solution. This way we extend previous results which were known only for the case of monotone and smoothing couplings; our approach is self-contained and does not need the use of the linearized system or of the master equation.

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Khanin, Konstantin, et Andrei Sobolevski. « Particle dynamics inside shocks in Hamilton–Jacobi equations ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 368, n^o 1916 (13 avril 2010) : 1579–93. http://dx.doi.org/10.1098/rsta.2009.0283.

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The characteristic curves of a Hamilton–Jacobi equation can be seen as action-minimizing trajectories of fluid particles. For non-smooth ‘viscosity’ solutions, which give rise to discontinuous velocity fields, this description is usually pursued only up to the moment when trajectories hit a shock and cease to minimize the Lagrangian action. In this paper we show that, for any convex Hamiltonian, there exists a uniquely defined canonical global non-smooth coalescing flow that extends particle trajectories and determines the dynamics inside shocks. We also provide a variational description of the corresponding effective velocity field inside shocks, and discuss the relation to the ‘dissipative anomaly’ in the limit of vanishing viscosity.

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Ennaji, Hamza, Noureddine Igbida et Van Thanh Nguyen. « Beckmann-type problem for degenerate Hamilton-Jacobi equations ». Quarterly of Applied Mathematics 80, n^o 2 (21 décembre 2021) : 201–20. http://dx.doi.org/10.1090/qam/1606.

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The aim of this note is to give a Beckmann-type problem as well as the corresponding optimal mass transportation problem associated with a degenerate Hamilton-Jacobi equation H ( x , ∇ u ) = 0 , H(x,\nabla u)=0, coupled with non-zero Dirichlet condition u = g u=g on ∂ Ω \partial \Omega . In this article, the Hamiltonian H H is continuous in both arguments, coercive and convex in the second, but not enjoying any property of existence of a smooth strict sub-solution. We also provide numerical examples to validate the correctness of theoretical formulations.

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Mahmudov, Elimhan. « Optimization of Lagrange problem with higher order differential inclusions and endpoint constraints ». Filomat 32, n^o 7 (2018) : 2367–82. http://dx.doi.org/10.2298/fil1807367m.

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In the paper minimization of a Lagrange type cost functional over the feasible set of solutions of higher order differential inclusions with endpoint constraints is studied. Our aim is to derive sufficient conditions of optimality for m th-order convex and non-convex differential inclusions. The sufficient conditions of optimality containing the Euler-Lagrange and Hamiltonian type inclusions as a result of endpoint constraints are accompanied by so-called ?endpoint? conditions. Here the basic apparatus of locally adjoint mappings is suggested. An application from the calculus of variations is presented and the corresponding Euler-Poisson equation is derived. Moreover, some higher order linear optimal control problems with quadratic cost functional are considered and the corresponding Weierstrass-Pontryagin maximum principle is constructed. Also at the end of the paper some characteristic features of the obtained result are illustrated by example with second order linear differential inclusions.

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Chen, Qinbo, et Rafael de la Llave. « Analytic genericity of diffusing orbits in a priori unstable Hamiltonian systems ». Nonlinearity 35, n^o 4 (9 mars 2022) : 1986–2019. http://dx.doi.org/10.1088/1361-6544/ac50bb.

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Abstract The genericity of Arnold diffusion in the analytic category is an open problem. In this paper, we study this problem in the following a priori unstable Hamiltonian system with a time-periodic perturbation H ε ( p , q , I , φ , t ) = h ( I ) + ∑ i = 1 n ± 1 2 p i 2 + V i ( q i ) + ε H 1 ( p , q , I , φ , t ) , where ( p , q ) ∈ R n × T n , ( I , φ ) ∈ R d × T d with n, d ⩾ 1, V i are Morse potentials, and ɛ is a small non-zero parameter. The unperturbed Hamiltonian is not necessarily convex, and the induced inner dynamics does not need to satisfy a twist condition. Using geometric methods we prove that Arnold diffusion occurs for generic analytic perturbations H 1. Indeed, the set of admissible H 1 is C ω dense and C 3 open (a fortiori, C ω open). Our perturbative technique for the genericity is valid in the C k topology for all k ∈ [3, ∞) ∪ {∞, ω}.

