Article
Physics, Multidisciplinary
Daniel G. Figueroa, Adrien Florio, Toby Opferkuch, Ben A. Stefanek
Summary: This paper investigates the important implications of scalar fields with non-minimal gravitational interactions for the physics of the early universe. A procedure is proposed to solve the dynamics of non-minimally coupled scalar fields directly in the Jordan frame, where the non-minimal couplings are explicitly maintained. The algorithm can be applied to lattice simulations that include minimally coupled fields and an arbitrary number of non-minimally coupled scalars, allowing for fully inhomogeneous and nonlinear dynamics and the domination of non-minimally coupled species in the expansion of the universe. As an example, geometric preheating with a non-minimally coupled scalar spectator field during the oscillations of the inflaton after inflation is studied.
Article
Astronomy & Astrophysics
Gilles Buldgen, Marco Drewes, Jin U. Kang, Ui Ri Mun
Summary: We present a general method to obtain an effective Markovian quantum kinetic equation for a slowly evolving scalar field in an adiabatically evolving background. The method requires minimal assumptions about the field's interactions and the composition of the background, as long as certain conditions regarding the coupling constants, time scales, and field derivatives are satisfied. The resulting equation of motion is expressed in terms of an effective potential and friction coefficients.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Steffen Gielen, Axel Polaczek
Summary: The author extends the construction of Hamiltonian group field theory to models with multiple scalar matter fields, finding that the effective cosmological dynamics reduce to the Friedmann dynamics of general relativity with multiple scalar fields in the limit of large volume. At high energy, corrections to the classical Friedmann equations are found, leading to generic singularity resolution by a bounce. Additionally, the effective cosmological dynamics treat the clock field and other matter fields differently for generic initial conditions, in disagreement with the Friedmann dynamics of general relativity.
Article
Astronomy & Astrophysics
Rafael Hernandez-Jimenez, Claudia Moreno
Summary: Starting with the Lagrangian formulation of General Relativity, this study investigates the production of spacetime waves caused by a geometric boundary term of a closed extended manifold. The research explores two scenarios, Cold Inflation and Warm Inflation, and finds that scalar modes oscillate within the horizon and become constant after crossing the horizon, while radiation reduces their amplitudes. The tensor sector exhibits irregular behavior due to abrupt growth as it crosses the horizon, making it difficult to observe.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Particles & Fields
Smaragda Lola, Andreas Lymperis, Emmanuel N. Saridakis
Summary: By applying deformed-steepness exponential potentials, we revisit inflation with non-canonical scalar fields and find that this scenario shows remarkable agreement with observational results, with significant advantages in describing correlations between model parameters. This combination of observational efficiency and theoretical justification makes it a good candidate for inflation description.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Yong Tang, Yue-Liang Wu
Summary: The paper investigates multiple scalar fields coupled nonminimally to gravity, utilizing conformal transformation to bring the theory into the Einstein frame. It explores under what conditions the theories can be transformed to the quasicanonical form and presents solutions that may be useful for future phenomenological model building. The study also finds that conformal flatness can be achieved in some modified gravity theories like the Starobinsky model.
