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Автор: Grafiati

Опубліковано: 7 липня 2024

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1

Calmet, Xavier, Roberto Casadio, and Folkert Kuipers. "Singularities in quantum corrected space-times." Physics Letters B 807 (August 2020): 135605. http://dx.doi.org/10.1016/j.physletb.2020.135605.

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2

Davis, Simon. "Desingularization of Black Hole Space-Times." Bulletin of Pure and Applied Sciences – Physics 42, no. 1 (June 17, 2023): 6–34. http://dx.doi.org/10.48165/bpas.2023.42d.1.2.

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The desingularization of a class of black hole space-times arising as solutions to the string equations is considered in connection with the consistency of the quantum theory and the description of nonperturbative states with quantum numbers from the particle spectrum. The geometry arising in an extreme limit of one of the singular solutions to the gravitational field equations is demonstrated to be a background of N = 2 string theory. The positivity of the masses in the particle spectrum is proven through quasilocal integrals near the resolved singularities in these limits of black hole space-times.

3

KONKOWSKI, D. A., and T. M. HELLIWELL. "QUANTUM SINGULARITIES IN STATIC AND CONFORMALLY STATIC SPACE-TIMES." International Journal of Modern Physics A 26, no. 22 (September 10, 2011): 3878–88. http://dx.doi.org/10.1142/s0217751x11054334.

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The definition of quantum singularity is extended from static space-times to conformally static space-times. After the usual definitions of classical and quantum singularities are reviewed, examples of quantum singularities in static space-times are given. These include asymptotically power-law space-times, space-times with diverging higher-order differential invariants, and a space-time with a 2-sphere singularity. The theory behind quantum singularities in conformally static space-times is followed by an example, a Friedmann-Robertson-Walker space-time with cosmic string. The paper concludes by discussing areas of future research.

4

KONKOWSKI, D. A., and T. M. HELLIWELL. "QUANTUM SINGULARITIES IN STATIC AND CONFORMALLY STATIC SPACE-TIMES." International Journal of Modern Physics: Conference Series 03 (January 2011): 364–74. http://dx.doi.org/10.1142/s2010194511001462.

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The definition of quantum singularity is extended from static space-times to conformally static space-times. After the usual definitions of classical and quantum singularities are reviewed, examples of quantum singularities in static space-times are given. These include asymptotically power-law space-times, space-times with diverging higher-order differential invariants, and a space-time with a 2-sphere singularity. The theory behind quantum singularities in conformally static space-times is followed by an example, a Friedmann-Robertson-Walker space-time with cosmic string. The paper concludes by discussing areas of future research.

5

Parmeggiani, Claudio. "Quantum fields and gravity: Expanding space-times." International Journal of Modern Physics A 35, no. 02n03 (January 30, 2020): 2040039. http://dx.doi.org/10.1142/s0217751x20400394.

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We discuss a proposal for a somewhat new formulation of quantum field theory (set in a four-dimensional manifold, the space-time) that includes an analysis of its implications for the evolution of Einstein-Friedmann cosmological models. The proposed theory displays two peculiar features: (i) a local Hilbert-Fock space is associated with each space-time point: we are dealing with a vector bundle whose fibers are Hilbert spaces; the operator-valued sections of the bundle are the quantum fields; (ii) the vacuum energy density is finite, being regularized in a space-time curvature dependent way, independently at each point. In fact everything is finite: self-masses, self-charges, quantum fluctuations: they depend on the space-time curvature and diverge only for a flat metric. In an Einstein-Friedmann model the vacuum (zero-point) energy density is consequently time-dependent and in general not negligible. Then it is shown that, for some choices of the parameters of the theory, the big-bang singularity is resolved and replaced by a bounce driven by the vacuum energy density, which becomes (very) large and negative near the bounce (negative by the contribution of the Fermi fields). But for large times (now, say) the Bose fields’ positive vacuum energy eventually overcomes the negative one and we are finally left with the present vacuum energy: positive and reasonably small.

6

Hudson, R. L. "Stop times in Fock space quantum probability." Stochastics 79, no. 3-4 (June 2007): 383–91. http://dx.doi.org/10.1080/17442500601078966.

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7

Balachandran, AP. "Quantum space-times in the year 2002." Pramana 59, no. 2 (August 2002): 359–68. http://dx.doi.org/10.1007/s12043-002-0128-y.

