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Статті в журналах з теми "Cosmological phase transition"

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Автор: Grafiati

Опубліковано: 14 березня 2023

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1

KIM, SANG PYO. "DYNAMICAL THEORY OF PHASE TRANSITIONS AND COSMOLOGICAL EW AND QCD PHASE TRANSITIONS." Modern Physics Letters A 23, no. 17n20 (June 28, 2008): 1325–35. http://dx.doi.org/10.1142/s0217732308027692.

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We critically review the cosmological EW and QCD phase transitions. The EW and QCD phase transitions would have proceeded dynamically since the expansion of the universe determines the quench rate and critical behaviors at the onset of phase transition slow down the phase transition. We introduce a real-time quench model for dynamical phase transitions and describe the evolution using a canonical real-time formalism. We find the correlation function, the correlation length and time and then discuss the cosmological implications of dynamical phase transitions on EW and QCD phase transitions in the early universe.

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2

Athron, Peter, Csaba Balázs, and Lachlan Morris. "Supercool subtleties of cosmological phase transitions." Journal of Cosmology and Astroparticle Physics 2023, no. 03 (March 1, 2023): 006. http://dx.doi.org/10.1088/1475-7516/2023/03/006.

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Abstract We investigate rarely explored details of supercooled cosmological first-order phase transitions at the electroweak scale, which may lead to strong gravitational wave signals or explain the cosmic baryon asymmetry. The nucleation temperature is often used in phase transition analyses, and is defined through the nucleation condition: on average one bubble has nucleated per Hubble volume. We argue that the nucleation temperature is neither a fundamental nor essential quantity in phase transition analysis. We illustrate scenarios where a transition can complete without satisfying the nucleation condition, and conversely where the nucleation condition is satisfied but the transition does not complete. We also find that simple nucleation heuristics, which are defined to approximate the nucleation temperature, break down for strong supercooling. Thus, studies that rely on the nucleation temperature — approximated or otherwise — may misclassify the completion of a transition. Further, we find that the nucleation temperature decouples from the progress of the transition for strong supercooling. We advocate use of the percolation temperature as a reference temperature for gravitational wave production, because the percolation temperature is directly connected to transition progress and the collision of bubbles. Finally, we provide model-independent bounds on the bubble wall velocity that allow one to predict whether a transition completes based only on knowledge of the bounce action curve. We apply our methods to find empirical bounds on the bubble wall velocity for which the physical volume of the false vacuum decreases during the transition. We verify the accuracy of our predictions using benchmarks from a high temperature expansion of the Standard Model and from the real scalar singlet model.

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3

Boeckel, Tillmann, Simon Schettler, and Jürgen Schaffner-Bielich. "The cosmological QCD phase transition revisited." Progress in Particle and Nuclear Physics 66, no. 2 (April 2011): 266–70. http://dx.doi.org/10.1016/j.ppnp.2011.01.017.

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4

HWANG, W.-Y. P. "SOME THOUGHTS ON THE COSMOLOGICAL QCD PHASE TRANSITION." International Journal of Modern Physics A 23, no. 30 (December 10, 2008): 4757–77. http://dx.doi.org/10.1142/s0217751x08042845.

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Анотація:

The cosmological QCD phase transitions may have taken place between 10-5 s and 10-4 s in the early universe offers us one of the most intriguing and fascinating questions in cosmology. In bag models, the phase transition is described by the first-order phase transition and the role played by the latent "heat" or energy released in the transition is highly nontrivial and is being classified as the first-order phase transition. In this presentation, we assume, first of all, that the cosmological QCD phase transition, which happened at a time between 10-5 s and 10-4 s or at the temperature of about 150 MeV and accounts for confinement of quarks and gluons to within hadrons, would be of first-order. Of course, we may assume that the cosmological QCD phase transition may not be of the first-order. To get the essence out of the first-order scenario, it is sufficient to approximate the true QCD vacuum as one of possibly degenerate vacua and when necessary we try to model it effectively via a complex scalar field with spontaneous symmetry breaking. On the other hand, we may use a real scalar field in describing the non-first-order QCD phase transition. In the first-order QCD phase transition, we could examine how and when "pasted" or "patched" domain walls are formed, how long such walls evolve in the long run, and we believe that the significant portion of dark matter could be accounted for in terms of such domain-wall structure and its remnants. Of course, the cosmological QCD phase transition happened in the way such that the false vacua associated with baryons and many other color-singlet objects did not disappear (that is, using the bag-model language, there are bags of radius 1.0 fermi for the baryons) — but the amount of the energy remained in the false vacua is negligible by comparison. The latent energy released due to the conversion of the false vacua to the true vacua, in the form of "pasted" or "patched" domain walls in the short run and their numerous evolved objects, should make the concept of the "radiation-dominated" epoch, or of the "matter-dominated" epoch to be reexamined.

