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Journal articles on the topic 'Cosmological reheating'

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Author: Grafiati

Published: 11 March 2023

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1

Hamazaki, T., and H. Kodama. "Evolution of Cosmological Perturbations during Reheating." Progress of Theoretical Physics 96, no. 6 (December 1, 1996): 1123–45. http://dx.doi.org/10.1143/ptp.96.1123.

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2

XUE, SHE-SHENG. "GRAVITATIONAL INSTANTON AND COSMOLOGICAL TERM." International Journal of Modern Physics A 24, no. 20n21 (August 20, 2009): 3865–91. http://dx.doi.org/10.1142/s0217751x09045844.

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Quantum fluctuation of unstable modes about gravitational instantons causes the instability of flat space at finite temperature, leading to the spontaneous process of nucleating quantum black holes. The energy-density of quantum black holes, depending on the initial temperature, gives the cosmological term, which naturally accounts for the inflationary phase of the early universe. The reheating phase is attributed to the Hawking radiation and annihilation of these quantum black holes. Then, the radiation energy-density dominates over the energy-density of quantum black holes, the universe started the standard cosmology phase. In this phase the energy-density of quantum black holes depends on the reheating temperature. It asymptotically approaches to the cosmological constant in matter domination phase, consistently with current observations.

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3

Martens, Paul, Shinji Mukohyama, and Ryo Namba. "Reheating after relaxation of large cosmological constant." Journal of Cosmology and Astroparticle Physics 2022, no. 11 (November 1, 2022): 047. http://dx.doi.org/10.1088/1475-7516/2022/11/047.

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Abstract We present a cosmological model of an early-time scenario that incorporates a relaxation process of the would-be large vacuum energy, followed by a reheating era connecting to the standard hot big bang universe. Avoiding fine-tuning the cosmological constant is achieved by the dynamics of a scalar field whose kinetic term is modulated by an inverse power of spacetime curvature [1,2]. While it is at work against radiative corrections to the dark energy, this mechanism alone would wipe out not only the vacuum energy but also all other matter contents. Our present work aims to complete the scenario by exploiting a null-energy-condition violating sector whose energy is eventually transferred to a reheating sector. We provide an explicit example of this process and thus a concrete scenario of the cosmic onset that realizes the thermal history of the Universe with a negligible cosmological constant.

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4

Cheong, Dhong Yeon, Sung Mook Lee, and Seong Chan Park. "Reheating in models with non-minimal coupling in metric and Palatini formalisms." Journal of Cosmology and Astroparticle Physics 2022, no. 02 (February 1, 2022): 029. http://dx.doi.org/10.1088/1475-7516/2022/02/029.

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Abstract We study reheating of inflationary models with general non-minimal coupling K(ϕ)R with K(ϕ) ∼ √(V(ϕ)) where R is the Ricci scalar and R is the inflaton potential. In particular, when we take the monomial potential K(ϕ) ∝ ϕ m with m∈ℤ+, we provide general analytic expressions for cosmological observables. We consider a wide range of non-minimal coupling ξ∈[0,∞) in metric and Palatini formalisms and derive the predictions for cosmological observables and the reheating temperature taking a general equation of state parameter w reh.

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5

Gasenzer, Thomas, Boris Nowak, and Dénes Sexty. "Charge separation in reheating after cosmological inflation." Physics Letters B 710, no. 4-5 (April 2012): 500–503. http://dx.doi.org/10.1016/j.physletb.2012.03.031.

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6

Kabir, Rakesh, Amitabha Mukherjee, and Daksh Lohiya. "Reheating constraints on Kähler moduli inflation." Modern Physics Letters A 34, no. 15 (May 20, 2019): 1950114. http://dx.doi.org/10.1142/s0217732319501141.

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The end of inflation is connected to the standard cosmological scenario through reheating. During reheating, the inflaton oscillates around the minimum of the potential and thus decays into the daughter particles that populate the Universe at later times. Using cosmological evolution for observable CMB scales from the time of Hubble crossing to the present time, we translate the constraint on the spectral index [Formula: see text] from Planck data to the constraint on the reheating scenario in the context of Kähler moduli inflation. We find that the equation of state parameter plays a crucial role in the reheating analysis, however the details of the one parameter potential are irrelevant if the analysis is done strictly within the slow-roll formalism. In addition, we extend the de facto analysis generally done only for the pivot scale to all the observable scales which crossed the Hubble radius during inflation, where we study how the maximum number of e-folds varies for different scales, and the effect of the equation of state and potential parameters.

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7

Germán, Gabriel, R. Gonzalez Quaglia, and A. M. Moran Colorado. "Model independent bounds for the number of e-folds during the evolution of the universe." Journal of Cosmology and Astroparticle Physics 2023, no. 03 (March 1, 2023): 004. http://dx.doi.org/10.1088/1475-7516/2023/03/004.