Article
Astronomy & Astrophysics
Nina K. Stein, William H. Kinney
Summary: We have constructed a family of simple single-field inflation models that are consistent with Planck/BICEP Keck bounds. These models have a small tensor amplitude and no running of the scalar spectral index. The construction involves a constant-roll hilltop inflaton potential, with the end of inflation being a free parameter induced by dominant higher-order operators. This construction directly demonstrates that there is no lower bound on the tensor/scalar ratio for simple single-field inflation models.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
F. B. M. dos Santos, R. Silva
Summary: In this study, we revisit the Witten-O'Raifeartaigh model of inflation and find that a small coupling has better predictive power for inflationary parameters. The presence of a non-zero coupling allows for a larger range of mass scale, which enables a low tensor-to-scalar ratio. We also establish constraints imposed by a subsequent reheating era, which restrict the possible values of the n(s) and r parameters.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Jose Ademir Sales Lima, Pedro Eleuterio Mendonca Almeida
Summary: This paper explores a smooth dynamic evolution from an initial unstable de Sitter stage to the standard radiation phase using a dominant noncanonical scalar field, showing that the remaining potential energy density is stored in the kinetic part of the field at the end of the vacuum decaying process. The resulting noncanonical cosmology can be interpreted as a dynamical Lambda-model, with the spontaneous decaying process into radiation possibly being the origin of the primeval thermal bath.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2021)
Article
Astronomy & Astrophysics
Oleg Lebedev
Summary: Stable scalars can be abundantly produced in the Early Universe even without coupling to other fields. The production and mass scale of these scalars during and after (high scale) inflation are studied, leading to strong constraints. Quantum gravity-induced Planck-suppressed operators significantly affect the abundance of dark matter relics, often resulting in overproduction unless the corresponding Wilson coefficients are very small. The uncontrollable nature of these effects without a quantum gravity theory questions the predictability of many non-thermal dark matter models and has potential implications for string theory constructions with abundant scalar fields.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Physics, Particles & Fields
Arko Bhaumik, Soumitra SenGupta
Summary: The study demonstrates that it is possible to stabilize two distinct moduli simultaneously in a model with nested warping, by introducing an effective 4D moduli potential. This mechanism offers a resolution to the hierarchy problem in the Standard Model.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
M. Shahalam, Kuralay Yesmakhanova, Zhanar Umurzakhova
Summary: In this paper, the dynamics of pre-inflation with Hilltop potential in the framework of loop quantum cosmology is investigated. Two categories of initial conditions for the inflaton field at the quantum bounce, dominated by kinetic energy and potential energy respectively, are studied. Numerical calculations show that physically viable initial values can generate the desired slow-roll inflation and sufficient number of e-folds. Phase space analysis is also conducted for the Hilltop potential.
GENERAL RELATIVITY AND GRAVITATION
(2023)
Article
Physics, Particles & Fields
Saikat Chakraborty, Esteban Gonzalez, Genly Leon, Bin Wang
Summary: This paper studies a cosmological model inspired by axionic matter, involving two scalar fields interacting through a added potential term. By introducing new variables and a dimensionless time scale, the resulting dynamics are explored. The analysis of oscillations using methods from the theory of averaging nonlinear systems is motivated by difficulties in standard approaches, ultimately proving the consistency of time-dependent systems and their time-averaged counterparts in late-time dynamics.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Astrid Eichhorn, Martin Pauly