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De Blasi, Irene, Alessandra Celletti et Christos Efthymiopoulos. « Satellites’ orbital stability through normal forms ». Proceedings of the International Astronomical Union 15, S364 (octobre 2021) : 146–51. http://dx.doi.org/10.1017/s174392132100137x.

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AbstractA powerful tool to investigate the stability of the orbits of natural and artificial bodies is represented by perturbation theory, which allows one to provide normal form estimates for nearly-integrable problems in Celestial Mechanics. In particular, we consider the orbital stability of point-mass satellites moving around the Earth. On the basis of the J2 model, we investigate the stability of the semimajor axis. Using a secular Hamiltonian model including also lunisolar perturbations, the so-called geolunisolar model, we study the stability of the other orbital elements, namely the eccentricity and the inclination. We finally discuss the applicability of Nekhoroshev’s theorem on the exponential stability of the action variables. To this end, we investigate the non-degeneracy properties of the J2 and geolunisolar models. We obtain that the J2 model satisfies a “three-jet” non-degeneracy condition, while the geolunisolar model is quasi-convex non-degenerate.

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Radjenovic, B., M. Radmilovic-Radjenovic et M. Mitric. « Application of the level set method on the non-convex Hamiltonians ». Facta universitatis - series : Physics, Chemistry and Technology 7, n^o 1 (2009) : 33–44. http://dx.doi.org/10.2298/fupct0901033r.

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Application of the level set method extended for the case of non-convex Hamiltonians is illustrated by the three dimensional (3D) simulation results of the profile evolution during anisotropic wet etching of silicon. Etching rate function is modeled on the basis of the silicon symmetry properties, by means of the interpolation technique using experimentally obtained values of the principal [100], [110], [111], and high index [311] directions in KOH solutions. The resulting level set equations are solved using an open source implementation of the sparse field method.

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Bounemoura, Abed, et Vadim Kaloshin. « Generic Fast Diffusion for a Class of Non-Convex Hamiltonians with Two Degrees of Freedom ». Moscow Mathematical Journal 14, n^o 2 (2014) : 181–203. http://dx.doi.org/10.17323/1609-4514-2014-14-2-181-203.

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Radjenović, Branislav, Jae Koo Lee et Marija Radmilović-Radjenović. « Sparse field level set method for non-convex Hamiltonians in 3D plasma etching profile simulations ». Computer Physics Communications 174, n^o 2 (janvier 2006) : 127–32. http://dx.doi.org/10.1016/j.cpc.2005.09.010.

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Aslani, Shahriar, et Patrick Bernard. « Normal Form Near Orbit Segments of Convex Hamiltonian Systems ». International Mathematics Research Notices, 18 janvier 2021. http://dx.doi.org/10.1093/imrn/rnaa344.