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5

HWANG, W.-Y. P. "DARK MATTER AND COSMOLOGICAL QCD PHASE TRANSITION." Modern Physics Letters A 22, no. 25n28 (September 14, 2007): 1971–85. http://dx.doi.org/10.1142/s0217732307025200.

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Анотація:

In this talk, we take the wisdom that the cosmological QCD phase transition, which happened at a time between 10−5 sec and 10−4 sec or at the temperature of about 150 MeV and accounts for confinement of quarks and gluons to within hadrons, would be of first order, i.e., would release latent "heat" or latent energy. I wish to base on two important points, i.e. (1) that we have 25% dark matter in the present Universe, and (2) that when the early universe underwent the cosmological QCD phase transition it released 1.02 × 10gm/cm3 in latent energy huge compared to 5.88 × 109 gm/cm3 radiation (photon) energy, to deduce that the two numbers are in fact closely related. It is sufficient to approximate the true QCD vacuum as one of degenerate θ-vacua and can be modelled effectively via a complex scalar field with spontaneous symmetry breaking. We examine how "pasted" or "patched" domain walls are formed, how such walls evolve in the long run, and we believe that the majority of dark matter could be accounted for in terms of such domain-wall structure and its remnants. The latent energy released due to the conversion of the false vacua to the true vacua, in the form of "pasted" or "patched" domain walls at first and their evolved objects, make it obsolete the "radiation-dominated" epoch or later on the "matter-dominated" epoch.

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6

Morikawa, M. "Cosmological Inflation as a Quantum Phase Transition." Progress of Theoretical Physics 93, no. 4 (April 1, 1995): 685–709. http://dx.doi.org/10.1143/ptp/93.4.685.

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7

Matsuda, Tomohiro. "Cosmological perturbations from an inhomogeneous phase transition." Classical and Quantum Gravity 26, no. 14 (June 26, 2009): 145011. http://dx.doi.org/10.1088/0264-9381/26/14/145011.

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8

Bhattacharyya, Abhijit, Jan-e. Alam, Sourav Sarkar, Pradip Roy, Bikash Sinha, Sibaji Raha, and Pijushpani Bhattacharjee. "Cosmological QCD phase transition and dark matter." Nuclear Physics A 661, no. 1-4 (December 1999): 629–32. http://dx.doi.org/10.1016/s0375-9474(99)85104-5.

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9

Bödeker, D., W. Buchmüller, Z. Fodor, and T. Helbig. "Aspects of the cosmological electroweak phase transition." Nuclear Physics B 423, no. 1 (July 1994): 171–96. http://dx.doi.org/10.1016/0550-3213(94)90569-x.

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10

Jinno, Ryusuke, Thomas Konstandin, Henrique Rubira, and Isak Stomberg. "Higgsless simulations of cosmological phase transitions and gravitational waves." Journal of Cosmology and Astroparticle Physics 2023, no. 02 (February 1, 2023): 011. http://dx.doi.org/10.1088/1475-7516/2023/02/011.

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Abstract First-order cosmological phase transitions in the early Universe source sound waves and, subsequently, a background of stochastic gravitational waves. Currently, predictions of these gravitational waves rely heavily on simulations of a Higgs field coupled to the plasma of the early Universe, the former providing the latent heat of the phase transition. Numerically, this is a rather demanding task since several length scales enter the dynamics. From smallest to largest, these are the thickness of the Higgs interface separating the different phases, the shell thickness of the sound waves, and the average bubble size. In this work, we present an approach to perform Higgsless simulations in three dimensions, producing fully nonlinear results, while at the same time removing the hierarchically smallest scale from the lattice. This significantly reduces the complexity of the problem and contributes to making our approach highly efficient. We provide spectra for the produced gravitational waves for various choices of wall velocity and strength of the phase transition, as well as introduce a fitting function for the spectral shape.

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11

MÉGEVAND, ARIEL. "GRAVITATIONAL WAVES FROM COSMOLOGICAL PHASE TRANSITIONS." International Journal of Modern Physics A 24, no. 08n09 (April 10, 2009): 1541–44. http://dx.doi.org/10.1142/s0217751x09044966.