Summary: The study indicates that quantum gravitational fluctuations may drive scalar potentials towards flatness, asymptotic safety can rule out parameter space in scalar dark matter models, and nonminimal Higgs-curvature coupling may be constrained.
Article
Astronomy & Astrophysics
Anne-Christine Davis, Scott Melville
Summary: The study focuses on the application of low-energy effective field theories containing a light scalar field in cosmology, identifying smooth resummation of classical non-linearities for achieving screening mechanisms and analyzing the range of interaction couplings and positivity bounds. The results will guide future searches for UV complete models which exhibit screening of fifth forces in the IR.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Josu C. Aurrekoetxea, Thomas Helfer, Eugene A. Lim
CLASSICAL AND QUANTUM GRAVITY
(2020)
Article
Astronomy & Astrophysics
Low Lerh Feng, Shaun Hotchkiss, Richard Easther
Summary: The study suggests that in a multi-dimensional Gaussian random potential, the proportion of positive minima decreases super-exponentially with N. Eigenvalues of the Hessian matrices reveal that the flattest approaches to typical minima become flatter with increasing N, while the ratio of slopes also increases with N.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Review
Physics, Particles & Fields
K. G. Arun, Enis Belgacem, Robert Benkel, Laura Bernard, Emanuele Berti, Gianfranco Bertone, Marc Besancon, Diego Blas, Christian G. Bohmer, Richard Brito, Gianluca Calcagni, Alejandro Cardenas-Avendano, Katy Clough, Marco Crisostomi, Valerio De Luca, Daniela Doneva, Stephanie Escoffier, Jose Maria Ezquiaga, Pedro G. Ferreira, Pierre Fleury, Stefano Foffa, Gabriele Franciolini, Noemi Frusciante, Juan Garcia-Bellido, Carlos Herdeiro, Thomas Hertog, Tanja Hinderer, Philippe Jetzer, Lucas Lombriser, Elisa Maggio, Michele Maggiore, Michele Mancarella, Andrea Maselli, Sourabh Nampalliwar, David Nichols, Maria Okounkova, Paolo Pani, Vasileios Paschalidis, Alvise Raccanelli, Lisa Randall, Sebastien Renaux-Petel, Antonio Riotto, Milton Ruiz, Alexander Saffer, Mairi Sakellariadou, Ippocratis D. Saltas, B. S. Sathyaprakash, Lijing Shao, Carlos F. Sopuerta, Thomas P. Sotiriou, Nikolaos Stergioulas, Nicola Tamanini, Filippo Vernizzi, Helvi Witek, Kinwah Wu, Kent Yagi, Stoytcho Yazadjiev, Nicolas Yunes, Miguel Zilhao, Niayesh Afshordi, Marie-Christine Angonin, Vishal Baibhav, Enrico Barausse, Tiago Barreiro, Nicola Bartolo, Nicola Bellomo, Ido Ben-Dayan, Eric A. Bergshoeff, Sebastiano Bernuzzi, Daniele Bertacca, Swetha Bhagwat, Beatrice Bonga, Lior M. Burko, Geoffrey Compere, Giulia Cusin, Antonio da Silva, Saurya Das, Claudia de Rham, Kyriakos Destounis, Ema Dimastrogiovanni, Francisco Duque, Richard Easther, Hontas Farmer, Matteo Fasiello, Stanislav Fisenko, Kwinten Fransen, Jorg Frauendiener, Jonathan Gair, Laszlo Arpad Gergely, Davide Gerosa, Leonardo Gualtieri, Wen-Biao Han, Aurelien Hees, Thomas Helfer, Jorg Hennig, Alexander C. Jenkins, Eric Kajfasz, Nemanja Kaloper, Vladimir Karas, Bradley J. Kavanagh, Sergei A. Klioner, Savvas M. Koushiappas, Macarena Lagos, Christophe Le Poncin-Lafitte, Francisco S. N. Lobo, Charalampos Markakis, Prado Martin-Moruno, C. J. A. P. Martins, Sabino Matarrese, Daniel R. Mayerson, Jose P. Mimoso, Johannes Noller, Nelson J. Nunes, Roberto Oliveri, Giorgio Orlando, George Pappas, Igor Pikovski, Luigi Pilo, Geraint Pratten, Tomislav Prokopec, Hong Qi, Saeed Rastgoo, Angelo Ricciardone, Rocco Rollo, Diego Rubiera-Garcia, Olga Sergijenko, Stuart Shapiro, Deirdre Shoemaker, Alessandro Spallicci, Oleksandr Stashko, Leo C. Stein, Gianmassimo Tasinato, Andrew J. Tolley, Elias C. Vagenas, Stefan Vandoren, Daniele Vernieri, Rodrigo Vicente, Toby Wiseman, Valery Zhdanov, Miguel Zumalacarregui
Summary: This white paper summarizes the importance of LISA in the field of fundamental physics and discusses future research directions and connections with other working groups.
LIVING REVIEWS IN RELATIVITY
(2022)
Article
Astronomy & Astrophysics
Lerh Feng Low, Richard Easther, Shaun Hotchkiss
Summary: Random, multifield functions can set generic expectations for landscape-style cosmologies. By considering the inflationary implications of a landscape defined by a Gaussian random function, it is shown that the key properties of this landscape depend only on its dimensionality and a single parameter, and the fraction of saddles supporting inflation can be computed, allowing the identification of scenarios resembling our universe.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Benedict Bahr-Kalus, David Parkinson, Richard Easther
