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
Min-Seok Seo
Summary: This paper discusses the influence of quantum fluctuations and density fluctuations on black hole production in inflation. It proposes the equivalence between the no eternal inflation condition and the condition that radiation density fluctuations are not sufficient to produce black holes. It also highlights that the information paradox does not arise when the radiation emitted by the horizon does not produce black holes.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Orfeu Bertolami, Paulo M. Sa
Summary: Multi-field cold inflation models are usually at odds with the swampland conjectures in string theory, but can be reconciled in the strong dissipative regime of warm inflation.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Sergei Ketov
Summary: A novel gravitational theory, inspired by string theory, is proposed in four spacetime dimensions. This theory combines the modified (R+alpha R-2) gravity motivated by the Starobinsky inflation with the Bel-Robinson-tensor-squared correction from superstrings/M-theory compactified down to four dimensions. The origin of this theory from higher dimensions is also revealed. The proposed theory, called the Starobinsky-Bel-Robinson action, has only two free parameters, making it suitable for verifiable applications in black hole physics, cosmological inflation, and Hawking radiation.
Article
Astronomy & Astrophysics
Vikas Aragam, Roberta Chiovoloni, Sonia Paban, Robert Rosati, Ivonne Zavala
Summary: Strongly non-geodesic, or rapidly turning trajectories in multifield inflation, have recently gained significant attention from both theoretical and phenomenological perspectives. Most existing models with large turning rates are formulated within the framework of effective field theories. This paper investigates rapid-turn inflation in supergravity as an initial step towards understanding them in the context of string theory. The research reveals that large turning rates can be achieved in a wide range of models, but at the expense of high field space curvature. The models satisfy the de Sitter swampland conjecture along the inflationary trajectory, but the high curvatures highlight the challenges in obtaining rapid-turn inflation in realistic string-theoretical models.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Omer Guleryuz
Summary: In this work, an effective field theory for string inflation with spontaneously broken supersymmetry is presented, without generating any supersymmetric anti-de Sitter vacua. The analysis of nilpotent superfields effectively captures the physics of anti-D3 branes and reveals a novel uplifting method by adding the same parameter as a complex contribution parallel to the decomposition of a superfield. With almost vanishing cosmological constant in the region where the inflationary attractors unify, the introduction of nilpotent superfields drastically extends the string landscape for the de Sitter (swampland) conjecture.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Kareem Marzouk, Alessandro Maraio, David Seery
Summary: In this study, we update predictions for observables in the "delicate" D3/(D3) over bar inflationary model on the conifold. Our analysis shows that the model can accurately forecast the amplitude of three-point correlations. The model generally follows Maldacena's single-field prediction, but in some cases, the bispectrum is dominated by effects from rapid switching between angular minima, resulting in larger amplitudes but with unacceptable spectral behavior.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Julian Freigang, Dieter Luest, Guo-En Nian, Marco Scalisi
Summary: This study examines the validity of the Swampland Distance Conjecture on prototype geometries of infinite distance limits of Calabi-Yau compactifications and finds that field trajectories leading to cosmic acceleration and featuring rapid turns near the boundary of the moduli space exist in the Swampland. This has significant implications for the realization and consistency of multi-field scenarios in string theory.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Anibal Faundez, Radouane Gannouji
Summary: We studied the existence and stability of Q-balls in noncanonical scalar field theories. We extended the Vakhitov-Kolokolov stability criterion to K-field theories and derived the condition for well-posed Cauchy problem of perturbations. We found that K,X > 0 and K,X + XK,XX > 0 are necessary but not sufficient conditions, and that perturbations define a strongly hyperbolic system if (K,X - 2002K,XX)(K,X + 2 omega 202K,X X) > 0. The noncanonical scalar field can lower the charge and energy of the Q-ball, improving its stability.
Article
Astronomy & Astrophysics
Khursid Alam, Koushik Dutta
Summary: This paper studies how the effects of reheating can ease the problem of moduli destabilization. The associated time scale of producing the thermal bath allows for a larger initial field range to stabilize the field. Contrary to the usual notion, a larger initial field range is allowed for higher temperatures when the effective potential is of a run-away nature. This eases the moduli destabilization problem for heavy mass moduli. However, for low mass moduli, the allowed field range still violates the constraints of the cosmological moduli problem unless its initial abundance is suppressed.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Ugur Atli, Omer Guleryuz
Summary: This study introduces a bounded de Sitter conjecture for single-field slow-roll inflation theory, incorporating the concepts of supergravity methods, Kahler kinetic terms, and single-field slow-roll inflation parameters.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Physics, Multidisciplinary
Renata Kallosh, Andrei Linde, Timm Wrase, Yusuke Yamada
Summary: Sequestered inflation models are developed where inflation occurs along flat directions in supergravity models derived from type IIB string theory. By using flux potentials and nilpotent multiplets, the flat directions are lifted to phenomenological inflationary plateau potentials. The masses of heavy fields and the volume of extra dimensions change during inflation, but this does not affect the inflationary dynamics.