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12

KAJANTIE, K. "INTERFACES AND THE QUARK HADRON PHASE TRANSITION." International Journal of Modern Physics C 03, no. 05 (October 1992): 921–29. http://dx.doi.org/10.1142/s0129183192000580.

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Анотація:

The tension of the interface between the high and low temperature phases of finite temperature Quantum Chromodynamics is an important characteristic of the quarkhadron phase transition. We discuss its cosmological effects and its determination, for planar and spherical interfaces, with lattice Monte Carlo techniques for the case of pure glue, Nt=2 SU(3) gauge theory.

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13

Cho, Y. M. "Cosmological Implication of Electroweak Monopole." EPJ Web of Conferences 182 (2018): 02030. http://dx.doi.org/10.1051/epjconf/201818202030.

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Анотація:

We estimate the remnant electroweak monopole density of the standard model in the present universe. We show that, although the electroweak phase transition is of the first order, the monopole production comes from the thermal fluctuations of the Higgs field after the phase transition, not the vacuum bubble collisions during the phase transition. Moreover, most of the monopoles produced initially are annihilated as soon as created, and this annihilation continues very long time, longer than the muon pair annihilation time. As the result the remnant monopole density at present universe becomes very small, of 10-11 of the critical density, too small to be the dark matter. We discuss the physical implications of our results on the ongoing monopole detection experiments.

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14

Cho, Y. M. "Cosmological Implications of Electroweak Monopole." EPJ Web of Conferences 168 (2018): 01002. http://dx.doi.org/10.1051/epjconf/201816801002.

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Анотація:

In this talk we review the basic features of the electroweak monopole, and estimate the remnant electroweak monopole density of the standard model in the present universe. We show that, although the electroweak phase transition is of the first order, the monopole production comes from the thermal fluctuations of the Higgs field after the phase transition, not the vacuum bubble collisions during the phase transition. Moreover, most of the monopoles produced initially are annihilated as soon as created, and this annihilation continues very long time, longer than the muon pair annihilation time. As the result the remnant monopole density at present universe becomes very small, of 10-11 of the critical density, too small to be the dark matter. We discuss the physical implications of our results on the ongoing monopole detection experiments.

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15

LIKO, TOMÁŠ, and PAUL S. WESSON. "THE BIG BANG AS A PHASE TRANSITION." International Journal of Modern Physics A 20, no. 10 (April 20, 2005): 2037–45. http://dx.doi.org/10.1142/s0217751x05022299.

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We study a five-dimensional cosmological model, which suggests that the universe began as a discontinuity in a scalar (Higgs-type) field, or alternatively as a conventional four-dimensional phase transition.

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16

Hwang, W.-Y. P. "What Happened to the Cosmological QCD Phase Transition?" Journal of the Korean Physical Society 53, no. 9(2) (August 14, 2008): 1115–25. http://dx.doi.org/10.3938/jkps.53.1115.

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17

Nishimura, H., and Y. Hayashi. "Preon model and cosmological quantum-hyperchromodynamic phase transition." Physical Review D 35, no. 10 (May 15, 1987): 3151–57. http://dx.doi.org/10.1103/physrevd.35.3151.

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18

Alcock, C., G. M. Fuller, G. J. Mathews, and B. Meyer. "Cosmological consequences of the quark-hadron phase transition." Nuclear Physics A 498 (July 1989): 301–12. http://dx.doi.org/10.1016/0375-9474(89)90607-6.

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19

Nagasawa, M., and J. Yokoyama. "Reduction of Sound Speed during Cosmological First Order Phase Transition." Symposium - International Astronomical Union 183 (1999): 313. http://dx.doi.org/10.1017/s0074180900133042.

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Анотація:

The degree of sound speed reduction is estimated during the coexistence epoch of quark-gluon and hadron phases in the first-order QCD phase transition[1]. The sound speed in a mixture is obtained by simply replacing the energy density with the mean value in the usual formula[2]. Since the adiabatic condition is nothing but the second law of thermodynamics which is useless for the purpose of calculating the sound speed qualitatively, we adopt the conservation of the quality which is the energy fraction of the high-energy phase[2]. This is appropriate because the transition of the phases through bubble nucleation is totally suppressed at the coexistence temperature and the expansion speed of bubbles is so small that energy transfer through bubble expansion or contraction is also expected to be negligible during sound-wave propagation. Using the bag model, the numerical value of the minimum sound speed can be calculated as where the uncertainty comes from the selection of the number of relativistic quark species. Thus we can say that the quark-hadron phase transition has no drastic effect on the development of cosmological density perturbations.