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Abstract We present a simple procedure to obtain universal bounds for quantities of cosmological interest, such as the number of e-folds during inflation, reheating, and radiation, as well as the reheating temperature. The main assumption is to represent each of the various epochs of evolution of the universe as being due to a single substance changing instantaneously into the next, describing a new era of evolution of the universe. This assumption, commonly used to obtain solutions of the Friedmann equations for simple cosmological models, is implemented here to find model-independent bounds on cosmological quantities of interest. In particular, we find that the bound Nk ≈ 56 for -1/3 < ω re < 1/3 is very robust as an upper bound on the number of e-folds during inflation and also as a lower bound when ω re > 1/3, where ω re is the effective equation of state parameter during reheating. These are model-independent results that any single-field model of inflation should satisfy. As an example we illustrate with the basic α attractor model the usual model dependent approach, and the one presented here, and show how they complement each other.

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8

Sakhi, Z., A. Safsafi, M. Ferricha-Alami, H. Chakir, and M. Bennai. "Observational constraints on reheating in braneworld inflation." International Journal of Modern Physics A 34, no. 27 (September 27, 2019): 1950152. http://dx.doi.org/10.1142/s0217751x19501525.

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The reheating era after inflation is analyzed in the framework of the braneworld models. We study reheating by calculating the reheating temperature in a braneworld inflation for various cosmological parameters. The variation of reheating [Formula: see text]-folding number and reheating temperature were obtained and analyzed as function of a spectrum of perturbation for a polynomial potential [Formula: see text]. We have applied the slow-roll approximation in the high energy limit to constraint the parameter potentials by confronting our results to recent Planck 2018 observations. We have shown that in general the best values of the predicted reheating temperature is of the order [Formula: see text] GeV, with a brane tension [Formula: see text] GeV4. We have also shown that the polynomial potential in the case [Formula: see text] provides the best fit results with recent observational constraints.

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9

Salamate, F., I. Khay, M. Ferricha-Alami, H. Chakir, and M. Bennai. "Reheating Temperature from D-Term Cosmological Inflation Braneworld." Astronomy Reports 63, no. 12 (December 2019): 990–97. http://dx.doi.org/10.1134/s1063772919120059.

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10

Allahverdi, Rouzbeh, and Bruce A. Campbell. "Cosmological reheating and self-interacting final state bosons." Physics Letters B 395, no. 3-4 (March 1997): 169–77. http://dx.doi.org/10.1016/s0370-2693(97)00045-2.

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11

BENTO, M. C., O. BERTOLAMI, and P. M. SÁ. "INFLATION FROM STRINGS II: REHEATING AND BARYOGENESIS." Modern Physics Letters A 07, no. 11 (April 10, 1992): 911–20. http://dx.doi.org/10.1142/s021773239200080x.

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We study the reheating process which takes place after the two periods of inflation that arise from a string-inspired cosmological model. Baryogenesis mechanisms and a possible solution for the magnetic monopole problem that are compatible with string-motivated inflationary scenarios are discussed.

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12

KAYA, ALI. "UNCERTAINTY RELATIONS FOR COSMOLOGICAL PARTICLE CREATION AND EXISTENCE OF LARGE FLUCTUATIONS IN REHEATING." International Journal of Modern Physics D 20, no. 14 (December 31, 2011): 2795–801. http://dx.doi.org/10.1142/s021827181102069x.

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We derive an uncertainty relation for the energy density and pressure of a quantum scalar field in a time-dependent, homogeneous and isotropic, classical background, which implies the existence of large fluctuations comparable to their vacuum expectation values. A similar uncertainty relation is known to hold for the field square since the field can be viewed as a Gaussian random variable. We discuss possible implications of these results for the reheating process in scalar field driven inflationary models, where reheating is achieved by the decay of the coherently oscillating inflaton field. Specifically we argue that the evolution after backreaction can seriously be altered by the existence of these fluctuations. For example, in one model the coherence of the inflaton oscillations is found to be completely lost in a very short time after backreaction starts. Therefore we argue that entering a smooth phase in thermal equilibrium is questionable in such models and reheating might destroy the smoothness attained by inflation.

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13

Artymowski, Michał, Olga Czerwińska, Zygmunt Lalak, and Marek Lewicki. "Gravitational wave signals and cosmological consequences of gravitational reheating." Journal of Cosmology and Astroparticle Physics 2018, no. 04 (April 17, 2018): 046. http://dx.doi.org/10.1088/1475-7516/2018/04/046.

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14

Gelmini, Graciela, Efunwande Osoba, Sergio Palomares-Ruiz, and Silvia Pascoli. "MeV sterile neutrinos in low reheating temperature cosmological scenarios." Journal of Cosmology and Astroparticle Physics 2008, no. 10 (October 17, 2008): 029. http://dx.doi.org/10.1088/1475-7516/2008/10/029.

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15

Kaya, Ali, and Emine Seyma Kutluk. "Entropy mode loops and cosmological correlations during perturbative reheating." Journal of Cosmology and Astroparticle Physics 2015, no. 01 (January 19, 2015): 026. http://dx.doi.org/10.1088/1475-7516/2015/01/026.

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16

BIRRELL, JEREMIAH, CHENG-TAO YANG, PISIN CHEN, and JOHANN RAFELSKI. "FUGACITY AND REHEATING OF PRIMORDIAL NEUTRINOS." Modern Physics Letters A 28, no. 40 (December 23, 2013): 1350188. http://dx.doi.org/10.1142/s0217732313501885.