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8

Sánchez, N. "Quantum string theory in curved space-times." Astronomische Nachrichten: A Journal on all Fields of Astronomy 311, no. 4 (1990): 231–38. http://dx.doi.org/10.1002/asna.2113110408.

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9

Janssen, Daan W. "Quantum Fields on Semi-globally Hyperbolic Space–Times." Communications in Mathematical Physics 391, no. 2 (February 21, 2022): 669–705. http://dx.doi.org/10.1007/s00220-022-04328-7.

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AbstractWe introduce a class of space–times modeling singular events such as evaporating black holes and topology changes, which we dub as semi-globally hyperbolic space–times. On these space–times we aim to study the existence of reasonable quantum field theories. We establish a notion of linear scalar quantum field theories on these space–times, show how such a theory might be constructed and introduce notions of global dynamics on these theories. Applying these contructions to both black hole evaporation and topology changing space–times, we find that existence of algebras can be relatively easily established, while the existence of reasonable states on these algebras remains an unsolved problem.

10

SKÁKALA, JOZEF, and MATT VISSER. "PSEUDO-FINSLERIAN SPACE–TIMES AND MULTIREFRINGENCE." International Journal of Modern Physics D 19, no. 07 (July 2010): 1119–46. http://dx.doi.org/10.1142/s0218271810017172.

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Ongoing searches for a quantum theory of gravity have repeatedly led to the suggestion that space–time might ultimately be anisotropic (Finsler-like) and/or exhibit multirefringence (multiple signal cones). Multiple (and even anisotropic) signal cones can be easily dealt with in a unified manner, by writing down a single Fresnel equation to simultaneously encode all signal cones in an even-handed manner. Once one gets off the signal cone and attempts to construct a full multirefringent space–time metric the situation becomes more problematic. In the multirefringent case we shall report a significant no-go result: in multirefringent models there is no simple or compelling way to construct any unifying notion of pseudo-Finsler space–time metric, different from a monorefringenent model, where the signal cone structure plus a conformal factor completely specifies the full pseudo-Riemannian metric. To throw some light on this situation we use an analog model where both anisotropy and multirefringence occur simultaneously: biaxial birefringent crystal. But the significance of our results extends beyond the optical framework in which (purely for pedagogical reasons) we are working, and has implications for any attempt at introducing multirefringence and intrinsic anisotropies to any model of quantum gravity that has a low energy manifold-like limit.

11

Ding, Shuxue, Yasushige Maeda, and Masaru Siino. "Four dimensional quantum topology changes of space–times." Journal of Mathematical Physics 37, no. 11 (November 1996): 5611–26. http://dx.doi.org/10.1063/1.531725.

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12

Balakumar, Visakan, Elizabeth Winstanley, Rafael P. Bernar, and Luís C. B. Crispino. "Quantum superradiance on static black hole space-times." Physics Letters B 811 (December 2020): 135904. http://dx.doi.org/10.1016/j.physletb.2020.135904.

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13

Balakumar, Visakan, Rafael Bernar, and Elizabeth Winstanley. "Superradiance and quantum states on black hole space-times." Journal of Physics: Conference Series 2531, no. 1 (June 1, 2023): 012011. http://dx.doi.org/10.1088/1742-6596/2531/1/012011.

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Abstract We consider the definition of the Boulware and Hartle-Hawking states for quantum fields on black hole space-times. The properties of these states on a Schwarzschild black hole have been understood for many years, but neither of these states has a direct analogue on a Kerr black hole. We show how superradiant modes play an important role in the definition of quantum states on Kerr. Superradiance is also present on static black hole space-times, in particular for a charged scalar field on a Reissner-Nordström black hole. We explore whether analogues of the Boulware and Hartle-Hawking states exist in this situation.

14

HUSAIN, VIQAR, and JORGE PULLIN. "QUANTUM THEORY OF SPACE-TIMES WITH ONE KILLING FIELD." Modern Physics Letters A 05, no. 10 (April 20, 1990): 733–41. http://dx.doi.org/10.1142/s0217732390000834.

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We describe the canonical quantization of Einstein gravity for space-times with one killing vector field. We use the new canonical variables introduced by Ashtekar. Both the connection and loop space representations for the quantum theory are considered. We find that the physical state space has a characterization in terms of equivalence classes of Eulerian graphs.