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20

DE RISI, G. "COSMOLOGICAL BACKREACTION OF HEAVY STRING STATES." Modern Physics Letters A 26, no. 35 (November 20, 2011): 2615–26. http://dx.doi.org/10.1142/s0217732311036991.

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We propose a mechanism to have a smooth transition from a pre-Big Bang phase to a standard cosmological phase. Such transition is driven by gravitational production of heavy massive string states that backreact on the geometry to stop the growth of the curvature. Close to the string scale, particle creation can become effective because the string phase space compensate the exponential suppression of the particle production. Numerical solutions for the evolution of the Universe with this source are presented.

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21

KIM, WONTAE, and EDWIN J. SON. "TWO NONCOMMUTATIVE PARAMETERS AND REGULAR COSMOLOGICAL PHASE TRANSITION IN THE SEMICLASSICAL DILATON COSMOLOGY." Modern Physics Letters A 23, no. 15 (May 20, 2008): 1079–91. http://dx.doi.org/10.1142/s0217732308027047.

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We study cosmological phase transitions from modified equations of motion by introducing two noncommutative parameters in the Poisson brackets, which describes the initial- and future-singularity-free phase transition in the soluble semiclassical dilaton gravity with a nonvanishing cosmological constant. Accelerated expansion and decelerated expansion appear alternatively, where the model contains the second accelerated expansion. The final stage of the universe approaches the flat spacetime independent of the initial state of the curvature scalar as long as the product of the two noncommutative parameters is less than one. Finally, we show that the initial-singularity-free condition is related to the second accelerated expansion of the universe.

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22

Lev, B. I., and A. G. Zagorodny. "Some peculiarities of noise-induced phase transition." Low Temperature Physics 48, no. 11 (November 2022): 949–55. http://dx.doi.org/10.1063/10.0014595.

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Анотація:

Two fundamental evolutionary principles, namely the H-theorem and the least-energy principle, are applied to describe the phase transition in condensed environments and cosmological models. We assume that in the presence of a spontaneously induced scalar field, which can be treated as an order parameter, the energy of the ground state is lower than the ground state energy without such a field. Taking into account the self-consistent interaction of the scalar field with the fluctuations of the fields of other nature and the principles mentioned above, it is possible to show the possibility of the phase transition and to find the conditions for such transition in terms of fluctuation characteristics and coupling parameter. These principles are employed to reveal probable phase transitions in condensed matter physics and cosmology.

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23

Mielczarek, Jakub. "Big Bang as a Critical Point." Advances in High Energy Physics 2017 (2017): 1–5. http://dx.doi.org/10.1155/2017/4015145.

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This article addresses the issue of possible gravitational phase transitions in the early universe. We suggest that a second-order phase transition observed in the Causal Dynamical Triangulations approach to quantum gravity may have a cosmological relevance. The phase transition interpolates between a nongeometric crumpled phase of gravity and an extended phase with classical properties. Transition of this kind has been postulated earlier in the context of geometrogenesis in the Quantum Graphity approach to quantum gravity. We show that critical behavior may also be associated with a signature change in Loop Quantum Cosmology, which occurs as a result of quantum deformation of the hypersurface deformation algebra. In the considered cases, classical space-time originates at the critical point associated with a second-order phase transition. Relation between the gravitational phase transitions and the corresponding change of symmetry is underlined.

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24

GUENDELMAN, E. I., and A. B. KAGANOVICH. "DILATON INDUCED QUANTUM INFLATION-COMPACTIFICATION AND POSSIBILITY OF TRANSITION TO CLASSICAL ERA." Modern Physics Letters A 09, no. 13 (April 30, 1994): 1141–50. http://dx.doi.org/10.1142/s0217732394000952.

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In many interesting models, including superstring theories, a vacuum with negative cosmological constant is predicted. For quantum cosmology (in higher dimensions) in the presence of coherent dilaton excitations and a negative cosmological constant, the role of cosmic time can be understood and we can then predict the existence of a “quantum inflationary phase” for some dimensions and a simultaneous “quantum deflationary phase” for the remaining dimensions. We discuss qualitatively how it may be possible to exit from this inflation-compactification era and give an example which involves a transition to a phase with zero cosmological constant which allows a classical description at late times.

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25

Borghini, N., W. N. Cottingham, and R. Vinh Mau. "Possible cosmological implications of the quark-hadron phase transition." Journal of Physics G: Nuclear and Particle Physics 26, no. 6 (May 8, 2000): 771–85. http://dx.doi.org/10.1088/0954-3899/26/6/302.