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We clarify in a quantitative way the impact that distinct chemical Tc and kinetic Tk freeze-out temperatures have on the reduction of the neutrino fugacity ϒν below equilibrium, i.e. ϒν<1, and the increase of the neutrino temperature Tν via partial reheating. We establish the connection between ϒν and Tk via the modified reheating relation Tν(ϒν)/Tγ, where Tγ is the temperature of the background radiation. Our results demonstrate that one must introduce the chemical nonequilibrium parameter, i.e. the fugacity, ϒν, as an additional standard cosmological model parameter in the evaluation of CMB fluctuations as its value allows measurement of Tk.

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17

GELMINI, GRACIELA B. "COSMOLOGY OF "VISIBLE" STERILE NEUTRINOS." International Journal of Modern Physics A 20, no. 19 (July 30, 2005): 4670–75. http://dx.doi.org/10.1142/s0217751x05028363.

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We point out that in scenarios with a low reheating temperature TR << 100 MeV at the end of (the last episode of) inflation or entropy production, the abundance of sterile neutrinos becomes largely independent of their coupling to active neutrinos. Thus, cosmological bounds become less stringent than usually assumed, allowing sterile neutrinos to be "visible" in future experiments. For example, the sterile neutrino required by the LSND result does not have any cosmological problem within these scenarios.

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18

Farajollahi, Hossein, and Arvin Ravanpak. "Curvaton reheating and intermediate inflation in brane cosmology." Canadian Journal of Physics 89, no. 10 (October 2011): 1015–21. http://dx.doi.org/10.1139/p11-087.

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In this paper, we study the curvaton reheating mechanism for an intermediate inflationary universe in brane world cosmology. In contrast to our previous work, we assume that when the universe enters the kination era, it is still in the high-energy regime. We then discuss, in detail, the new cosmological constraints on both the model parameters and the physical quantities.

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19

Cárdenas, Víctor H., Sergio del Campo, and Ramón Herrera. "R2-Corrections to Chaotic Inflation." Modern Physics Letters A 18, no. 29 (September 21, 2003): 2039–49. http://dx.doi.org/10.1142/s0217732303011691.

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Scalar density cosmological perturbations, spectral indices and reheating in a chaotic inflationary universe model, in which a higher derivative term is added, are investigated. This term is supposed to play an important role in the early evolution of the Universe, specifically at times closer to the Planck era.

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20

Aresté Saló, L., D. Benisty, E. I. Guendelman, and J. d. Haro. "Quintessential inflation and cosmological seesaw mechanism: reheating and observational constraints." Journal of Cosmology and Astroparticle Physics 2021, no. 07 (July 1, 2021): 007. http://dx.doi.org/10.1088/1475-7516/2021/07/007.

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21

Graef, L. L., W. S. Hipólito-Ricaldi, Elisa G. M. Ferreira, and Robert Brandenberger. "Dynamics of cosmological perturbations and reheating in the anamorphic universe." Journal of Cosmology and Astroparticle Physics 2017, no. 04 (April 3, 2017): 004. http://dx.doi.org/10.1088/1475-7516/2017/04/004.

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22

Nambu, Y., and A. Taruya. "Evolution of Cosmological Perturbation in Reheating Phase of the Universe." Progress of Theoretical Physics 97, no. 1 (January 1, 1997): 83–89. http://dx.doi.org/10.1143/ptp.97.83.

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23

Taruya, A., and Y. Nambu. "Cosmological perturbation with two scalar fields in reheating after inflation." Physics Letters B 428, no. 1-2 (May 1998): 37–43. http://dx.doi.org/10.1016/s0370-2693(98)00378-5.

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24

CHOI, JEONG RYEOL. "QUANTUM ANALYSIS FOR THE EVOLUTION OF THE COSMOLOGICAL CONSTANT VIA UNITARY TRANSFORMATION." International Journal of Modern Physics D 16, no. 07 (July 2007): 1119–32. http://dx.doi.org/10.1142/s0218271807010602.

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The expectation value of the vacuum energy density tied to the cosmological constant is derived from the non-relativistic quantum description of the reheating process using the unitary transformation method. Our research is performed for two special cases, i.e. under the assumption of two different duration terms for the radiation-dominated era. We suppose that the radiation-dominated era lasted for 3,000 years in the first case, and for a very short time so that it can be ignored in the other case. For the former case, the resulting present cosmological constant is much higher than the previously known one. However, for the latter case, it is in good agreement with that obtained from recent cosmic microwave background radiation measurements. Hence, we cannot exclude the possibility that the change of the universe from the radiation-dominated era to the matter-dominated era might have progressed very swiftly after the beginning of reheating. The analysis shows that the vacuum energy density has been dissipated by the nonconservative force acting on the coherent oscillations of the scalar field according to the expansion of the universe.

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25

Alam, Khursid, and Koushik Dutta. "Effects of reheating on moduli stabilization." Journal of Cosmology and Astroparticle Physics 2022, no. 10 (October 1, 2022): 085. http://dx.doi.org/10.1088/1475-7516/2022/10/085.