15

Padavic-Callaghan, Karmela. "Quantum magnet is billions of times colder than space." New Scientist 255, no. 3403 (September 2022): 13. http://dx.doi.org/10.1016/s0262-4079(22)01613-x.

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16

Müller, Thomas. "A branching space-times view on quantum error correction." Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 38, no. 3 (September 2007): 635–52. http://dx.doi.org/10.1016/j.shpsb.2007.05.003.

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17

de Vega, H. J., and N. Sánchez. "Quantum dynamics of strings in black hole space times." Nuclear Physics B 309, no. 3 (November 1988): 552–76. http://dx.doi.org/10.1016/0550-3213(88)90458-0.

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18

Rabochaya, Yevgeniya, and Sergio Zerbini. "Quantum Detectors in Generic Non Flat FLRW Space-Times." International Journal of Theoretical Physics 55, no. 5 (December 29, 2015): 2682–96. http://dx.doi.org/10.1007/s10773-015-2902-x.

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19

ALENCAR, G., I. GUEDES, R. R. LANDIM, and R. N. COSTA FILHO. "QUANTUM KALB–RAMOND FIELD IN D-DIMENSIONAL DE SITTER SPACE–TIMES." International Journal of Modern Physics A 28, no. 05n06 (March 10, 2013): 1350011. http://dx.doi.org/10.1142/s0217751x13500115.

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In this work, we investigate the quantum theory of the Kalb–Ramond fields propagating in D-dimensional de Sitter space–times using the dynamic invariant method developed by Lewis and Riesenfeld [J. Math. Phys.10, 1458 (1969)] to obtain the solution of the time-dependent Schrödinger equation. The wave function is written in terms of a c-number quantity satisfying the Milne–Pinney equation, whose solution can be expressed in terms of two independent solutions of the respective equation of motion. We obtain the exact solution for the quantum Kalb–Ramond field in the de Sitter background and discuss its relation with the Cremmer–Scherk–Kalb–Ramond model.

20

PIEDRA, OWEN PAVEL FERNANDEZ, and JEFERSON de OLIVEIRA. "VACUUM POLARIZATION EFFECTS ON QUASINORMAL MODES IN ELECTRICALLY CHARGED BLACK HOLE SPACE–TIMES." International Journal of Modern Physics D 19, no. 01 (January 2010): 63–78. http://dx.doi.org/10.1142/s0218271810016257.

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We investigate the influence of vacuum polarization of quantum massive fields on the scalar sector of quasinormal modes in spherically symmetric black holes. We consider the evolution of a massless scalar field on the space–time corresponding to a charged semiclassical black hole, consisting of the quantum-corrected geometry of a Reissner–Nordström black hole dressed by a quantum massive scalar field in the large mass limit. Using a sixth order WKB approach we find a shift in the quasinormal mode frequencies due to vacuum polarization.

21

Kang, Yuanbao. "Quantum stopping times stochastic integral in the interacting Fock space." Journal of Mathematical Physics 56, no. 8 (August 2015): 083508. http://dx.doi.org/10.1063/1.4921886.

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22

Brown, M. R., A. C. Ottewill, and Don N. Page. "Conformally invariant quantum field theory in static Einstein space-times." Physical Review D 33, no. 10 (May 15, 1986): 2840–50. http://dx.doi.org/10.1103/physrevd.33.2840.

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23

Binosi, Daniele, and Sergio Zerbini. "Quantum scalar field inD-dimensional static black hole space–times." Journal of Mathematical Physics 40, no. 10 (October 1999): 5106–16. http://dx.doi.org/10.1063/1.533018.

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24

Keyl, Michael. "On Causal Compatibility of Quantum Field Theories and Space-Times." Communications in Mathematical Physics 195, no. 1 (July 1, 1998): 15–28. http://dx.doi.org/10.1007/s002200050377.

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25

Najmi, A. H., and A. C. Ottewill. "A constraint on physical quantum states in cosmological space-times." General Relativity and Gravitation 17, no. 6 (June 1985): 573–78. http://dx.doi.org/10.1007/bf00763050.

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26

Kent, Adrian. "Lorentzian quantum reality: postulates and toy models." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 373, no. 2047 (August 6, 2015): 20140241. http://dx.doi.org/10.1098/rsta.2014.0241.