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26

Quashnock, Jean M., Abraham Loeb, and David N. Spergel. "Magnetic field generation during the cosmological QCD phase transition." Astrophysical Journal 344 (September 1989): L49. http://dx.doi.org/10.1086/185528.

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27

Huang, Wung-Hong. "Finite-temperature cosmological phase transition in a rotating spacetime." Classical and Quantum Gravity 8, no. 8 (August 1, 1991): 1471–79. http://dx.doi.org/10.1088/0264-9381/8/8/012.

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28

Kurki-Suonio, H., and M. Laine. "Real-Time History of the Cosmological Electroweak Phase Transition." Physical Review Letters 77, no. 19 (November 4, 1996): 3951–54. http://dx.doi.org/10.1103/physrevlett.77.3951.

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29

Kahniashvili, Tina, Alexander G. Tevzadze, and Bharat Ratra. "PHASE TRANSITION GENERATED COSMOLOGICAL MAGNETIC FIELD AT LARGE SCALES." Astrophysical Journal 726, no. 2 (December 16, 2010): 78. http://dx.doi.org/10.1088/0004-637x/726/2/78.

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30

McDonald, John. "Dynamical cosmological constant from a very recent phase transition." Physics Letters B 498, no. 3-4 (January 2001): 263–71. http://dx.doi.org/10.1016/s0370-2693(00)01389-7.

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31

Son, Edwin J., and Wontae Kim. "Smooth cosmological phase transition in the Hořava-Lifshitz gravity." Journal of Cosmology and Astroparticle Physics 2010, no. 06 (June 24, 2010): 025. http://dx.doi.org/10.1088/1475-7516/2010/06/025.

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32

Akdeniz, K. G., A. Hacinliyan, and J. Kalayci. "Phase transition in conformal gravity with cosmological time background." Physics Letters B 158, no. 1 (August 1985): 28–30. http://dx.doi.org/10.1016/0370-2693(85)90732-4.

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33

Midorikawa, Shoichi. "Bubble collisions in the cosmological quark-hadron phase transition." Physics Letters B 158, no. 2 (August 1985): 107–9. http://dx.doi.org/10.1016/0370-2693(85)91373-5.

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34

Ma, Meng-Sen, Hui-Hua Zhao, Li-Chun Zhang, and Ren Zhao. "Existence condition and phase transition of Reissner–Nordström–de Sitter black hole." International Journal of Modern Physics A 29, no. 09 (April 8, 2014): 1450050. http://dx.doi.org/10.1142/s0217751x1450050x.

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Анотація:

After introducing the connection between the black hole horizon and the cosmological horizon, we discuss the thermodynamic properties of Reissner–Nordström–de Sitter (RN–dS) space–time. We present the condition under which RN–dS black hole can exist. Employing Ehrenfest' classification, we conclude that the phase transition of RN–dS black hole is the second-order one. The position of the phase transition point is irrelevant to the electric charge of the system. It only depends on the ratio of the black hole horizon and the cosmological horizon.

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35

Zou, De-Cheng, Ming Zhang, Chao Wu, and Rui-Hong Yue. "Critical Phenomena of Charged AdS Black Holes in Rastall Gravity." Advances in High Energy Physics 2020 (January 24, 2020): 1–9. http://dx.doi.org/10.1155/2020/4065254.

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Анотація:

We construct analytical charged anti-de Sitter (AdS) black holes surrounded by perfect fluids in four dimensional Rastall gravity. Then, we discuss the thermodynamics and phase transitions of charged AdS black holes immersed in regular matter like dust and radiation, or exotic matter like quintessence, ΛCDM type, and phantom fields. Surrounded by phantom field, the charged AdS black hole demonstrates a new phenomenon of reentrant phase transition (RPT) when the parameters Q, Np, and ψ satisfy some certain condition, along with the usual small/large black hole (SBH/LBH) phase transition for the surrounding dust, radiation, quintessence, and cosmological constant fields.

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36

Capozziello, Salvatore, Peter K. S. Dunsby, and Orlando Luongo. "Model-independent reconstruction of cosmological accelerated–decelerated phase." Monthly Notices of the Royal Astronomical Society 509, no. 4 (November 8, 2021): 5399–415. http://dx.doi.org/10.1093/mnras/stab3187.