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Abstract Moduli potential loses its minima due to external energy sources of inflaton energy density or radiation produced at the end of inflation. But, the non-existence of minima does not necessarily mean destabilization of moduli. In fact, the destabilization of moduli is always dependent on the initial field values of the fields. In this work, we study carefully how the effects of reheating ease the problem of moduli destabilization. The associated time scale to produce the thermal bath allows a larger initial field range to stabilize the field. Contrary to the usual notion, the allowed initial field range is larger for higher temperatures when the effective potential is of a run-away nature. This eases the moduli destabilization problem for heavy mass moduli. For low mass moduli (≲ 30 TeV), the allowed field range still causes the cosmological moduli problem by violating the BBN constraints unless its initial abundance is suppressed.

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26

Xue, She-Sheng. "Cosmological constant, matter, cosmic inflation and coincidence." Modern Physics Letters A 35, no. 15 (April 14, 2020): 2050123. http://dx.doi.org/10.1142/s0217732320501230.

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We present a possible understanding to the issues of cosmological constant, inflation, dark matter and coincidence problems based only on the Einstein equation and Hawking particle production. The inflation appears and results agree to observations. The CMB large-scale anomaly can be explained and the dark-matter acoustic wave is speculated. The entropy and reheating are discussed. The cosmological term [Formula: see text] tracks down the matter [Formula: see text] until the radiation-matter equilibrium, then slowly varies, thus the cosmic coincidence problem can be avoided. The relation between [Formula: see text] and [Formula: see text] is shown and can be examined at large redshifts.

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27

CARNEIRO, SAULO. "COSMOLOGICAL CONCORDANCE MODEL WITH PARTICLE CREATION." International Journal of Modern Physics: Conference Series 18 (January 2012): 38–47. http://dx.doi.org/10.1142/s2010194512008173.

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The creation of ultra-light dark particles in the late-time FLRW spacetime provides a cosmological model in accordance with precise observational tests. The matter creation backreaction implies in this context a vacuum energy density scaling linearly with the Hubble parameter H, which is consistent with the vacuum expectation value of the QCD condensate in a low-energy expanding spacetime. Both the cosmological constant and coincidence problems are alleviated in this scenario. We also explore the opposite, high energy limit of the particle creation process. We show that it leads to a non-singular primordial universe where an early inflationary era takes place, with natural reheating and exit. The generated primordial spectrum is scale invariant and, by supposing that inflation lasts for 60 e-folds, we obtain a scalar expectral index n ≈ 0.97.

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28

KAYA, ALI. "COSMOLOGICAL PARTICLE CREATION: FLUCTUATIONS AND AN ENSEMBLE PICTURE." International Journal of Modern Physics D 17, no. 13n14 (December 2008): 2441–45. http://dx.doi.org/10.1142/s0218271808013935.

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We point out that in the context of quantum fields in time-dependent classical backgrounds, the number of created particles with a given momentum largely deviates about its mean value. Since the corresponding Fourier modes are nonlocal, this deviation shows that the expectation value of the number operator can make sense only in an ensemble of space–times. Using a complete orthonormal family of localized wave packets, we show how an ensemble interpretation can be given to cosmological particle creation in local terms. The reheating process following inflation is re-examined in the light of this construction.

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29

DYMNIKOVA, IRINA, and MAXIM KHLOPOV. "DECAY OF COSMOLOGICAL CONSTANT AS BOSE CONDENSATE EVAPORATION." Modern Physics Letters A 15, no. 38n39 (December 21, 2000): 2305–14. http://dx.doi.org/10.1142/s0217732300002966.

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We consider the process of decay of symmetric vacuum state as evaporation of a Bose condensate of physical Higgs particles, defined over asymmetric vacuum state. Energy density of their self-interaction is identified with cosmological constant Λ in the Einstein equation. Λ decay then provides dynamical realization of spontaneous symmetry breaking. The effective mechanism is found for damping of coherent oscillations of a scalar field, leading to slow evaporation regime as the effective mechanism for Λ decay responsible for inflation without special fine-tuning of the microphysical parameters. This mechanism is able to incorporate reheating, generation of proper primordial fluctuations, and nonzero cosmological constant today.

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30

Hasegawa, Takuya, Nagisa Hiroshima, Kazunori Kohri, Rasmus S. L. Hansen, Thomas Tram, and Steen Hannestad. "MeV-scale reheating temperature and cosmological production of light sterile neutrinos." Journal of Cosmology and Astroparticle Physics 2020, no. 08 (August 6, 2020): 015. http://dx.doi.org/10.1088/1475-7516/2020/08/015.

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31

Shojaee, R., K. Nozari, and F. Darabi. "α-Attractors and reheating in a class of Galileon inflation." International Journal of Modern Physics D 30, no. 05 (February 25, 2021): 2150036. http://dx.doi.org/10.1142/s021827182150036x.