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We describe postulates for a novel realist version of relativistic quantum theory or quantum field theory in Minkowski space and other background space–times, and illustrate their application with toy models.

27

Cotaescu, Ion I. "Canonical quantization of the covariant fields on de Sitter space–times." International Journal of Modern Physics A 33, no. 08 (March 20, 2018): 1830007. http://dx.doi.org/10.1142/s0217751x18300077.

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The properties of the covariant quantum fields on de Sitter space–times are investigated focusing on the isometry generators and Casimir operators in order to establish the equivalence among the covariant representations and the unitary irreducible ones of the de Sitter isometry group. For the Dirac quantum field, it is shown that the spinor covariant representation, transforming the Dirac field under de Sitter isometries, is equivalent with a direct sum of two unitary irreducible representations of the [Formula: see text] group, transforming alike the particle and antiparticle field operators in momentum representation. Their basis generators and Casimir operators are written down finding that the covariant representations are equivalent with unitary irreducible ones from the principal series whose canonical weights are determined by the fermion mass and spin.

28

Singha Roy, Subhamoy. "Quantum Field Theory on Noncommutative Curved Space-times and Noncommutative Gravity." American Journal of Science, Engineering and Technology 6, no. 4 (2021): 94. http://dx.doi.org/10.11648/j.ajset.20210604.11.

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29

Kutach, Douglas. "A Connection between Minkowski and Galilean Space‐times in Quantum Mechanics." International Studies in the Philosophy of Science 24, no. 1 (March 2010): 15–29. http://dx.doi.org/10.1080/02698590903467093.

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30

Pitelli, Paulo M., and Patricio S. Letelier. "Quantum singularities in space-times with spherical and cylindrical topological defects." Journal of Mathematical Physics 48, no. 9 (September 2007): 092501. http://dx.doi.org/10.1063/1.2779952.

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31

Buchbinder, I. L., G. de Berredo-Peixoto, and I. L. Shapiro. "Quantum effects in softly broken gauge theories in curved space–times." Physics Letters B 649, no. 5-6 (June 2007): 454–62. http://dx.doi.org/10.1016/j.physletb.2007.04.039.

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32

VAN RAAMSDONK, MARK. "BUILDING UP SPACE–TIME WITH QUANTUM ENTANGLEMENT." International Journal of Modern Physics D 19, no. 14 (December 2010): 2429–35. http://dx.doi.org/10.1142/s0218271810018529.

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In this essay, we argue that the emergence of classically connected space–times is intimately related to the quantum entanglement of degrees of freedom in a nonperturbative description of quantum gravity. Disentangling the degrees of freedom associated with two regions of space–time results in these regions pulling apart and pinching off from each other in a way that can be quantified by standard measures of entanglement.

33

ROSALES, J. L. "VACUUM DECAY VIA LORENTZIAN WORMHOLES." International Journal of Modern Physics A 13, no. 07 (March 20, 1998): 1191–99. http://dx.doi.org/10.1142/s0217751x98000548.

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We speculate about the space–time description due to the presence of Lorentzian worm-holes (handles in space–time joining two distant regions or other universes) in quantum gravity. The semiclassical rate of production of these Lorentzian wormholes in Reissner–Nordström space–times is calculated as a result of the spontaneous decay of vacuum due to a real tunneling configuration. In the magnetic case it only depends on the value of the field theoretical fine structure constant. We predict that the quantum probability corresponding to the nucleation of such geodesically complete space–times should be acutally negligible in our physical Universe.

34

Hollmann, Helia. "A harmonic space approach to quantum gravity of stationary space–times with SO(3) symmetry." Journal of Mathematical Physics 39, no. 11 (November 1998): 6066–85. http://dx.doi.org/10.1063/1.532613.

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35

DUNNE, GERALD V., and CARLO A. TRUGENBERGER. "SCHRÖDINGER REPRESENTATION FOR ABELIAN CHERN-SIMONS THEORIES ON NON-TRIVIAL SPACE-TIMES." Modern Physics Letters A 04, no. 17 (September 10, 1989): 1635–44. http://dx.doi.org/10.1142/s0217732389001866.