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ABSTRACT We propose two model-independent methods to obtain constraints on the transition and equivalence redshifts, ztr and zeq, respectively. In particular, we consider ztr as the onset of cosmic acceleration, whereas zeq the redshift at which the densities of dark energy and pressureless matter are equated. With this prescription, we expand the Hubble and deceleration parameters up to two hierarchical orders and show a linear correlation between transition and equivalence, from which we propose exclusion plots where zeq is not allowed to span. To this end, we discuss how to build up cosmographic expansions in terms of ztr and compute the corresponding observable quantities by directly fitting the luminosity and angular distances and the Hubble rate with cosmic data. We make our computations through Monte Carlo fits involving Type Ia supernova, baryonic acoustic oscillation, and Hubble most recent data catalogues. We show that at 1σ confidence level the Lambda cold dark matter predictions on ztr and zeq are slightly confirmed, although at 2σ confidence level dark energy expectations cannot be excluded. Finally, we theoretically interpret our outcomes and discuss possible limitations of our overall approach.

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37

Zhang, Yang, Yu-bo Ma, Yun-zhi Du, Huai-fan Li, and Li-chun Zhang. "Phase Transition and Entropic Force in Reissner-Nordström-de Sitter Spacetime." Advances in High Energy Physics 2022 (October 13, 2022): 1–9. http://dx.doi.org/10.1155/2022/7376502.

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Анотація:

In this paper, thermodynamic properties of the Reissner-Nordström-de Sitter (RN-dS) black hole have been studied on the basis of the correlation between the black hole and cosmological horizons. It is found that the RN-dS black hole experiences a phase transition, when its state parameters satisfy certain conditions. From the analysis of the interaction between two horizons in RN-dS spacetime, we get the numerical solution of the interaction between two horizons. It makes us to realize the force between the black hole and cosmological horizons, which can be regarded as a candidate to explain our accelerating expansion universe. That provides a new window to explore the physical mechanism of the cosmic accelerating expansion.

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38

AbdusSalam, Shehu, Mohammad Javad Kazemi, and Layla Kalhor. "Upper limit on first-order electroweak phase transition strength." International Journal of Modern Physics A 36, no. 05 (February 20, 2021): 2150024. http://dx.doi.org/10.1142/s0217751x2150024x.

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For a cosmological first-order electroweak phase transition, requiring no sphaleron washout of baryon number violating processes leads to a lower bound on the strength of the transition. The velocity of the boundary between the phases, the so-called bubble wall, can become ultrarelativistic if the friction due to the plasma of particles is not sufficient to retard the wall’s acceleration. This bubble “runaway” should not occur if a successful baryon asymmetry generation due to the transition is required. Using Boedeker–Moore criterion for bubble wall runaway, within the context of an extension of the Standard Model of particle physics with a real gauge-single scalar field, we show that a nonrunaway transition requirement puts an upper bound on the strength of the first-order phase transition.

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39

Lerambert-Potin, Pauline, and José Antonio de Freitas Pacheco. "Gravitational Waves from the Cosmological Quark-Hadron Phase Transition Revisited." Universe 7, no. 8 (August 16, 2021): 304. http://dx.doi.org/10.3390/universe7080304.

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The recent claim by the NANOGrav collaboration of a possible detection of an isotropic gravitational wave background stimulated a series of investigations searching for the origin of such a signal. The QCD phase transition appears as a natural candidate and in this paper the gravitational spectrum generated during the conversion of quarks into hadrons is calculated. Here, contrary to recent studies, equations of state for the quark-gluon plasma issued from the lattice approach were adopted. The duration of the transition, an important parameter affecting the amplitude of the gravitational wave spectrum, was estimated self-consistently with the dynamics of the universe controlled by the Einstein equations. The gravitational signal generated during the transition peaks around 0.28 μHz with amplitude of h02Ωgw≈7.6×10−11, being unable to explain the claimed NANOGrav signal. However, the expected QCD gravitational wave background could be detected by the planned spatial interferometer Big Bang Observer in its advanced version for frequencies above 1.0 mHz. This possible detection assumes that algorithms recently proposed will be able to disentangle the cosmological signal from that expected for the astrophysical background generated by black hole binaries.

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40

Mégevand, Ariel, and Alejandro D. Sánchez. "Analytic approach to the motion of cosmological phase transition fronts." Nuclear Physics B 865, no. 2 (December 2012): 217–37. http://dx.doi.org/10.1016/j.nuclphysb.2012.08.001.

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41

Huang, Wung-Hong. "Quantum field effects on cosmological phase transition in anisotropic spacetimes." Classical and Quantum Gravity 10, no. 10 (October 1, 1993): 2021–33. http://dx.doi.org/10.1088/0264-9381/10/10/009.

