Sarunas Verner
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View article: Constraints on Attractor Models of Inflation and Reheating from Planck, BICEP/Keck, ACT DR6, and SPT-3G Data
Constraints on Attractor Models of Inflation and Reheating from Planck, BICEP/Keck, ACT DR6, and SPT-3G Data Open
We analyze the latest cosmic microwave background (CMB) constraints on the scalar spectral index $n_s$ and tensor-to-scalar ratio $r$ from Planck 2018, BICEP/Keck 2018, the Atacama Cosmology Telescope Data Release 6 (ACT DR6), and the Sout…
View article: Erratum: New Method for the Astrometric Direct Detection of Ultralight Dark Matter [Phys. Rev. Lett. <b>134</b>, 111003 (2025)]
Erratum: New Method for the Astrometric Direct Detection of Ultralight Dark Matter [Phys. Rev. Lett. <b>134</b>, 111003 (2025)] Open
This corrects the article DOI: 10.1103/PhysRevLett.134.111003.
View article: Scalar field fluctuations and the production of dark matter
Scalar field fluctuations and the production of dark matter Open
One of the simplest possible candidates for dark matter is a stable scalar singlet beyond the Standard Model. If its mass is below the Hubble scale during inflation, long-wavelength modes of this scalar will be excited during inflation, an…
View article: Gravitational Waves from Spectator Scalar Fields
Gravitational Waves from Spectator Scalar Fields Open
We propose a novel mechanism for gravitational wave (GW) production sourced by spectator scalar fields during inflation. These fields, while not driving cosmic expansion, generate blue-tilted isocurvature fluctuations that naturally satisf…
View article: The Electroweak Sphaleron Revisited: II. Study of Decay Dynamics
The Electroweak Sphaleron Revisited: II. Study of Decay Dynamics Open
We present a comprehensive analysis of electroweak sphaleron decay dynamics, employing both analytical techniques and high-resolution numerical simulations. Using a spherically symmetric ansatz, we reformulate the system as a $(1+1)$-dimen…
View article: Nonminimal superheavy dark matter
Nonminimal superheavy dark matter Open
We investigate the gravitational production of superheavy scalar fields with nonminimal coupling during and after inflation. Using the mode function solution in a de Sitter background, we derive analytical approximations and apply the stee…
View article: New Method for the Astrometric Direct Detection of Ultralight Dark Matter
New Method for the Astrometric Direct Detection of Ultralight Dark Matter Open
Ultralight dark matter induces time-dependent perturbations in the spacetime metric, enabling its . In this Letter, we propose using astrometry to detect dark matter. After reviewing the calculation of the metric in the presence of scalar …
View article: Inflaton production of scalar dark matter through fluctuations and scattering
Inflaton production of scalar dark matter through fluctuations and scattering Open
We study the effects on particle production of a Planck-suppressed coupling between the inflaton and a scalar dark matter candidate, χ. In the absence of this coupling the dominant source for the relic density of χ is the long wavelength m…
View article: Gravitational production of heavy particles during and after inflation
Gravitational production of heavy particles during and after inflation Open
A bstract We investigate the gravitational production of a scalar field χ with a mass exceeding the Hubble scale during inflation m χ ≳ H I , employing both analytical and numerical approaches. We demonstrate that the steepest descent meth…
View article: Nonminimal Superheavy Dark Matter
Nonminimal Superheavy Dark Matter Open
We investigate the gravitational production of superheavy scalar fields with nonminimal coupling during and after inflation. We derive analytical approximations using the mode function solution in a de Sitter background and also apply the …
View article: Exploring the truth and beauty of theory landscapes with machine learning
Exploring the truth and beauty of theory landscapes with machine learning Open
View article: Inflaton Production of Scalar Dark Matter through Fluctuations and Scattering
Inflaton Production of Scalar Dark Matter through Fluctuations and Scattering Open
We study the effects on particle production of a Planck-suppressed coupling between the inflaton and a scalar dark matter candidate, $χ$. In the absence of this coupling, the dominant source for the relic density of $χ$ is the long wavelen…
View article: Astrometric Detection of Ultralight Dark Matter
Astrometric Detection of Ultralight Dark Matter Open
Ultralight dark matter induces time-dependent perturbations in the spacetime metric, enabling its gravitational direct detection. In this work, we propose using astrometry to detect dark matter. After reviewing the calculation of the metri…
View article: The role of vectors in reheating
The role of vectors in reheating Open
We explore various aspects concerning the role of vector bosons during the reheating process. Generally, reheating occurs during the period of oscillations of the inflaton condensate and the evolution of the radiation bath depends on the i…
View article: Inflaton Decay in No-Scale Supergravity and Starobinsky-like Models
Inflaton Decay in No-Scale Supergravity and Starobinsky-like Models Open
We consider the decay of the inflaton in Starobinsky-like models arising from either an R+R2 theory of gravity or N=1 no-scale supergravity models. If Standard Model matter is simply introduced to the R+R2 theory, the inflaton (which appea…
View article: Gravitational Production of Heavy Particles during and after Inflation