Summary: The ability to test and constrain theories of cosmic inflation will greatly improve in the next decade. Key data sources include cosmic microwave background (CMB) measurements and observations of matter distribution at low-redshift. A positive detection of a CMB B-mode consistent with a primordial stochastic gravitational wave background (SGWB) is considered strong evidence for inflation, but a null result does not exclude it. This study forecasts the precision with which the spectral index n(s) and the running alpha(s) can be constrained by current and planned observations, providing informative constraints on the inflationary parameter space if the SGWB remains undetected.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Review
Physics, Particles & Fields
Pierre Auclair, David Bacon, Tessa Baker, Tiago Barreiro, Nicola Bartolo, Enis Belgacem, Nicola Bellomo, Ido Ben-Dayan, Daniele Bertacca, Marc Besancon, Jose J. Blanco-Pillado, Diego Blas, Guillaume Boileau, Gianluca Calcagni, Robert Caldwell, Chiara Caprini, Carmelita Carbone, Chia-Feng Chang, Hsin-Yu Chen, Nelson Christensen, Sebastien Clesse, Denis Comelli, Giuseppe Congedo, Carlo Contaldi, Marco Crisostomi, Djuna Croon, Yanou Cui, Giulia Cusin, Daniel Cutting, Charles Dalang, Valerio De Luca, Walter Del Pozzo, Vincent Desjacques, Emanuela Dimastrogiovanni, Glauber C. Dorsch, Jose Maria Ezquiaga, Matteo Fasiello, Daniel G. Figueroa, Raphael Flauger, Gabriele Franciolini, Noemi Frusciante, Jacopo Fumagalli, Juan Garcia-Bellido, Oliver Gould, Daniel Holz, Laura Iacconi, Rajeev Kumar Jain, Alexander C. Jenkins, Ryusuke Jinno, Cristian Joana, Nikolaos Karnesis, Thomas Konstandin, Kazuya Koyama, Jonathan Kozaczuk, Sachiko Kuroyanagi, Danny Laghi, Marek Lewicki, Lucas Lombriser, Eric Madge, Michele Maggiore, Ameek Malhotra, Michele Mancarella, Vuk Mandic, Alberto Mangiagli, Sabino Matarrese, Anupam Mazumdar, Suvodip Mukherjee, Ilia Musco, Germano Nardini, Jose Miguel No, Theodoros Papanikolaou, Marco Peloso, Mauro Pieroni, Luigi Pilo, Alvise Raccanelli, Sebastien Renaux-Petel, Arianna I. Renzini, Angelo Ricciardone, Antonio Riotto, Joseph D. Romano, Rocco Rollo, Alberto Roper Pol, Ester Ruiz Morales, Mairi Sakellariadou, Ippocratis D. Saltas, Marco Scalisi, Kai Schmitz, Pedro Schwaller, Olga Sergijenko, Geraldine Servant, Peera Simakachorn, Lorenzo Sorbo, Lara Sousa, Lorenzo Speri, Daniele A. Steer, Nicola Tamanini, Gianmassimo Tasinato, Jesus Torrado, Caner Unal, Vincent Vennin, Daniele Vernieri, Filippo Vernizzi, Marta Volonteri, Jeremy M. Wachter, David Wands, Lukas T. Witkowski, Miguel Zumalacarregui, James Annis, Feanor Reuben Ares, Pedro P. Avelino, Anastasios Avgoustidis, Enrico Barausse, Alexander Bonilla, Camille Bonvin, Pasquale Bosso, Matteo Calabrese, Mesut Caliskan, Jose A. R. Cembranos, Mikael Chala, David Chernoff, Katy Clough, Alexander Criswell, Saurya Das, Antonio da Silva, Pratika Dayal, Valerie Domcke, Ruth Durrer, Richard Easther, Stephanie Escoffier, Sandrine Ferrans, Chris Fryer, Jonathan Gair, Chris Gordon, Martin Hendry, Mark Hindmarsh, Deanna C. Hooper, Eric Kajfasz, Joachim Kopp, Savvas M. Koushiappas, Utkarsh Kumar, Martin Kunz, Macarena Lagos, Marc Lilley, Joanes Lizarraga, Francisco S. N. Lobo, Azadeh Maleknejad, C. J. A. P. Martins, P. Daniel Meerburg, Renate Meyer, Jose Pedro Mimoso, Savvas Nesseris, Nelson Nunes, Vasilis Oikonomou, Giorgio Orlando, Ogan Ozsoy, Fabio Pacucci, Antonella Palmese, Antoine Petiteau, Lucas Pinol, Simon Portegies Zwart, Geraint Pratten, Tomislav Prokopec, John Quenby, Saeed Rastgoo, Diederik Roest, Kari Rummukainen, Carlo Schimd, Aurelia Secroun, Alberto Sesana, Carlos F. Sopuerta, Ismael Tereno, Andrew Tolley, Jon Urrestilla, Elias C. Vagenas, Jorinde van de Vis, Rien van de Weygaert, Barry Wardell, David J. Weir, Graham White, Bogumila Swiezewska, Valery I. Zhdanov
Summary: This publication provides an overview of the latest advancements in LISA cosmology, including theory and methods, and identifies new opportunities to probe the universe using gravitational-wave observations by LISA.