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42

Lindesay, James. "Consequences of a Cosmological Phase Transition at the TeV Scale." Foundations of Physics 37, no. 4-5 (March 13, 2007): 491–531. http://dx.doi.org/10.1007/s10701-007-9115-y.

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43

GHANEH, T., F. DARABI, and H. MOTAVALLI. "SIGNATURE CHANGE BY GUP." International Journal of Modern Physics D 22, no. 05 (April 2013): 1350026. http://dx.doi.org/10.1142/s0218271813500260.

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We revisit the issue of continuous signature transition from Euclidean to Lorentzian metrics in a cosmological model described by Friedmann–Robertson–Walker (FRW) metric minimally coupled with a self-interacting massive scalar field. Then, using a noncommutative (NC) phase space of dynamical variables deformed by generalized uncertainty principle (GUP), we show that the signature transition occurs even for a model described by the FRW metric minimally coupled with a free massless scalar field accompanied by a cosmological constant. This indicates that the continuous signature transition might have been easily occurred at early universe just by a free massless scalar field, a cosmological constant and a NC phase space deformed by GUP, without resorting to a massive scalar field having an ad hoc complicate potential. We also study the quantum cosmology of the model and obtain a solution of Wheeler–DeWitt (WD) equation which shows a good correspondence with the classical path.

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44

Ghasemi, Elham, and Hossein Ghaffarnejad. "Thermodynamic Phase Transition of Generalized Ayon-Beato Garcia Black Holes." Advances in High Energy Physics 2023 (January 24, 2023): 1–9. http://dx.doi.org/10.1155/2023/6446767.

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In this work, we study thermodynamics of generalized Ayon-Beato and Garcia (ABG) black hole metric which contains three parameters named as mass m , magnetic charge q , and dimensionless coupling constant of nonlinear electrodynamics interacting field γ . We showed that central regions of this black hole behaves as dS (AdS) vacuum space by setting q < 2 m q > 2 m and in the case q = 2 m reaches to a flat Minkowski space. In the large distances, this black hole behaves as a Reissner-Nordstrom BH. However, an important role of the charge q appeared in the production of a formal variable cosmological parameter which will support pressure coordinate in the thermodynamic perspective of this black hole in our setup. We should point that this formal variable cosmological parameter is different with cosmological constant which comes from AdS/CFT correspondence, and it is effective at large distances as AdS space pressure. In our setup, the assumed pressure originated from the internal material of the black hole say q and m here. By calculating the Hawking temperature of this black hole, we obtain equation of state. Then, we plotted isothermal P-V curves and heat capacity at constant pressure. They show that the system participates in the small to large phase transition of the black hole or the Hawking-Page phase transition which is similar to the van der Waals phase transition in the ordinary thermodynamics systems. In fact in the Hawking-Page phase transition disequilibrium, evaporating generalized ABG black hole reaches to a vacuum AdS space finally.

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45

Zaripov, Farkhat. "Oscillating Cosmological Solutions in the Modified Theory of Induced Gravity." Advances in Astronomy 2019 (April 24, 2019): 1–15. http://dx.doi.org/10.1155/2019/1502453.

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This work is the extension of author’s research, where the modified theory of induced gravity (MTIG) is proposed. In the framework of the MTIG, the mechanism of phase transitions and the description of multiphase behavior of the cosmological scenario are proposed. The theory describes two systems (stages): Einstein (ES) and “restructuring” (RS). This process resembles the phenomenon of a phase transition, where different phases (Einstein’s gravitational systems, but with different constants) pass into each other. The hypothesis that such transitions are random and lead to stochastic behavior of cosmological parameters is considered. In our model, effective gravitational and cosmological “constants” arise, which are defined by the “mean square” of the scalar fields. These parameters can be compared with observations related to the phenomenon of dark energy. The aim of the work is to solve equations of MTIG for the case of a quadratic potential and compare them with observational cosmology data. The interaction of fundamental scalar fields and matter in the form of an ideal fluid is introduced and investigated. For the case of Friedmann-Robertson-Walker space-time, numerical solutions of nonlinear MTIG equations are obtained using the qualitative theory of dynamical systems and mathematical computer programs. For the case of a linear potential, examples joining of solutions, the ES and RS stages, of the evolution of the cosmological model are given. It is shown that the values of such parameters as “Hubble parameter” and gravitational and cosmological “constants” in the RS stage contain solutions oscillating near monotonically developing averages or have stochastic behavior due to random transitions to different stages (RS or ES). Such a stochastic behavior might be at the origin of the tension between CMB measurements of the value of the Hubble parameter today and its local measurements.