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We study cosmological inflation in a Galileon inflationary model with the E-model potential to find possible [Formula: see text]-attractors. First, we calculate evolution of the perturbations in our setup. By adopting E-model potential, we show that values of the scalar spectral index and tensor-to-scalar ratio are universal. Also, we consider the reheating phase after inflation in this model. We compare the results with the Planck data and we find some constraints on the model’s parameter space. We find that in a Galileon inflation model, the reheating phase can last longer than that in the Standard Model. Also, in this model, the larger range of temperature is corresponding to observational viable values of [Formula: see text].

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32

Ghayour, Basem. "The investigation of detectability of the relic gravitational waves based on the WMAP-9 and Planck." International Journal of Modern Physics D 26, no. 02 (February 2017): 1750003. http://dx.doi.org/10.1142/s0218271817500031.

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The generated relic gravitational waves underwent several stages of evolution of the universe such as inflation and reheating. These stages were affected on the shape of spectrum of the waves. As well known, at the end of inflation, the scalar field [Formula: see text] oscillates quickly around some point where potential [Formula: see text] has a minimum. The end of inflation stage played a crucial role on the further evolution stages of the universe because particles were created and collisions of the created particles were responsible for reheating the universe. There is a general range for the frequency of the spectrum [Formula: see text])[Formula: see text]Hz. It is shown that the reheating temperature can affect on the frequency of the spectrum as well. There is constraint on the temperature from cosmological observations based on WMAP-9 and Planck. Therefore, it is interesting to estimate allowed value of frequencies of the spectrum based on general range of reheating temperature like few MeV [Formula: see text] GeV, WMAP-9 and Planck data then compare the spectrum with sensitivity of future detectors such as LISA, BBO and ultimate-DECIGIO. The obtained results of this comparison give us some more chance for detection of the relic gravitational waves.

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33

Popa, Lucia Aurelia. "Search for Dark Higgs Inflation with Curvature Corrections at LHC Experiments." Universe 8, no. 4 (April 12, 2022): 235. http://dx.doi.org/10.3390/universe8040235.

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We analyse the dark Higgs inflation model with curvature corrections and explore the possibility to test its predictions by the particle physics experiments at LHC. We show that the dark Higgs inflation model with curvature corrections is strongly favoured by the present cosmological observation. The cosmological predictions of this model, including the quantum corrections of dark Higgs coupling constants and the uncertainty in estimation of the reheating temperature, lead to the dark Higgs mass mφ=0.919± 0.211 GeV and the mixing angle (at 68% CL). We evaluate the FASER and MAPP-1 experiments reach for dark Higgs inflation mass and mixing angle in the 95% CL cosmological confidence region for an integrated luminosity of 3ab−1 at 13 TeV LHC, assuming 100% detection efficiency. We conclude that the dark Higgs inflation model with curvature corrections is a compelling inflation scenario based on particle physics theory favoured by the present cosmological measurements that can leave imprints in the dark Higgs boson searchers at LHC.

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34

Francis, Ng K. "Cosmic Baryon Asymmetry in Different Neutrino Mass Models with Mixing Angles." Advances in High Energy Physics 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/689719.

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We investigate the comparative studies of cosmological baryon asymmetry in different neutrino mass models with and withoutθ13by considering the three-diagonal form of Dirac neutrino mass matrices and the three aspects of leptogenesis, unflavoured, flavoured, and nonthermal. We found that the estimations of any models withθ13are consistent in all the three stages of calculations of leptogenesis and the results are better than the predictions of any models withoutθ13which are consistent in a piecemeal manner with the observational data in all the three stages of leptogenesis calculations. For the normal hierarchy of Type-IA with charged lepton matrix, model with and withoutθ13predicts inflaton mass required to produce the observed baryon asymmetry to beMϕ~2.2×1011 GeV andMϕ~3.6×1010 GeV, and the corresponding reheating temperatures areTR~4.86×106 GeV andTR~4.50×106 GeV respectively. These predictions are not in conflict with the gravitino problem which required the reheating temperature to be below107 GeV. And these values apply to the recent discovery of Higgs boson of mass~125 GeV. One can also have the right order of relic dark matter abundance only if the reheating temperature is bounded to below107 GeV.

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35

Su, Juntong, Tiberiu Harko, and Shi-Dong Liang. "Irreversible Thermodynamic Description of Dark Matter and Radiation Creation during Inflationary Reheating." Advances in High Energy Physics 2017 (October 18, 2017): 1–24. http://dx.doi.org/10.1155/2017/7650238.

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We investigate matter creation processes during the reheating period of the early Universe, by using the thermodynamic of open systems. The Universe is assumed to consist of the inflationary scalar field, which, through its decay, generates relativistic matter and pressureless dark matter. The inflationary scalar field transfers its energy to the newly created matter particles, with the field energy decreasing to near zero. The equations governing the irreversible matter creation are obtained by combining the thermodynamics description of the matter creation and the gravitational field equations. The role of the different inflationary scalar field potentials is analyzed by using analytical and numerical methods. The values of the energy densities of relativistic matter and dark matter reach their maximum when the Universe is reheated up to the reheating temperature, which is obtained as a function of the scalar field decay width, the scalar field particle mass, and the cosmological parameters. Particle production leads to the acceleration of the Universe during the reheating phase, with the deceleration parameter showing complex dynamics. Once the energy density of the scalar field becomes negligible with respect to the matter densities, the expansion of the Universe decelerates, and inflation has a graceful exit.