LIVING REVIEWS IN RELATIVITY
(2023)
Article
Astronomy & Astrophysics
J. Luna Zagorac, Emily Kendall, Nikhil Padmanabhan, Richard Easther
Summary: Ultralight dark matter (ULDM) is a dark matter candidate with a small particle mass. ULDM halos consist of a solitonic core and an NFW-like skirt. By simulating soliton mergers, we studied the core-halo mass relation and found no universal relationship for ULDM.
Article
Astronomy & Astrophysics
Mateja Gosenca, Andrew Eberhardt, Yourong Wang, Benedikt Eggemeier, Emily Kendall, J. Luna Zagorac, Richard Easther
Summary: Ultralight dark matter (ULDM) is usually assumed to be a single scalar field, but we explore the possibility that it consists of N light scalar fields with only gravitational interactions, which is more consistent with the underlying particle physics motivations for these scenarios. In multifield simulations, we find that the amplitude of the total density fluctuations inside a ULDM halo decreases as 1/sqrt(N) and the fields do not significantly correlate over cosmological timescales. Smoother halos heat stellar orbits less efficiently, weakening the observational constraints on the field mass.
Article
Astronomy & Astrophysics
Benedikt Eggemeier, Jens C. Niemeyer, Karsten Jedamzik, Richard Easther
Summary: After inflation, the early Universe may undergo a phase dominated by matter supported by oscillating inflaton condensate. Fluctuations in the condensate can collapse to form inflaton halos which source gravitational waves. We conducted N-body simulations to study the growth and interaction of these structures and calculate the resulting gravitational wave emission. Using a semianalytic formalism, we infer the spectrum for scenarios where the matter-dominated phase transitions to a thermalized universe at temperatures as low as 100 MeV.
Article
Astronomy & Astrophysics
Richard Easther, Benedict Bahr-Kalus, David Parkinson
Summary: Inflationary cosmology suggests that the early Universe underwent accelerated expansion, leading to density perturbations and gravitational waves. Researchers found that higher derivatives of the inflaton potential play a crucial role in the scale dependence of the density perturbation spectrum. If future experiments cannot detect a gravitational wave background, the running will be detectable up to the third order of the slow-roll expansion.
Article
Astronomy & Astrophysics
J. Luna Zagorac, Isabel Sands, Nikhil Padmanabhan, Richard Easther
Summary: This study investigates the dynamical evolution of perturbations to the spherically symmetric soliton in self-gravitating quantum matter. The study finds that the eigenstates of the Schr??dinger equation qualitatively capture the properties seen in full ultralight dark matter (ULDM) simulations. Additionally, the study shows that the time evolution of the gravitational potential and its impact on the perturbations can be well-described using time-dependent perturbation theory.
Article
Astronomy & Astrophysics
Yourong Wang, Richard Easther
Summary: In this study, we simulated the gravitational dynamics between a massive object and ultralight/fuzzy dark matter. The results showed gravitational collapse induced by a moving mass in a uniform medium, as well as coherent breathing modes in the dark matter caused by a large moving point mass.
Article
Astronomy & Astrophysics
Benedikt Eggemeier, Bodo Schwabe, Jens C. Niemeyer, Richard Easther
Summary: Researchers have found through simulations and calculations that inflaton fields in the early universe can collapse into inflaton stars, which can potentially form primordial black holes.
Article
Astronomy & Astrophysics
Benedikt Eggemeier, Jens C. Niemeyer, Richard Easther
Summary: Research suggests that the early Universe goes through a matter-dominated expansion phase after inflation, potentially leading to subhorizon density perturbations collapsing into structures and forming inflaton halos and other celestial bodies. Simulation results show a strong analogy between this process and structure formation in the present-day Universe, impacting the dynamics and evolution of the cosmos.
Article
Astronomy & Astrophysics
Peter Adshead, Niayesh Afshordi, Emanuela Dimastrogiovanni, Matteo Fasiello, Eugene A. Lim, Gianmassimo Tasinato
Summary: Characterizing the physical properties of the SGWB, focusing on anisotropies, can be an effective probe of early universe physics by cross correlating with the CMB. This can provide a smoking gun for primordial SGWB anisotropies.