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We consider the U(1) Chern-Simons theory on three-manifolds of the form R×Σ, where Σ is a compact Riemann surface of genus g, and quantize the theory in the functional Schrödinger representation. Imposing gauge invariance at the quantum level requires the quantization of the overall normalization parameter k of the action and restricts the Hilbert space to a finite kg-dimensional space of functions on a g-dimensional configuration space. Gauge transformations are realized with a 1-cocycle and the theory is characterized by 2g vacuum angles. We consider the gauge- and coordinate-invariant fixed time operators of the theory, the quantum holonomy operators for closed curves C on Σ, and show that their eigenvalues on physical states are not completely determined by the homology class of C. Rather, there is an additional phase contribution fixed by the oriented self-intersection number of C.

36

Moalem, A., and A. Gersten. "Common Features of Free Particle Wave Functions in Curved Space-times." Journal of Physics: Conference Series 2482, no. 1 (May 1, 2023): 012003. http://dx.doi.org/10.1088/1742-6596/2482/1/012003.

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Abstract Quantum equations for massless particles of any spin and for massive spin one-half particles are considered in curved space-times. It is demonstrated that in stationary axially symmetric space-times the angular wave functions up to a normalization function are the same as in a Minkowski space-time. The radial wave functions satisfy second order nonhomogeneous differential equations with three nonhomogeneous terms which depend in a unique form on the ratio of time to space curvatures. For a Dirac spin one-half particle, in addition to these three terms a fourth term which depends on the particle rest mass is added.

37

Srivastava, Manu, and S. Shankaranarayanan. "Non-trivial quantum fluctuations in asymptotically non-flat black-hole space–times." Annals of Physics 440 (May 2022): 168829. http://dx.doi.org/10.1016/j.aop.2022.168829.

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38

Najmi, Amir-Homayoon, and Adrian C. Ottewill. "Quantum states and the Hadamard form. III. Constraints in cosmological space-times." Physical Review D 32, no. 8 (October 15, 1985): 1942–48. http://dx.doi.org/10.1103/physrevd.32.1942.

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39

Ho, Pei-Ming, Sanjaye Ramgoolam, and Radu Tatar. "Quantum space-times and finite effects in 4D super Yang–Mills theories." Nuclear Physics B 573, no. 1-2 (May 2000): 364–76. http://dx.doi.org/10.1016/s0550-3213(99)00819-6.

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40

Allen, Bruce, and Adrian C. Ottewill. "Effects of curvature couplings for quantum fields on cosmic-string space-times." Physical Review D 42, no. 8 (October 15, 1990): 2669–77. http://dx.doi.org/10.1103/physrevd.42.2669.

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41

SHOJAI, FATIMAH, and MEHDI GOLSHANI. "ON THE GEOMETRIZATION OF BOHMIAN MECHANICS: A NEW APPROACH TO QUANTUM GRAVITY." International Journal of Modern Physics A 13, no. 04 (February 10, 1998): 677–93. http://dx.doi.org/10.1142/s0217751x98000305.

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In this paper, a new approach to quantum gravity is presented in which the de-Broglie–Bohm quantum theory of motion is geometrized. This way of considering quantum gravity leads automatically to the fact that the quantum effects are contained in the conformal degree of freedom of the space–time metric. The present theory is then applied to the maximally symmetric space–time of cosmology, and it is observed that it is possible to avoid the initial singularity, while at large times the correct classical limit emerges.

42

RAMÓN MEDRANO, M., and N. G. SÁNCHEZ. "SEMICLASSICAL AND QUANTUM BLACK HOLES AND THEIR EVAPORATION, DE SITTER AND ANTI-DE SITTER REGIMES, GRAVITATIONAL AND STRING PHASE TRANSITIONS." International Journal of Modern Physics A 22, no. 32 (December 30, 2007): 6089–131. http://dx.doi.org/10.1142/s0217751x07038669.

