Article
Astronomy & Astrophysics
Carlos Maldonado, Fernando Mendez
Summary: The study focuses on the early stage of universe evolution with two scale factors and interaction between causally disconnected patches. Numerical analysis shows energy transfer between sectors, providing constraints on the deformation parameter, with considerations for energy density decay before Big Bang Nucleosynthesis temperature. The study also addresses implications for nonstandard cosmologies.
Article
Astronomy & Astrophysics
Norbert Bodendorfer, Fabian Haneder
Summary: This paper discusses the coarse graining operation of spatially homogeneous quantum states based on an SU(1,1) Lie group structure and its application in loop quantum cosmology. It also generalizes previous results and implies immediate generalization to other Lie groups based on group theoretical insights.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Astronomy & Astrophysics
Vladimir Toussaint, Jorma Louko
Summary: The study examines the effects of quantized massive scalar fields in spatially compact cosmological spacetimes, showing that the freedom in respective in and out states is determined by two real parameters in the presence of a massive zero mode. Analyzing both untwisted and twisted scalar fields in specific spacetime, it is demonstrated that the choice of massive in zero mode state significantly impacts the response of an inertial Unruh-DeWitt detector, particularly in the excitation part of the spectrum. Special considerations are given to the detector's peculiar velocity with respect to comoving cosmological observers, with the strongest effect observed in the in vacuum of the untwisted field.
Article
Physics, Multidisciplinary
Rajmadan Lakshmanan, Alois Pichler
Summary: This contribution investigates the properties and robustness of the entropy-regularized quantization problem and proposes an approximation technique using the softmin function. The quality of the approximation is evaluated using the entropy-regularized Wasserstein distance. The method's performance is empirically illustrated in various scenarios.
Article
Astronomy & Astrophysics
Alejandro Garcia-Quismondo, Guillermo A. Mena Marugan
Summary: This article reexamines the derivation of dynamical equations of the Ashtekar-Olmedo-Singh black hole model and proposes a more general choice for parameters to be treated as true constants of motion. The consequences of this choice are analyzed, and the compatibility of the proposed procedure with previous results is investigated. The discussion is focused solely on dynamical issues.
FRONTIERS IN ASTRONOMY AND SPACE SCIENCES
(2021)
Article
Astronomy & Astrophysics
Viqar Husain, Jarod George Kelly, Robert Santacruz, Edward Wilson-Ewing
Summary: By studying the quantum dynamics of Lema??tre-Tolman-Bondi space-times using a polymer quantization prescription, we have obtained important insights such as the evolution of dynamical horizons, non-singular bounce phenomena, the relationship between black hole lifetime and mass, and the modification of the traditional "information loss" picture.
Article
Astronomy & Astrophysics
Cong Zhang
Summary: In this research, the loop quantum theory is applied to the spherically symmetric model of gravity coupled to Gaussian dust fields to study the quantum features of black holes. By utilizing the path integral formulation, the quantum dynamics are investigated and an effective action is obtained to describe the continuous description of the quantum lattice system. The derived Hamiltonian in this study differs from the classical Hamiltonian with the holonomy correction for macro black holes, requiring a sufficiently fine lattice structure.
Article
Astronomy & Astrophysics
Patrick Fraser
Summary: In this paper, the fluctuations of Gaussian states in LQC are derived, showing that they diverge as the state variance increases contrary to ordinary quantum mechanics. However, by scaling the holonomy length with a volume regularization parameter, these fluctuations can be arbitrarily suppressed.
Article
Physics, Particles & Fields
Xiangdong Zhang
Summary: This paper extends the thermodynamic properties of loop quantum cosmology (LQC) to a new model with the Lorentz term, showing that the effective density and effective pressure in the modified Friedmann equation not only determine the evolution of the universe but also serve as thermodynamic quantities. The first law of thermodynamics of LQC remains valid with the help of the Misner-Sharp energy, providing precise physical meaning to the effective matter density and effective pressure.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Bao-Fei Li, Parampreet Singh
Summary: We investigate how different loop quantization prescriptions affect the formation of trapped surfaces in gravitational collapse, focusing on the mu o scheme and its drawbacks, as well as the improved dynamics in the mu over bar scheme. It is found that trapped surfaces do not form in the mu o scheme for a nonsingular collapse of homogeneous dust cloud unless certain conditions are met, while black holes can form in the mu over bar scheme and other lattice refinements determined by quantum geometry.
Article
Astronomy & Astrophysics
Beatriz Elizaga Navascues, Alejandro Garcia-Quismondo, Guillermo A. Mena Marugan
Summary: This study investigates the Hamiltonian formulation of the Ashtekar-Olmedo-Singh model for the description of nonrotating, uncharged black holes' interior geometry. The study finds that by incorporating loop quantum effects through the introduction of regularization parameters and using an extended phase space formalism, as well as adopting proper prescriptions, a consistent Hamiltonian derivation of the dynamics and the formal expression of the physical states can be achieved.
Article
Physics, Multidisciplinary
Jin Zhang
Summary: In this study, the scalar one-loop four-point function with one massless vertex is analytically evaluated using the loop regularization method. The infrared divergent parts and stable parts are well separated, with the former expressed in terms of masses and Mandelstam variables as mu(s) -> 0. The final result is explicitly shown through 44 dilogarithms in the relevant kinematic sector.