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36

Harko, T., W. F. Choi, K. C. Wong, and K. S. Cheng. "Reheating the Universe in braneworld cosmological models with bulk–brane energy transfer." Journal of Cosmology and Astroparticle Physics 2008, no. 06 (June 2, 2008): 002. http://dx.doi.org/10.1088/1475-7516/2008/06/002.

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37

Choudhury, Sayantan. ":THE COSMOLOGICAL OTOC: Formulating New Cosmological Micro-Canonical Correlation Functions for Random Chaotic Fluctuations in Out-Of-Equilibrium Quantum Statistical Field Theory." Symmetry 12, no. 9 (September 16, 2020): 1527. http://dx.doi.org/10.3390/sym12091527.

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The out-of-time-ordered correlation (OTOC) function is an important new probe in quantum field theory which is treated as a significant measure of random quantum correlations. In this paper, using for the first time the slogan “Cosmology meets Condensed Matter Physics”, we demonstrate a formalism to compute the Cosmological OTOC during the stochastic particle production during inflation and reheating following the canonical quantization technique. In this computation, two dynamical time scales are involved—out of them, at one time scale, the cosmological perturbation variable, and for the other, the canonically conjugate momentum, is defined, which is the strict requirement to define the time scale-separated quantum operators for OTOC and is perfectly consistent with the general definition of OTOC. Most importantly, using the present formalism, not only one can study the quantum correlation during stochastic inflation and reheating, but can also study quantum correlation for any random events in Cosmology. Next, using the late time exponential decay of cosmological OTOC with respect to the dynamical time scale of our universe which is associated with the canonically conjugate momentum operator in this formalism, we study the phenomenon of quantum chaos by computing the expression for the Lyapunov spectrum. Furthermore, using the well known Maldacena Shenker Stanford (MSS) bound on the Lyapunov exponent, λ≤2π/β, we propose a lower bound on the equilibrium temperature, T=1/β, at the very late time scale of the universe. On the other hand, with respect to the other time scale with which the perturbation variable is associated, we find decreasing, but not exponentially decaying, behaviour, which quantifies the random quantum correlation function out-of-equilibrium. We have also studied the classical limit of the OTOC and checked the consistency with the large time limiting behaviour of the correlation. Finally, we prove that the normalized version of OTOC is completely independent of the choice of the preferred definition of the cosmological perturbation variable.

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38

Krajewski, Tomasz, and Krzysztof Turzyński. "(P)reheating and gravitational waves in α-attractor models." Journal of Cosmology and Astroparticle Physics 2022, no. 10 (October 1, 2022): 005. http://dx.doi.org/10.1088/1475-7516/2022/10/005.

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Abstract We study post-inflationary evolution in α-attractor T-models of inflation. We consider the dynamics of both scalar fields present in these models: the inflaton and the spectator, as a negative field-space curvature may lead to geometrical destabilization of the spectator. We perform state-of-the-art lattice simulations with a dedicated numerical code optimized for those models. We corroborate earlier findings that the perturbations of the spectator field are much more unstable than the perturbations of the inflaton field, so the dynamics of early stages of preheating is dominated by the evolution of spectator perturbations. We also calculate the spectrum of gravitational waves originating from scalar fluctuations in order to determine if the α-attractor T-models can be constrained or even ruled out by present cosmological observations, but not by direct searches of gravitational waves.

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Neves, R. M. P., S. Santos da Costa, F. A. Brito, and J. S. Alcaniz. "Brane inflation driven by an arctan potential: CMB constraints and reheating." Journal of Cosmology and Astroparticle Physics 2022, no. 07 (July 1, 2022): 024. http://dx.doi.org/10.1088/1475-7516/2022/07/024.

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Abstract We investigate the early universe evolution in the context of brane inflation driven by a supergravity-inspired arctan potential. We performed a slow-roll and a semi-analytical reheating analyses and obtained constraints on the inflationary parameters in agreement with Planck 2018 data. We also employed a Markov Chain Monte Carlo analysis to perform a parameter estimation of the cosmological parameters, obtaining results in good agreement with the currently available cosmic microwave background and baryon acoustic oscillation data. This work establishes the general theoretical predictions of the arctan model, with the results of the statistical analysis corroborating its observational viability.

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40

GUENDELMAN, E. I., and A. B. KAGANOVICH. "GRAVITY, COSMOLOGY AND PARTICLE PHYSICS WITHOUT THE COSMOLOGICAL CONSTANT PROBLEM." Modern Physics Letters A 13, no. 19 (June 21, 1998): 1583–86. http://dx.doi.org/10.1142/s0217732398001662.