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Abstract In the study of Hamiltonian systems on cotangent bundles, it is natural to perturb Hamiltonians by adding potentials (functions depending only on the base point). This led to the definition of Mañé genericity [ 8]: a property is generic if, given a Hamiltonian $H$, the set of potentials $g$ such that $H+g$ satisfies the property is generic. This notion is mostly used in the context of Hamiltonians that are convex in $p$, in the sense that $\partial ^2_{pp} H$ is positive definite at each point. We will also restrict our study to this situation. There is a close relation between perturbations of Hamiltonians by a small additive potential and perturbations by a positive factor close to one. Indeed, the Hamiltonians $H+g$ and $H/(1-g)$ have the same level one energy surface, hence their dynamics on this energy surface are reparametrisation of each other, this is the Maupertuis principle. This remark is particularly relevant when $H$ is homogeneous in the fibers (which corresponds to Finsler metrics) or even fiberwise quadratic (which corresponds to Riemannian metrics). In these cases, perturbations by potentials of the Hamiltonian correspond, up to parametrisation, to conformal perturbations of the metric. One of the widely studied aspects is to understand to what extent the return map associated to a periodic orbit can be modified by a small perturbation. This kind of question depends strongly on the context in which they are posed. Some of the most studied contexts are, in increasing order of difficulty, perturbations of general vector fields, perturbations of Hamiltonian systems inside the class of Hamiltonian systems, perturbations of Riemannian metrics inside the class of Riemannian metrics, and Mañé perturbations of convex Hamiltonians. It is for example well known that each vector field can be perturbed to a vector field with only hyperbolic periodic orbits, this is part of the Kupka–Smale Theorem, see [ 5, 13] (the other part of the Kupka–Smale Theorem states that the stable and unstable manifolds intersect transversally; it has also been studied in the various settings mentioned above but will not be discussed here). In the context of Hamiltonian vector fields, the statement has to be weakened, but it remains true that each Hamiltonian can be perturbed to a Hamiltonian with only non-degenerate periodic orbits (including the iterated ones), see [ 11, 12]. The same result is true in the context of Riemannian metrics: every Riemannian metric can be perturbed to a Riemannian metric with only non-degenerate closed geodesics, this is the bumpy metric theorem, see [ 1, 2, 4]. The question was investigated only much more recently in the context of Mañé perturbations of convex Hamiltonians, see [ 9, 10]. It is proved in [ 10] that the same result holds: if $H$ is a convex Hamiltonian and $a$ is a regular value of $H$, then there exist arbitrarily small potentials $g$ such that all periodic orbits (including iterated ones) of $H+g$ at energy $a$ are non-degenerate. The proof given in [ 10] is actually rather similar to the ones given in papers on the perturbations of Riemannian metrics. In all these proofs, it is very useful to work in appropriate coordinates around an orbit segment. In the Riemannian case, one can use the so-called Fermi coordinates. In the Hamiltonian case, appropriate coordinates are considered in [ 10,Lemma 3.1] itself taken from [ 3, Lemma C.1]. However, as we shall detail below, the proof of this Lemma in [ 3], Appendix C, is incomplete, and the statement itself is actually wrong. Our goal in the present paper is to state and prove a corrected version of this normal form Lemma. Our proof is different from the one outlined in [ 3], Appendix C. In particular, it is purely Hamiltonian and does not rest on the results of [ 7] on Finsler metrics, as [ 3] did. Although our normal form is weaker than the one claimed in [ 10], it is actually sufficient to prove the main results of [ 6, 10], as we shall explain after the statement of Theorem 1, and probably also of the other works using [ 3, Lemma C.1].

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Bolten, M., O. T. Doganay, H. Gottschalk et K. Klamroth. « Non-convex shape optimization by dissipative Hamiltonian flows ». Engineering Optimization, 18 février 2024, 1–20. http://dx.doi.org/10.1080/0305215x.2024.2304135.

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Chau, Huy N., et Miklós Rásonyi. « Stochastic Gradient Hamiltonian Monte Carlo for non-convex learning ». Stochastic Processes and their Applications, avril 2022. http://dx.doi.org/10.1016/j.spa.2022.04.001.

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Ratiu, Tudor, Christophe Wacheux et Nguyen Zung. « Convexity of Singular Affine Structures and Toric-Focus Integrable Hamiltonian Systems ». Memoirs of the American Mathematical Society 287, n^o 1424 (juillet 2023). http://dx.doi.org/10.1090/memo/1424.

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This work is devoted to a systematic study of symplectic convexity for integrable Hamiltonian systems with elliptic and focus-focus singularities. A distinctive feature of these systems is that their base spaces are still smooth manifolds (with boundary and corners), analogous to the toric case, but their associated integral affine structures are singular, with non-trivial monodromy, due to focus singularities. We obtain a series of convexity results, both positive and negative, for such singular integral affine base spaces. In particular, near a focus singular point, they are locally convex and the local-global convexity principle still applies. They are also globally convex under some natural additional conditions. However, when the monodromy is sufficiently large, the local-global convexity principle breaks down and the base spaces can be globally non-convex, even for compact manifolds. As a surprising example, we construct a 2-dimensional “integral affine black hole”, which is locally convex but for which a straight ray from the center can never escape.

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Fabila-Monroy, Ruy, David Flores-Peñaloza, Clemens Huemer, Ferran Hurtado, Jorge Urrutia et David R. Wood. « On the chromatic number of some flip graphs ». Discrete Mathematics & ; Theoretical Computer Science Vol. 11 no. 2, Graph and Algorithms (1 janvier 2009). http://dx.doi.org/10.46298/dmtcs.460.