COMMUNICATIONS IN THEORETICAL PHYSICS
(2021)
Article
Astronomy & Astrophysics
Martin Bojowald
Summary: Loop quantum cosmology is a conflicted field with both exuberant claims of observability and serious objections against its current formulations. This study presents a non-technical case study on the recent claim that loop quantum cosmology might alleviate anomalies in observations of the cosmic microwave background.
Article
Astronomy & Astrophysics
Beatriz Elizaga Navascues, Guillermo A. Menagan, Santiago Prado
Summary: This study examines the compatibility of the quantum homogeneity and isotropy hypothesis with the requirement for a non-oscillatory power spectrum in loop quantum cosmology. It identifies a step in the procedure followed by the authors that is not clearly specified, relating to the switch from one set of states allowed by the hypothesis to a more manageable alternative set. The research shows that the criteria for restricting the vacuum state in LQC are compatible and not mutually exclusive.
Article
Astronomy & Astrophysics
Mercedes Martin-Benito, Rita B. Neves, Javier Olmedo
Summary: This study investigates the feasibility of using states of low energy (SLEs) as vacua for cosmological perturbations in hybrid loop quantum cosmology. Two natural choices of smearing functions are identified within this context, with resulting power spectra at the end of inflation being insensitive to the exact shape and support of the smearing function. Preliminary analysis indicates good agreement with observations in terms of the tensor-to-scalar ratio and spectral index, similar to that of standard cosmology.
Article
Physics, Mathematical
G. Navo, E. Elizalde
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2020)
Review
Astronomy & Astrophysics
Emilio Elizalde
Article
Astronomy & Astrophysics
Jaume Haro, Llibert Areste Salo
GENERAL RELATIVITY AND GRAVITATION
(2020)
Review
Astronomy & Astrophysics
Emilio Elizalde
Summary: This is a review of zeta function concepts and its regularization methods, as well as their applications in physical quantities. Additionally, it also discusses topics related to large scale cosmology and the cosmological constant.
Article
Physics, Particles & Fields
Llibert Areste Salo, Jaume Haro
Summary: For exponential type potentials used to depict quintessential inflation, solutions with large n values do not belong to the basin of attraction of the scaling solution. A late time mechanism to exit this behavior and depict correctly the current cosmic acceleration is not needed, but an improvement introducing another parameter is required to deal with the late time acceleration of our universe.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
L. Areste Salo, D. Benisty, E. Guendelman, J. D. Haro
Summary: A new type of quintessential inflation based on the Lorentzian distribution has been introduced, with a simple potential that aligns with recent observations and depicts the acceleration of the universe, including reheating constraints.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Jaume de Haro, Emilio Elizalde
Summary: This is a clear review of some key issues in modern cosmology, where the author uses simple mathematical examples and analogies to aid in understanding. The paper discusses the mathematical singularities in the Big Bang cosmology theory and proposes methods to address them. It also reviews the horizon and flatness problems of the old cosmology model and discusses the current cosmic acceleration. The paper concludes by discussing the reheating stage of the universe after inflation ends.
Review
Astronomy & Astrophysics
Emilio Elizalde
Summary: It is recommended to avoid using grandiose terms like infinity or singularity in describing the cosmos, and instead provide a clear understanding of key concepts for its origin and evolutionary history. This paper argues that there are no infinities in physics and everything that appears in mathematical equations is a result of extrapolation beyond the equations' validity. Several examples are discussed, such as the Big Bang singularity, classical mechanics, electrodynamics, and field theories. The paper also presents a brief overview of the Universe's history and evolution, emphasizing the importance of detailed observations and high-energy physics experiments in expanding our knowledge.
Review
Multidisciplinary Sciences
Emilio Elizalde
Summary: This article discusses the important events during Albert Einstein's visit to Spain and his contributions to modern cosmology. It also introduces the three main theories of relativity and explores the ultimate theory of relativity.
Article
Physics, Particles & Fields
A. Costantini, E. Elizaide
Summary: This study extends the investigation of unimodular Einsteinian gravity in the context of F(R) gravities for constructing anisotropic evolution scenarios. By imposing the unimodular constraint, the metric can be redefined and the desired evolution equations can be obtained. The reconstruction method is demonstrated with characteristic examples.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Jaume de Haro, Llibert Areste Salo
Summary: The study details important inflation models that can explain the accelerated expansion of the universe and reheating process, ultimately aligning with the theory of the Hot Big Bang universe.
Article
Astronomy & Astrophysics
Llibert Areste Salo, Jaume de Haro
Summary: This study numerically calculates the reheating temperature caused by the gravitational production of conformally-coupled superheavy particles during the phase transition from the end of inflation to the beginning of kination in two different quintessential inflation scenarios. It shows that the reheating temperature in both scenarios is higher than expected, contrary to traditional beliefs.
Article
Astronomy & Astrophysics
L. Areste Salo, D. Benisty, E. Guendelman, J. d Haro
Summary: An exponential kind of quintessential inflation potential motivated by supergravity is studied, which belongs to the class of alpha-attractor models. The model accurately depicts the early- and late-time acceleration of the Universe and is compatible with recent observations, showing an effective equation of state equal to -1 for late time cosmic acceleration.
Article
Astronomy & Astrophysics
Weiqiang Yang, Supriya Pan, Llibert Areste Salo, Jaume de Haro
Summary: The study focuses on the energy flow interaction between dark matter and dark energy, using various interaction functions in four distinct cosmic scenarios. The analysis reveals the importance of handling these interaction models with caution.
Article
Astronomy & Astrophysics
Supriya Pan, Jaume de Haro, Weiqiang Yang, Jaume Amoros