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This letter elucidates recent achievements of the "nongravitating vacuum energy (NGVE) theory" which has the feature that a shift of the Lagrangian density by a constant does not affect dynamics. In the first-order formalism, a constraint appears that enforces the vanishing of the cosmological constant Λ. Standard dynamics of gauge unified theories (including fermions) and their SSB appear if a four-index field strength condensate is present. At the vacuum state, there is exact balance (to zero) of the gauge fields condensate and the original scalar fields potential. As a result it is possible to combine the solution of the Λ problem with inflation and transition to a Λ=0 phase without fine tuning after a reheating period. The model opens new possibilities for a solution of the hierarchy problem.

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41

Capozziello, S., A. Carleo, and G. Lambiase. "The amplification of cosmological magnetic fields in extended f(T,B) teleparallel gravity." Journal of Cosmology and Astroparticle Physics 2022, no. 10 (October 1, 2022): 020. http://dx.doi.org/10.1088/1475-7516/2022/10/020.

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Abstract Observations indicate that intergalactic magnetic fields have amplitudes of the order of ∼ 10-6 G and are uniform on scales of ∼ 10 kpc. Despite their wide presence in the Universe, their origin remains an open issue. Even by invoking a dynamo mechanism or a compression effect for magnetic field amplification, the existence of seed fields before galaxy formation is still problematic. General Relativity predicts an adiabatic decrease of the magnetic field evolving as |B| ∝ 1/a 2, where a is the scale factor of the Universe. It results in very small primordial fields, unless the conformal symmetry of the electromagnetic sector is broken. In this paper, we study the possibility that a natural mechanism for the amplification of primordial magnetic field can be related to extended teleparallel gravity f(T,B) models, where T is the torsion scalar, and B the boundary term. In particular, we consider a non-minimal coupling with gravity in view to break conformal symmetry in a teleparallel background, investigating, in particular, the role of boundary term B, which can be consider as a further scalar field. We find that, after solving exactly the f(T,B) field equations both in inflation and reheating eras, a non-adiabatic behavior of the magnetic field is always possible, and a strong amplification appears in the reheating epoch. We also compute the ratio r = ρB /ργ between the magnetic energy density and the cosmic microwave energy density during inflation, in order to explain the present value r ≃ 1, showing that, in the slow-roll approximation, power-law teleparallel theories with Bn have effects indistinguishable from metric theories Rn where R is the Ricci curvature scalar.

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42

Rashidi, Narges, and Kourosh Nozari. "α-Attractor and reheating in a model with noncanonical scalar fields." International Journal of Modern Physics D 27, no. 07 (May 2018): 1850076. http://dx.doi.org/10.1142/s0218271818500761.

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We consider two noncanonical scalar fields [tachyon and Dirac–Born–Infeld (DBI)] with E-model type of the potential. We study cosmological inflation in these models to find possible [Formula: see text]-attractors. We show that similar to the canonical scalar field case, in both tachyon and DBI models there is a value of the scalar spectral index in small [Formula: see text] limit which is just a function of the e-folds number. However, the value of [Formula: see text] in DBI model is somewhat different from the other ones. We also compare the results with Planck2015 TT, TE, EE+lowP data. The reheating phase after inflation is studied in these models which gives some more constraints on the model parameters.

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Dent, Thomas. "Baryogenesis with Four-Fermion Operators in Low-Scale Models." International Journal of Modern Physics A 18, supp01 (February 2003): 320–28. http://dx.doi.org/10.1142/s0217751x03016690.

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We describe a nonstandard proposal for baryogenesis in models with a low ([Formula: see text](10 – 100)TeV) fundamental scale. The scenario has Standard Model field content and enhanced baryon number violating operators deriving from time-dependent fermion localization in an extra dimension. The CKM matrix provides sufficient CP violation. The major constraints are the low reheating temperature and rate of perturbative B-violating reactions compared to the total entropy created. A sufficient baryon fraction may arise, but the cosmological evolution required is likely to be somewhat contrived. Based on work in collaboration with D.J.H. Chung.

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44

Bertolami, Orfeu, and Jorge Páramos. "Minimal extension of General Relativity: Alternative gravity model with non-minimal coupling between matter and curvature." International Journal of Geometric Methods in Modern Physics 11, no. 02 (February 2014): 1460003. http://dx.doi.org/10.1142/s0219887814600032.

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We examine an extension of General Relativity with an explicit non-minimal coupling between matter and curvature. The purpose of this work is to present an overview of the implications of the latter to various contexts, ranging from astrophysical matter distributions to a cosmological setting. Various results are discussed, including the impact of this non-minimal coupling on the choice of Lagrangian density, on a mechanism to mimic galactic and cluster dark matter, on the possibility of accounting for the accelerated expansion of the Universe, energy density fluctuations and modifications to post-inflationary reheating. The equivalence between a model exhibiting a non-minimal coupling and multi-scalar-theories is also discussed.

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45

Chiu, Weihsueh A., and Jeremiah P. Ostriker. "A Semianalytic Model for Cosmological Reheating and Reionization Due to the Gravitational Collapse of Structure." Astrophysical Journal 534, no. 2 (May 10, 2000): 507–32. http://dx.doi.org/10.1086/308780.

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46

León, Gabriel. "Inflation and the cosmological (not-so) constant in unimodular gravity." Classical and Quantum Gravity 39, no. 7 (March 7, 2022): 075008. http://dx.doi.org/10.1088/1361-6382/ac52bc.