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An effective string theory in physically relevant cosmological and black hole space–times is reviewed. Explicit computations of the quantum string entropy, partition function and quantum string emission by black holes (Schwarzschild, rotating, charged, asymptotically flat, de Sitter dS and anti-de Sitter AdS space–times) in the framework of effective string theory in curved backgrounds provide an amount of new quantum gravity results as: (i) gravitational phase transitions appear with a distinctive universal feature: a square-root branch point singularity in any space–time dimensions. This is of the type of the de Vega–Sánchez transition for the thermal self-gravitating gas of point particles. (ii) There are no phase transitions in AdS alone. (iii) For dS background, upper bounds of the Hubble constant H are found, dictated by the quantum string phase transition. (iv) The Hawking temperature and the Hagedorn temperature are the same concept but in different (semiclassical and quantum) gravity regimes respectively. (v) The last stage of black hole evaporation is a microscopic string state with a finite string critical temperature which decays as usual quantum strings do in nonthermal pure quantum radiation (no information loss). (vi) New lower string bounds are given for the Kerr–Newman black hole angular momentum and charge, which are entirely different from the upper classical bounds. (vii) Semiclassical gravity states undergo a phase transition into quantum string states of the same system, these states are duals of each other in the precise sense of the usual classical–quantum (wave–particle) duality, which is universal irrespective of any symmetry or isommetry of the space–time and of the number or the kind of space–time dimensions.

43

SANDERS, KO. "THERMAL EQUILIBRIUM STATES OF A LINEAR SCALAR QUANTUM FIELD IN STATIONARY SPACE–TIMES." International Journal of Modern Physics A 28, no. 10 (April 17, 2013): 1330010. http://dx.doi.org/10.1142/s0217751x1330010x.

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The linear scalar quantum field, propagating in a globally hyperbolic space–time, is a relatively simple physical model that allows us to study many aspects in explicit detail. In this review, we focus on the thermal equilibrium (KMS) states of such a field in a stationary space–time. Our presentation draws on several existing sources and aims to give a unified exposition, while weakening certain technical assumptions. In particular we drop all assumptions on the behavior of the time-like Killing field, which is important for physical applications to the exterior region of a stationary black hole. Our review includes results on the existence and uniqueness of ground and KMS states, as well as an evaluation of the evidence supporting the KMS-condition as a characterization of thermal equilibrium. We draw attention to the poorly understood behavior of the temperature of the quantum field with respect to locality. If the space–time is standard static, the analysis can be done more explicitly. For compact Cauchy surfaces we consider Gibbs states and their properties. For general Cauchy surfaces we give a detailed justification of the Wick rotation, including the explicit determination of the Killing time dependence of the quasi-free KMS states.

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ALENCAR, G., I. GUEDES, R. R. LANDIM, and R. N. COSTA FILHO. "AN EXACT SOLUTION TO THE QUANTIZED ELECTROMAGNETIC FIELD IN D-DIMENSIONAL DE SITTER SPACE–TIMES." International Journal of Modern Physics A 27, no. 30 (December 6, 2012): 1250177. http://dx.doi.org/10.1142/s0217751x12501771.

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In this work, we investigate the quantum theory of light propagating in D-dimensional de Sitter space–times. To do so, we use the method of dynamic invariants to obtain the solution of the time-dependent Schrödinger equation. The quantum behavior of the electromagnetic field in this background is analyzed. As the electromagnetism loses its conformality in D≠4, we point out that there will be particle production and comoving objects will feel a Bunch–Davies thermal bath. This may become important in extra dimension physics and raises the intriguing possibility that precise measurements of the Cosmic Microwave Background could verify the existence of extra dimensions.

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Boumali, Abdelmalek, and Houcine Aounallah. "Exact Solutions of Scalar Bosons in the Presence of the Aharonov-Bohm and Coulomb Potentials in the Gravitational Field of Topological Defects." Advances in High Energy Physics 2018 (2018): 1–9. http://dx.doi.org/10.1155/2018/1031763.

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We analyze the relativistic quantum motion of a charged scalar particles in the presence of an Aharonov-Bohm and Coulomb potentials in the space-times produced by an idealized cosmic string and global monopole. We have calculated and discussed the eigensolutions of DKP equation and their dependence on both the geometry of the space-times and coupling constants parameters.

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Giacomini, Flaminia. "Spacetime Quantum Reference Frames and superpositions of proper times." Quantum 5 (July 22, 2021): 508. http://dx.doi.org/10.22331/q-2021-07-22-508.