FORTSCHRITTE DER PHYSIK-PROGRESS OF PHYSICS
(2021)
Article
Astronomy & Astrophysics
Suddhasattwa Brahma, Robert Brandenberger, Ziwei Wang
Summary: The entanglement entropy of scalar perturbations due to gravitational non-linearities in a canonical, single-field ekpyrosis model was calculated in this study. By ensuring that the entanglement entropy remains subdominant to the thermal entropy generated during reheating, an upper bound on the energy scale of the bounce was obtained.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Miguel-Angel Sanchis-Lozano
Summary: We interpret the lack of large-angle temperature correlations and the even-odd parity imbalance observed in the cosmic microwave background as a possible stringy signal ultimately stemming from a composite inflaton field.
Article
Astronomy & Astrophysics
Michele Cicoli, Veronica Guidetti, Francesco Muia, Francisco G. Pedro, Gian Paolo Vacca
Summary: In type IIB fibre inflation models, it has been argued that the instability caused by tachyonic isocurvature perturbations is unphysical due to the use of ill-defined entropy variables. By employing the correct relative entropy perturbation, it has been demonstrated that axionic isocurvature perturbations decay during inflation and the dynamics becomes essentially single-field.
CLASSICAL AND QUANTUM GRAVITY
(2022)
Article
Astronomy & Astrophysics
Thomas C. Bachlechner, Mafalda Dias, Jonathan Frazer, Liam McAllister
Article
Physics, Particles & Fields
Thomas C. Bachlechner, Cody Long, Liam McAllister
JOURNAL OF HIGH ENERGY PHYSICS
(2015)
Article
Physics, Particles & Fields
Thomas C. Bachlechner, Cody Long, Liam McAllister
JOURNAL OF HIGH ENERGY PHYSICS
(2016)
Article
Astronomy & Astrophysics
Raphael Flauger, Liam McAllister, Eva Silverstein, Alexander Westphal
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2017)
Article
Physics, Particles & Fields
Cody Long, Liam McAllister, John Stout
JOURNAL OF HIGH ENERGY PHYSICS
(2017)
Article
Physics, Particles & Fields
Liam McAllister, Pedro Schwaller, Geraldine Servant, John Stout, Alexander Westphal
JOURNAL OF HIGH ENERGY PHYSICS
(2018)
Article
Astronomy & Astrophysics
Valentin Assassi, Daniel Baumann, Daniel Green, Liam McAllister
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2014)
Article
Physics, Particles & Fields
Cody Long, Liam McAllister, Paul McGuirk
JOURNAL OF HIGH ENERGY PHYSICS
(2014)
Article
Physics, Particles & Fields
Mehmet Demirtas, Cody Long, Liam McAllister, Mike Stillman
JOURNAL OF HIGH ENERGY PHYSICS
(2020)
Article
Physics, Multidisciplinary
Mehmet Demirtas, Manki Kim, Liam McAllister, Jakob Moritz
PHYSICAL REVIEW LETTERS
(2020)
Article
Physics, Particles & Fields
Mehmet Demirtas, Cody Long, Liam McAllister, Mike Stillman
JOURNAL OF HIGH ENERGY PHYSICS
(2020)
Article
Physics, Particles & Fields
Manki Kim, Liam McAllister
JOURNAL OF HIGH ENERGY PHYSICS
(2020)
Article
Physics, Multidisciplinary
Mehmet Demirtas, Manki Kim, Liam McAllister, Jakob Moritz, Andres Rios-Tascon
Summary: We present a supersymmetric vacuum in string theory with a vacuum energy magnitude smaller than 10^(-123) in Planck units. Our proposed mechanism generates a well-controlled exponential hierarchy by choosing appropriate quantized parameters in the superpotential. This approach offers a new perspective on the cosmological constant problem.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Particles & Fields
Shamit Kachru, Manki Kim, Liam McAllister, Max Zimet
Summary: By analyzing the interactions in ten-dimensional supergravity involving D7-branes and anti-D3-branes, it was shown that the equations of motion require the four-dimensional curvature to precisely match the values determined by the four-dimensional effective theory.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)