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Abstract We propose a mechanism for generating an inflationary phase in the early universe without resorting to any type of scalar field(s). Instead, this accelerated expansion is driven by a dynamical ‘cosmological constant (CC)’ in the framework of unimodular gravity (UG). The time dependent CC can be related to an energy diffusion term that arises naturally in UG due to its restrictive diffeomorphism invariance. We derive the generic conditions required for any type of diffusion to generate a realistic inflationary epoch. Furthermore, for a given parameterization of inflation (in terms of the Hubble flow functions), we show how to construct the corresponding diffusion term in such a way that a smooth transition occurs between inflation and the subsequent radiation dominated era, hence reheating proceeds naturally. The primordial spectrum is obtained during the inflationary phase by considering inhomogeneous perturbations associated to standard hydrodynamical matter (modeled as a single ultra-relativistic fluid). We demonstrate that the resulting spectrum is equivalent to that obtained in traditional inflationary models, and is also independent of the particular form of the diffusion term. In addition, we analyze the feasibility of identifying the variable CC, responsible for the inflationary expansion, with the current observed value.

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47

Ghoshal, Anish, Gaetano Lambiase, Supratik Pal, Arnab Paul, and Shiladitya Porey. "Post-Inflationary Production of Dark Matter after Inflection Point Slow Roll Inflation." Symmetry 15, no. 2 (February 17, 2023): 543. http://dx.doi.org/10.3390/sym15020543.

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We explore a feasible model that combines near-inflection point small-field slow roll inflationary scenario driven by single scalar inflaton with the production of non-thermal vector-like fermionic dark matter, χ, during the reheating era. For the inflationary scenario, we consider two separate polynomial forms of the potential; one is symmetric about the origin, and the other is not. We fix the coefficients of the potentials satisfying current Planck-Bicep data. We calculate the permissible range of yχ and mχ for the production of enough dark matter to explain the total Cold Dark Matter (CDM) mass density of the present universe while satisfying Cosmic Background Radiation (CMBR) measurements and other cosmological bounds.

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48

KETOV, SERGEI V. "MODIFIED SUPERGRAVITY AND EARLY UNIVERSE: THE MEETING POINT OF COSMOLOGY AND HIGH-ENERGY PHYSICS." International Journal of Modern Physics A 28, no. 15 (June 16, 2013): 1330021. http://dx.doi.org/10.1142/s0217751x13300214.

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We review the new theory of modified supergravity, dubbed the [Formula: see text] supergravity, and some of its recent applications to inflation and reheating in the early universe cosmology. The [Formula: see text] supergravity is the N = 1 locally supersymmetric extension of the f(R) gravity in four space–time dimensions. A manifestly supersymmetric formulation of the [Formula: see text] supergravity exist in terms of N = 1 superfields, by using the (old) minimal Poincaré supergravity in curved superspace. We find the conditions for stability, the absence of ghosts and tachyons. Three models of the [Formula: see text] supergravity are studied. The first example is devoted to a recovery of the standard (pure) N = 1 supergravity with a negative cosmological constant from the [Formula: see text] supergravity. As the second example, a generic [Formula: see text] supergravity is investigated, and the existence of the AdS bound on the scalar curvature is found. As the third (and most important) example, a simple viable realization of chaotic inflation in supergravity is found. Our approach is minimalistic since it does not introduce new exotic fields or new interactions, beyond those already present in (super)gravity. The universal reheating mechanism is automatic. We establish the consistency of our approach and also apply it to preheating and reheating after inflation. The Higgs inflation and its correspondence to the Starobinsky inflation are established in the context of supergravity. We briefly review other relevant issues such as non-Gaussianity, CP-violation, origin of baryonic asymmetry, lepto- and baryo-genesis. The [Formula: see text] supergravity has promise for possible solutions to those outstanding problems too.

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49

Ferrantelli, Andrea, and John McDonald. "Cosmological evolution of scalar fields and gravitino dark matter in gauge mediation at low reheating temperatures." Journal of Cosmology and Astroparticle Physics 2010, no. 02 (February 3, 2010): 003. http://dx.doi.org/10.1088/1475-7516/2010/02/003.

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50

DYMNIKOVA, I., and M. KRAWCZYK. "EQUATION OF STATE AND TEMPERATURE OF MASSIVE NONRELATIVISTIC BOSONS ARISING IN THE UNIVERSE AT THE FIRST STAGE OF REHEATING." Modern Physics Letters A 10, no. 40 (December 28, 1995): 3069–76. http://dx.doi.org/10.1142/s0217732395003203.

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We consider heavy nonrelativistic bosons with masses M~MGUT which arise in the Universe during phase transitions with spontaneous symmetry breaking at the grand unification scale. In the frame of statistical mechanics approach with model-independent description of cosmological background we show that the process of emerging of massive GUT bosons looks like evaporation of a Bose condensate. First massive nonrelativistic bosons behave like ideal quantum degenerate Bose gas which has the Gibbons-Hawking temperature due to the presence of the de Sitter event horizon.

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