Article
Astronomy & Astrophysics
Daniel G. Figueroa, Adrien Florio, Francisco Torrenti, Wessel Valkenburg
Summary: In this paper, lattice techniques for simulating scalar and gauge field dynamics in an expanding universe are comprehensively discussed. The discretization of field theories, numerical algorithms, and lattice formulations for interacting scalar fields and gauge theories are presented. Symplectic integrators with different accuracy levels are provided for each case, along with relevant observables and constraints. The article also introduces the theoretical basis for the CosmoLattice code, a MPI-based package for simulating the non-linear evolution of field theories in an expanding universe.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Takumi Hayashi, Kohei Kamada, Naritaka Oshita, Jun'ichi Yokoyama
Summary: We apply the Lorentzian path integral to analyze the decay of a false vacuum and predict the decay rate. By utilizing the Picard-Lefschetz theory, we deform the integration contour to ensure the convergence of the Lorentzian path integral. Our findings indicate that the nucleation rate of a critical bubble, where the corresponding bounce action is extremized, follows the same exponent as the Euclidean approach. Furthermore, we extend our computation to the nucleation of bubbles larger or smaller than the critical one, where the Euclidean formalism is not applicable.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Dario Bettoni, Asier Lopez-Eiguren, Javier Rubio
Summary: Using classical lattice simulations, this study investigates the symmetry breaking pattern and non-linear evolution of a spectator field coupled to gravity in the post-inflationary dynamics. The results show that the gradient energy density after the transition plays a significant role and grows steadily to equal the kinetic energy. This observation allows for the generic onset of radiation domination, but the produced spectrum is non-thermal.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Wen-Yuan Ai, Bjoern Garbrecht, Carlos Tamarit
Summary: In a first-order phase transition, it is commonly believed that the friction force on the bubble wall is due to a departure from thermal equilibrium in the plasma. However, recent research has shown that even in local equilibrium, an effective friction force exists that scales with the Lorentz factor of the bubble wall velocity. This apparent contradiction is resolved by considering the inhomogeneous temperature distribution of the plasma.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Shao-Jiang Wang, Zi-Yan Yuwen
Summary: This paper proposes an iteration method that takes into account the variation of sound velocity across the bubble wall for a general and realistic equation of state (EoS) beyond the simple bag model and v-model. The study finds a suppression effect for the efficiency factor of bulk fluid motions, though it may be negligible for strong phase transitions.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Kimihiro Nomura, Daisuke Yoshida
Summary: The study focuses on the past-directed extendibility of FLRW and Bianchi type I spacetimes with a vanishing scale factor in the past, providing criteria for determining singularities and exploring the time-dependence of the scale factor in both spacetimes beyond the leading order.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Anna Ijjas, Roman Kolevatov
Summary: This paper explores the entropic mechanism in non-singular bouncing cosmologies, showing that curvature modes are naturally generated during the graceful exit phase. The kinetic energy components play a key role in driving the evolution towards the cosmological bounce.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Stefan Hoche, Jonathan Kozaczuk, Andrew J. Long, Jessica Turner, Yikun Wang
Summary: In this study, we analyzed the expansion of Higgs condensate bubbles during a first-order electroweak phase transition in the early Universe. The interaction of particles with the bubble wall may involve the emission of multiple soft gauge bosons. Resummation to all orders is necessary when the wall velocity is large, and we performed this resummation analytically and numerically at leading logarithmic accuracy. Both approaches agreed to a 10% level, and for fast-moving walls, we found a scaling of the thermal pressure exerted against the wall.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Thomas Biekoetter, Sven Heinemeyer, Jose Miguel No, Maria Olalla Olea-Romacho, Georg Weiglein
Summary: We analyze the thermal history of the 2HDM and find that the presence of vacuum trapping impedes a first-order electroweak phase transition in certain parameter regions. In the regions where the transition does occur, the parameter space for a detectable stochastic gravitational wave signal is constrained and will be well probed by the HL-LHC and measurements of the self-coupling of the Higgs boson at 125 GeV. The ILC has the ability to probe the majority of the 2HDM parameter space with high precision through measurements of the self-coupling.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Glauber C. Dorsch, Stephan J. Huber, Thomas Konstandin
Summary: This study re-evaluates the status of supersonic electroweak baryogenesis using a generalized fluid Ansatz for non-equilibrium distribution functions. By allowing for higher order terms and pointing out inconsistencies in standard treatments of transport, it suggests that baryogenesis may be possible even in the presence of supersonic wall velocities. The analysis supports recent findings and presents the first analysis of baryogenesis using the fluid approximation to higher orders.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Juan Garcia-Bellido, Hitoshi Murayama, Graham White
Summary: It has been suggested that Gaia has the potential to detect a stochastic gravitational wave background in a frequency range ideal for studying phase transitions in early universe cosmology. Additionally, Gaia could be used to differentiate between primordial black holes produced during early universe transitions and those expected from the QCD epoch. Furthermore, Gaia may play a role in exploring topological defects and shedding light on recent NANOGrav results.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Simone Blasi, Ryusuke Jinno, Thomas Konstandin, Henrique Rubira, Isak Stomberg