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Graphs and Algorithms International audience This paper studies the chromatic number of the following four flip graphs (under suitable definitions of a flip): the flip graph of perfect matchings of a complete graph of even order, the flip graph of triangulations of a convex polygon (the associahedron), the flip graph of non-crossing Hamiltonian paths of a set of points in convex position, and the flip graph of triangles in a convex point set. We give tight bounds for the latter two cases and upper bounds for the first two.

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De Blasi, Irene, Alessandra Celletti et Christos Efthymiopoulos. « Semi-Analytical Estimates for the Orbital Stability of Earth’s Satellites ». Journal of Nonlinear Science 31, n^o 6 (27 septembre 2021). http://dx.doi.org/10.1007/s00332-021-09738-w.

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AbstractNormal form stability estimates are a basic tool of Celestial Mechanics for characterizing the long-term stability of the orbits of natural and artificial bodies. Using high-order normal form constructions, we provide three different estimates for the orbital stability of point-mass satellites orbiting around the Earth. (i) We demonstrate the long-term stability of the semimajor axis within the framework of the $$J_2$$ J 2 problem, by a normal form construction eliminating the fast angle in the corresponding Hamiltonian and obtaining $${\mathcal {H}}_{J_2}$$ H J 2 . (ii) We demonstrate the stability of the eccentricity and inclination in a secular Hamiltonian model including lunisolar perturbations (the ‘geolunisolar’ Hamiltonian $${\mathcal {H}}_\mathrm{gls}$$ H gls ), after a suitable reduction of the Hamiltonian to the Laplace plane. (iii) We numerically examine the convexity and steepness properties of the integrable part of the secular Hamiltonian in both the $${\mathcal {H}}_{J_2}$$ H J 2 and $${\mathcal {H}}_\mathrm{gls}$$ H gls models, which reflect necessary conditions for the holding of Nekhoroshev’s theorem on the exponential stability of the orbits. We find that the $${\mathcal {H}}_{J_2}$$ H J 2 model is non-convex, but satisfies a ‘three-jet’ condition, while the $${\mathcal {H}}_\mathrm{gls}$$ H gls model restores quasi-convexity by adding lunisolar terms in the Hamiltonian’s integrable part.

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Giambò, Roberto, Fabio Giannoni et Paolo Piccione. « On the Least Action Principle – Hamiltonian Dynamics on Fixed Energy Levels in the Non-convex Case ». Advanced Nonlinear Studies 6, n^o 2 (1 janvier 2006). http://dx.doi.org/10.1515/ans-2006-0208.

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AbstractWe review the classical Principle of the Least Action in a general context where the Hamilton functionH is possibly non-convex. We show how the van Groesen [6] principle follows as a particular case where H is hyperregular and of homogeneous type. Homogeneous scalar field spacetimes in spherical symmetry are derived as an application.

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Keller, Chaya, et Yael Stein. « Blockers for Triangulations of a Convex Polygon and a Geometric Maker-Breaker Game ». Electronic Journal of Combinatorics 27, n^o 4 (16 octobre 2020). http://dx.doi.org/10.37236/7205.

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Let $G$ be a complete convex geometric graph whose vertex set $P$ forms a convex polygon $C$, and let $\mathcal{F}$ be a family of subgraphs of $G$. A blocker for $\mathcal{F}$ is a set of diagonals of $C$, of smallest possible size, that contains a common edge with every element of $\mathcal{F}$. Previous works determined the blockers for various families $\mathcal{F}$ of non-crossing subgraphs, including the families of all perfect matchings, all spanning trees, all Hamiltonian paths, etc. In this paper we present a complete characterization of the family $\mathcal{B}$ of blockers for the family $\mathcal{T}$ of triangulations of $C$. In particular, we show that $|\mathcal{B}|=F_{2n-8}$, where $F_k$ is the $k$'th element in the Fibonacci sequence and $n=|P|$. We use our characterization to obtain a tight result on a geometric Maker-Breaker game in which the board is the set of diagonals of a convex $n$-gon $C$ and Maker seeks to occupy a triangulation of $C$. We show that in the $(1:1)$ triangulation game, Maker can ensure a win within $n-3$ moves, and that in the $(1:2)$ triangulation game, Breaker can ensure a win within $n-3$ moves. In particular, the threshold bias for the game is $2$.