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In general relativity, the description of spacetime relies on idealised rods and clocks, which identify a reference frame. In any concrete scenario, reference frames are associated to physical systems, which are ultimately quantum in nature. A relativistic description of the laws of physics hence needs to take into account such quantum reference frames (QRFs), through which spacetime can be given an operational meaning. Here, we introduce the notion of a spacetime quantum reference frame, associated to a quantum particle in spacetime. Such formulation has the advantage of treating space and time on equal footing, and of allowing us to describe the dynamical evolution of a set of quantum systems from the perspective of another quantum system, where the parameter in which the rest of the physical systems evolves coincides with the proper time of the particle taken as the QRF. Crucially, the proper times in two different QRFs are not related by a standard transformation, but they might be in a quantum superposition one with respect to the other.Concretely, we consider a system of N relativistic quantum particles in a weak gravitational field, and introduce a timeless formulation in which the global state of the N particles appears "frozen", but the dynamical evolution is recovered in terms of relational quantities. The position and momentum Hilbert space of the particles is used to fix the QRF via a transformation to the local frame of the particle such that the metric is locally inertial at the origin of the QRF. The internal Hilbert space corresponds to the clock space, which keeps the proper time in the local frame of the particle. Thanks to this fully relational construction we show how the remaining particles evolve dynamically in the relational variables from the perspective of the QRF. The construction proposed here includes the Page-Wootters mechanism for non interacting clocks when the external degrees of freedom are neglected. Finally, we find that a quantum superposition of gravitational redshifts and a quantum superposition of special-relativistic time dilations can be observed in the QRF.

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Ioskevich, Alex. "Quantum Propulsion: Background and Practical Applications." European Journal of Applied Physics 6, no. 2 (March 7, 2024): 1–9. http://dx.doi.org/10.24018/ejphysics.2024.6.2.294.

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This is the first introduction of new and revolutionary aerospace engines and propulsion methods. Our organization is currently developing quantum propulsion systems and space vehicles that will be capable of flying with enormous speed (potentially reaching and exceeding the speed of light) and will have unseen-before manoeuvrability and lifting capacity. They will provide 100% crew protection from deadly sun and space radiation which is essential for safe deep space travel and manned space exploration. They will also provide spacecraft with protection against space particles. To date, we have managed to crack the main secret of practical quantum engine design and we are ready to develop it further into fully operational aerospace vehicles. Quantum propulsion systems are the only systems that can facilitate realistic prospects of space mining on the industrial scale and deep space colonisation, including colonisation of habitable planets in the future. The cost efficiency of this new technology is going to be enormous. Development and production costs of quantum aerospace vehicles compared to production costs of chemical fuel jet spacecraft allow to reduce price per kilo space launch ratio hundreds of times, making deep space exploration and commercialisation more accessible and practically feasible at last. Manufacturing and maintenance of quantum-propelled flying machines that can reach the age of our solar system within hours will be no more expensive than manufacturing jet planes or helicopters of the same size. Quantum propulsion systems are going to replace outdated chemical fuel rocket and jet engines in the near future and will become the mainstay of air travel and space exploration.

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Turkeshi, Xhek, and Piotr Sierant. "Hilbert Space Delocalization under Random Unitary Circuits." Entropy 26, no. 6 (May 29, 2024): 471. http://dx.doi.org/10.3390/e26060471.

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The unitary dynamics of a quantum system initialized in a selected basis state yield, generically, a state that is a superposition of all the basis states. This process, associated with the quantum information scrambling and intimately tied to the resource theory of coherence, may be viewed as a gradual delocalization of the system’s state in the Hilbert space. This work analyzes the Hilbert space delocalization under the dynamics of random quantum circuits, which serve as a minimal model of the chaotic dynamics of quantum many-body systems. We employ analytical methods based on the replica trick and Weingarten calculus to investigate the time evolution of the participation entropies which quantify the Hilbert space delocalization. We demonstrate that the participation entropies approach, up to a fixed accuracy, their long-time saturation value in times that scale logarithmically with the system size. Exact numerical simulations and tensor network techniques corroborate our findings.

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Bytsenko, Andrei A., Guido Cognola, Luciano Vanzo, and Sergio Zerbini. "Quantum fields and extended objects in space-times with constant curvature spatial section." Physics Reports 266, no. 1-2 (February 1996): 1–126. http://dx.doi.org/10.1016/0370-1573(95)00053-4.

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Gottschalk, Hanno, and Horst Thaler. "An Indefinite Metric Model for Interacting Quantum Fields on Globally Hyperbolic Space-Times." Annales Henri Poincaré 4, no. 4 (August 2003): 637–59. http://dx.doi.org/10.1007/s00023-003-0142-8.

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