Summary: This paper discusses the gravitational wave spectrum produced by first-order phase transitions seeded by domain wall networks and its importance in many two-step phase transitions. When the correlation length of the domain wall network is larger than the typical bubble size, the gravitational wave signal is shifted to lower frequencies and has an enhanced amplitude. The results are discussed in light of recent PTA hints for gravitational waves.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Simone Blasi, Ryusuk Jinno, Thomas Konstandin, Henrique Rubira, Isak Stomberg
Summary: We discuss the gravitational wave spectrum produced by first-order phase transitions seeded by domain wall networks. This setup is important for many two-step phase transitions, as seen in the singlet extension of the standard model, for example. When the correlation length of the domain wall network is larger than the typical bubble size, this setup leads to a gravitational wave signal that is shifted to lower frequencies and with an enhanced amplitude compared to homogeneous phase transitions without domain walls.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Luke Hart, Jens Chluba
Summary: The cosmological recombination radiation (CRR) is a spectral distortion signal from the early Universe that can probe physical phenomena in the pre-recombination era. We study the effects of early dark energy models and varying electromagnetic fundamental constants on CRR. We provide estimates on the sensitivity of future spectrometers to these effects and suggest that a combination with Planck data is promising.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Ariel Megevand, Federico Agustin Membiela
Summary: The study presents a general method for computing the gravitational radiation generated by the motion of bubble walls or thin fluid shells in cosmological phase transitions. The method is applied to different wall kinematics, deriving general expressions for bubble collision mechanisms and considering deformations from spherical bubble shapes. The study calculates the gravitational wave spectrum for a specific model of deformations on a definite size scale, resulting in a peak different from that of the bubble collision mechanism.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Jaume Garriga, Nikolaos Triantafyllou
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2019)
Article
Astronomy & Astrophysics
Vicente Atal, Jaume Garriga, Airam Marcos-Caballero
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2019)
Article
Astronomy & Astrophysics
Yu-Tong Wang, Jun Zhang, Yun-Song Piao
Article
Astronomy & Astrophysics
Vicente Atal, Judith Cid, Albert Escriva, Jaume Garriga
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2020)
Article
Physics, Multidisciplinary
Sebastian Garcia-Saenz, Aaron Held, Jun Zhang
Summary: The study reveals that perturbations of nonminimally coupled vector fields can destabilize black holes and stars in general relativity. Specifically, black holes with sufficiently small mass and stars with sufficiently high density may experience ghost- or gradient-type instabilities. This has implications for low-scale theories of dark energy and ultralight dark matter scenarios.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Multidisciplinary
Yiqi Xie, Jun Zhang, Hector O. Silva, Claudia de Rham, Helvi Witek, Nicolas Yunes
Summary: In general theories of gravity, the spacetime of a stationary, axisymmetric, and asymptotically flat solution must be circular if the solution can be perturbatively obtained from a solution in the general relativity limit. This result applies to a wide range of gravitational theories including arbitrary scalars and vectors, with nonstandard kinetic terms and nonminimal couplings to gravity treated perturbatively.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Multidisciplinary
Jun Zhang, Zhenwei Lyu, Junwu Huang, Matthew C. Johnson, Laura Sagunski, Mairi Sakellariadou, Huan Yang
Summary: A search for light axions sourced by neutron stars by analyzing gravitational waves from binary neutron star inspiral GW170817 did not yield any evidence of axions. This null result allowed for constraints to be imposed on axions with masses below 10(-11) eV.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Multidisciplinary
Claudia de Rham, Andrew J. Tolley, Jun Zhang
Summary: In this article, we investigate the effective field theory of gravity around black holes and find that the coefficients of the dimension-8 operators are tightly constrained by causality considerations. These constraints are more stringent than previously derived causality and positivity bounds, suggesting that the effects of a single dimension-8 operator cannot be observed while maintaining causality. We also identify the regime where the generic dimension-8 and lower order operators can potentially be observable while preserving causality.
PHYSICAL REVIEW LETTERS
(2022)
Article
Astronomy & Astrophysics
Huan Yang, Jun Zhang
Summary: It has been suggested that the spectrum of quasinormal modes of rotating black holes is unstable against additional potential terms in the perturbation equation, as the operator associated with the equation is non-self-adjoint. A bilinear form has been constructed previously to allow a perturbation analysis of the spectrum. It is necessary to study the stability of previous mode analysis results to reveal their susceptibility to energetically infinitesimal perturbations.
Article
Astronomy & Astrophysics
Aaron Held, Jun Zhang
Summary: We study the stability of two branches of spherically symmetric black holes in quadratic gravity and find a long-wavelength instability in both cases. This instability occurs below a critical horizon radius where the two black-hole branches intersect, indicating a lower bound on the horizon radius for such black holes in quadratic gravity imposed by classical perturbations.
Article
Astronomy & Astrophysics
Claudia de Rham, Jeremie Francfort, Jun Zhang
Article
Astronomy & Astrophysics
Jun Zhang, Huan Yang
Article
Astronomy & Astrophysics
Claudia de Rham, Jun Zhang
Article
Astronomy & Astrophysics
Jun Zhang, Huan Yang
Article
Astronomy & Astrophysics
Junwu Huang, Matthew C. Johnson, Laura Sagunski, Mairi Sakellariadou, Jun Zhang