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46

AGISHTEIN, M. E., and A. A. MIGDAL. "SIMULATIONS OF FOUR-DIMENSIONAL SIMPLICIAL QUANTUM GRAVITY AS DYNAMICAL TRIANGULATION." Modern Physics Letters A 07, no. 12 (April 20, 1992): 1039–61. http://dx.doi.org/10.1142/s0217732392000938.

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Four-Dimensional Simplicial Quantum Gravity is simulated using the dynamical triangulation approach. We studied simplicial manifolds of spherical topology and found the critical line for the cosmological constant as a function of the gravitational one, separating the phases of opened and closed Universe. When the bare cosmological constant approaches this line from above, the four-volume grows: we reached about 5×104 simplexes, which proved to be sufficient for the statistical limit of infinite volume. However, for the genuine continuum theory of gravity, the parameters of the lattice model should be further adjusted to reach the second order phase transition point, where the correlation length grows to infinity. We varied the gravitational constant, and we found the first order phase transition, similar to the one found in three-dimensional model, except in 4D the fluctuations are rather large at the transition point, so that this is close to the second order phase transition. The average curvature in cutoff units is large and positive in one phase (gravity), and small negative in another (antigravity). We studied the fractal geometry of both phases, using the heavy particle propagator to define the geodesic map, as well as with the old approach using the shortest lattice paths. The heavy propagator geodesic appeared to be much smoother, so that the scaling laws were found, corresponding to finite fractal dimensions: D+~2.3 in the gravity phase and D−~4.6 in the antigravity phase. Similar, but somewhat lower numbers were obtained from the heat kernel singularity. The influence of the αR2 terms in 2, 3 and 4 dimensions is discussed.

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47

Bhardwaj, Vinod Kumar, and Anil Kumar Yadav. "Some Bianchi type-V accelerating cosmological models in f(R,T) = f1(R) + f2(T) formalism." International Journal of Geometric Methods in Modern Physics 17, no. 10 (August 28, 2020): 2050159. http://dx.doi.org/10.1142/s0219887820501595.

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In this paper, we have studied the transition and physical behavior of Bianchi type-V cosmological models within the formalism of [Formula: see text] gravity. To obtain the solution of field equations and phase transition of universe consistent with recent cosmological observations, time varying deceleration parameters are considered. In this paper, we used two different scale factors of the form (i) [Formula: see text], where [Formula: see text] are constants. Here, for [Formula: see text] the universe shows transition with accelerated expansion. (ii) [Formula: see text], where [Formula: see text] and [Formula: see text] are constants. For [Formula: see text], the universe achieves a phase transition from early decelerating to current accelerating phase. The model I initially starts with quintessence scenario ([Formula: see text]) and ends up with ([Formula: see text]) as a model with cosmological constant ([Formula: see text]) as [Formula: see text]. Model II, for [Formula: see text] indicates the phantom energy scenario and for [Formula: see text], the model starts with quintessence [Formula: see text] and ends with vacuum energy scenario. A point type singularity has been observed in the derived model I. Some physical and geometrical properties of the models have been established and discussed to derive the validity of models with respect to recent astrophysical observations.

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48

Wilczek, Frank. "REMARKS ON THE PHASE TRANSITION IN QCD." International Journal of Modern Physics D 03, supp01 (January 1994): 63–79. http://dx.doi.org/10.1142/s0218271894000964.

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The significance of the question of the order of the phase transition in QCD, and recent evidence that real-world QCD is probably close to having a single second order transition as a function of temperature, is reviewed. Although this circumstance seems to remove the possibility that the QCD transition during the big bang might have had spectacular cosmological consequences, there is some good news: it allows highly non-trivial yet reliable quantitative predictions to be made for the behavior near the transition. These predictions can be tested in numerical simulations and perhaps even eventually in heavy ion collisions. The present paper is a very elementary discussion of the relevant concepts, meant to be an accessible introduction for those innocent of the renormalization group approach to critical phenomena and/or the details of QCD.

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49

Patra, B. K., and C. P. Singh. "Baryon contrast ratio in an isentropic cosmological quark-hadron phase transition." Physics Letters B 427, no. 3-4 (May 1998): 241–47. http://dx.doi.org/10.1016/s0370-2693(98)00310-4.

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50

Iso, Ken-ichi, Hideo Kodama, and Katsuhiko Sato. "Cosmological quark-hadron phase transition and formation of isothermal density fluctuations." Physics Letters B 169, no. 4 (April 1986): 337–42. http://dx.doi.org/10.1016/0370-2693(86)90368-0.

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