Gravitational Production of Heavy Particles during and after Inflation Open
We investigate the gravitational production of a scalar field $χ$ with a mass exceeding the Hubble scale during inflation $m_χ\gtrsim H_I$, employing both analytical and numerical approaches. We demonstrate that the steepest descent method…
View article: Testing the scalar weak gravity conjecture in no-scale supergravity
Testing the scalar weak gravity conjecture in no-scale supergravity Open
A bstract We explore possible extensions of the Weak Gravity Conjecture (WGC) to scalar field theories. To avoid charged black hole remnants, the WGC requires the existence of a particle with a mass m ≤ gqM P , with charge q and U(1) gauge…
View article: Inflaton decay in No-Scale Supergravity and Starobinsky-like models
Inflaton decay in No-Scale Supergravity and Starobinsky-like models Open
We consider the decay of the inflaton in Starobinsky-like models arising from either an $R+R^2$ theory of gravity or $N=1$ no-scale supergravity models. If Standard Model matter is simply introduced to the $R + R^2$ theory, the inflaton (w…
View article: Cosmological collider signatures of Higgs-R<sup>2</sup> inflation
Cosmological collider signatures of Higgs-R<sup>2</sup> inflation Open
We study the cosmological collider signatures in the Higgs- R 2 inflation model. We consider two distinct types of signals: one originating from the inflaton coupling to Standard Model fermions and gauge bosons, and another arising from th…
View article: Exploring the Truth and Beauty of Theory Landscapes with Machine Learning
Exploring the Truth and Beauty of Theory Landscapes with Machine Learning Open
Theoretical physicists describe nature by i) building a theory model and ii) determining the model parameters. The latter step involves the dual aspect of both fitting to the existing experimental data and satisfying abstract criteria like…
View article: Gravitational production of spin-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mn>3</mml:mn><mml:mo>/</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:math> particles during reheating
Gravitational production of spin- particles during reheating Open
We compute the density of a spin-$\\frac{3}{2}$ particle, the raritron, produced at the end of inflation due to gravitational interactions. We consider a background inflaton condensate as the source of this production, mediated by the exch…
View article: New window into gravitationally produced scalar dark matter
New window into gravitationally produced scalar dark matter Open
Conventional scenarios of purely gravitationally produced dark matter with masses below the Hubble parameter at the end of inflation are in tension with cosmic microwave background (CMB) constraints on the isocurvature power spectrum. We e…
View article: The Role of Vectors in Reheating
The Role of Vectors in Reheating Open
We explore various aspects concerning the role of vector bosons during the reheating process. Generally, reheating occurs during the period of oscillations of the inflaton condensate and the evolution of the radiation bath depends on the i…
View article: Identifying the group-theoretic structure of machine-learned symmetries
Identifying the group-theoretic structure of machine-learned symmetries Open
View article: Seeking Truth and Beauty in Flavor Physics with Machine Learning
Seeking Truth and Beauty in Flavor Physics with Machine Learning Open
The discovery process of building new theoretical physics models involves the dual aspect of both fitting to the existing experimental data and satisfying abstract theorists' criteria like beauty, naturalness, etc. We design loss functions…
View article: Supergravity scattering amplitudes
Supergravity scattering amplitudes Open
Supergravity theories with nonminimal Kähler potentials are characterized by a nontrivial field space manifold with corresponding nontrivial kinetic terms. The scattering amplitudes in these theories can be calculated at fixed background f…
View article: Accelerated discovery of machine-learned symmetries: Deriving the exceptional Lie groups G2, F4 and E6
Accelerated discovery of machine-learned symmetries: Deriving the exceptional Lie groups G2, F4 and E6 Open
Recent work has applied supervised deep learning to derive continuous symmetry transformations that preserve the data labels and to obtain the corresponding algebras of symmetry generators. This letter introduces two improved algorithms th…
View article: Gravitational Production of Spin-3/2 Particles During Reheating
Gravitational Production of Spin-3/2 Particles During Reheating Open
We compute the density of a spin-$\frac32$ particle, the raritron, produced at the end of inflation due to gravitational interactions. We consider a background inflaton condensate as the source of this production, mediated by the exchange …
View article: Cosmological Collider Signatures of Higgs-$R^2$ Inflation
Cosmological Collider Signatures of Higgs-$R^2$ Inflation Open
We study the cosmological collider signatures in the Higgs-$R^2$ inflation model. We consider two distinct types of signals: one originating from the inflaton coupling to Standard Model fermions and gauge bosons, and another arising from t…
View article: Identifying the Group-Theoretic Structure of Machine-Learned Symmetries
Identifying the Group-Theoretic Structure of Machine-Learned Symmetries Open
Deep learning was recently successfully used in deriving symmetry transformations that preserve important physics quantities. Being completely agnostic, these techniques postpone the identification of the discovered symmetries to a later s…