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Wen, Xueda, Yingfei Gu, Ashvin Vishwanath et Ruihua Fan. « Periodically, Quasi-periodically, and Randomly Driven Conformal Field Theories (II) : Furstenberg's Theorem and Exceptions to Heating Phases ». SciPost Physics 13, n^o 4 (5 octobre 2022). http://dx.doi.org/10.21468/scipostphys.13.4.082.

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In this sequel (to [Phys. Rev. Res. 3, 023044(2021)], arXiv:2006.10072), we study randomly driven (1+1)(1+1) dimensional conformal field theories (CFTs), a family of quantum many-body systems with soluble non-equilibrium quantum dynamics. The sequence of driving Hamiltonians is drawn from an independent and identically distributed random ensemble. At each driving step, the deformed Hamiltonian only involves the energy-momentum density spatially modulated at a single wavelength and therefore induces a Möbius transformation on the complex coordinates. The non-equilibrium dynamics is then determined by the corresponding sequence of Möbius transformations, from which the Lyapunov exponent \lambda_LλL is defined. We use Furstenberg’s theorem to classify the dynamical phases and show that except for a few exceptional points that do not satisfy Furstenberg’s criteria, the random drivings always lead to a heating phase with the total energy growing exponentially in the number of driving steps nn and the subsystem entanglement entropy growing linearly in nn with a slope proportional to central charge cc and the Lyapunov exponent \lambda_LλL. On the contrary, the subsystem entanglement entropy at an exceptional point could grow as \sqrt{n}n while the total energy remains to grow exponentially. In addition, we show that the distributions of the operator evolution and the energy density peaks are also useful characterizations to distinguish the heating phase from the exceptional points: the heating phase has both distributions to be continuous, while the exceptional points could support finite convex combinations of Dirac measures depending on their specific type. In the end, we compare the field theory results with the lattice model calculations for both the entanglement and energy evolution and find remarkably good agreement.

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Tian, Yuzhou, Qiaoling Wei et Meirong Zhang. « On the polynomial integrability of the critical systems for optimal eigenvalue gaps ». Journal of Mathematical Physics 64, n^o 9 (1 septembre 2023). http://dx.doi.org/10.1063/5.0140966.

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This exploration consists of two parts. First, we will deduce a family of critical systems consisting of nonlinear ordinary differential equations, indexed by the exponent p ∈ (1, ∞) of the Lebesgue spaces concerned. These systems can be used to obtain the optimal lower or upper bounds for eigenvalue gaps of Sturm–Liouville operators and are equivalent to non-convex Hamiltonian systems of two degrees of freedom. Second, with appropriate choices of exponents p, the critical systems are polynomial systems in four dimensions. These systems will be investigated from two aspects. The first one is that by applying the canonical transformation and the Darboux polynomial, we obtain the necessary and sufficient conditions for polynomial integrability of these polynomial critical systems. As a special example, we conclude that the system with p = 2 is polynomial completely integrable in the sense of Liouville. The second is that the linear stability of isolated singular points is characterized. By performing the Poincaré cross section technique, we observe that the systems have very rich dynamical behaviors, including periodic trajectories, quasi-periodic trajectories, and chaos.

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TAPIA-GARCÍA, SEBASTIÁN. « REGULARITY OF AML FUNCTIONS IN TWO-DIMENSIONAL NORMED SPACES ». Journal of the Australian Mathematical Society, 20 mai 2022, 1–25. http://dx.doi.org/10.1017/s1446788722000088.

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Abstract Savin [‘ $\mathcal {C}^{1}$ regularity for infinity harmonic functions in two dimensions’, Arch. Ration. Mech. Anal.3(176) (2005), 351–361] proved that every planar absolutely minimizing Lipschitz (AML) function is continuously differentiable whenever the ambient space is Euclidean. More recently, Peng et al. [‘Regularity of absolute minimizers for continuous convex Hamiltonians’, J. Differential Equations274 (2021), 1115–1164] proved that this property remains true for planar AML functions for certain convex Hamiltonians, using some Euclidean techniques. Their result can be applied to AML functions defined in two-dimensional normed spaces with differentiable norm. In this work we develop a purely non-Euclidean technique to obtain the regularity of planar AML functions in two-dimensional normed spaces with differentiable norm.

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