arXiv subjects

Sergei V. Ketov

Publications and source records attributed to Sergei V. Ketov.

At least 19 recordsLinked to original sources

arXiv2026

Higgsino dark matter in the Starobinsky supergravity with the MSSM in light of the LUX-ZEPLIN event

We realize a nearly pure higgsino dark matter candidate with mass of about 1 TeV in the Minimal Supersymmetric Standard Model coupled to the Starobinsky supergravity. The recent LUX-ZEPLIN 248 keV nuclear-recoil event has renewed interest in higgsino dark matter. In this framework, the particle spectrum, including the Higgs boson mass, the higgsino mass and its splitting, is connected to cosmic inflation observables via gravitational mediation of supersymmetry breaking and subsequent renormalization group evolution. We show that the Higgs boson mass predicted by the model agrees with the measured value within the quoted uncertainties for a broad range of bino-induced mass splittings. Wino-induced splitting leads to a Higgs mass several GeV higher and is therefore excluded.

hep-ph↗

arXiv2026

Higgs boson mass and thermal wino dark matter from Starobinsky supergravity with the MSSM

We propose a framework connecting cosmic microwave background (CMB) observables with high-energy particle phenomenology, based on Starobinsky supergravity coupled to the Minimal Supersymmetric Standard Model (MSSM). Cosmic inflation and supersymmetry (SUSY) breaking occur within the hidden sector emerging from Starobinsky supergravity. The inflationary scale sets the hidden-sector mass scale and, via gravitational mediation of SUSY breaking, the MSSM soft terms. The same hidden sector can also dynamically generate a high-scale $μ$ term. The resulting MSSM spectrum fixes the high-scale threshold corrections and the boundary conditions for the renormalisation-group (RG) evolution of the Higgs quartic coupling. Three-loop RG evolution of the Higgs quartic coupling gives a Higgs boson mass consistent with the measured value within the theoretical and experimental uncertainties, thereby linking the amplitude of primordial scalar perturbations to the Higgs boson mass. With conserved R-parity, the lightest supersymmetric particle is stable, and the minimal framework developed here points to a nearly pure neutral wino as the dark-matter (DM) candidate. In the thermal-relic scenario, the observed abundance selects a wino mass of about $3$ TeV. Recent gamma-ray analyses exclude it as the sole DM component, even for conservative cored Galactic profiles. Alternatives include a subdominant wino fraction or late entropy dilution. Its loop-induced spin-independent wino-nucleon scattering cross section lies below current LUX-ZEPLIN sensitivity but within reach of next-generation liquid-xenon detectors. Electroweak corrections generate a small charged-neutral wino mass splitting, producing a long-lived charged wino and disappearing-track signature. A future $100$ TeV proton collider can discover the corresponding pure-wino signal or exclude the scenario independently of its cosmological abundance.

hep-ph↗

arXiv2025

Single-field D-type inflation in the minimal supergravity in light of Planck-ACT-SPT data

The minimal supergravity framework is applied to a construction of new D-type single-field models of inflation in agreement with precision measurements of the cosmic microwave background radiation by Planck Collaboration, BICEP/Keck Collaboration, Atacama Cosmology Telescope and South Pole Telescope. The inflaton potential, the power spectrum of scalar perturbations, the cosmological observables and the reconstruction procedure can be very simple when using the e-folds as the running variable.

gr-qc↗

arXiv2025

$F$-term Multi-Field Inflation in Supergravity without Stabiliser Superfields

Realising $F$-term slow-roll inflation in supergravity is non-trivial due to the well-known $η$-problem. The common strategy to solve the problem is to impose a shift symmetry on the Kähler potential, but this often leads to a negative potential in the large-field regime. To avoid negative potentials, an additional superfield called the stabiliser is usually added with a desired interaction. An alternative mechanism in supergravity, avoiding the use of a stabiliser superfield, was earlier proposed by two of us in the setup with a single chiral superfield having inflaton and goldstino amongst its field components. In this work, we extend that alternative mechanism to multi-superfield models of inflation, thereby providing a generic framework for embedding a wide class of single- and multi-field inflation models into supergravity. We illustrate our approach by several concrete examples of multi-field inflation and clarify the conditions required to avoid tachyonic instabilities during multi-field evolution. Our proposal significantly broadens the theoretical landscape of $F$-term inflation models in supergravity.

hep-th↗

arXiv2025

Inflation in $F(R)$ gravity models revisited after ACT

The $F(R)$ gravity models of inflation are revisited in light of the recent observations of cosmic microwave background radiation by Atacama Cosmology Telescope (ACT) and DESI Collaboration. A detailed study of the evolution equations in the Jordan frame is given and a new description of the slow-roll approximation in the $F(R)$-gravity-based models of inflation is proposed. It is found that all those models of inflation are significantly constrained by demanding a higher (than the Planck Telescope value) cosmological tilt $n_s$ of scalar perturbations and a positive running index $α_s$ favored by ACT. It is not difficult to meet the ACT constraints on the scalar tilt $n_s$ by modifying the existing models of inflation, but simultaneously demanding a positive running $α_s$ would rule out many of them. Using the proposed slow-roll approximation in the Jordan frame, we provide a new modification of the Starobinsky inflation model in the framework of $F(R)$ gravity, which satisfies all ACT constraints. An extension of our ACT-consistent inflation model to the unified $F(R)$-gravity description of Starobinsky-like inflation and production of primordial black holes on a smaller scale is also proposed.

gr-qc↗

arXiv2025

Curvature corrections to Starobinsky inflation can explain the ACT results

We investigate the impact of curvature corrections to Starobinsky inflation in light of the latest observational results from the Atacama Cosmology Telescope (ACT). While the pure Starobinsky model remains a compelling candidate for cosmic inflation, we explore how the higher-order curvature terms $R^3$, $R^{4}$ and $R^{3/2}$ modify the inflationary predictions. Using the scalar-tensor formulation of $f(R)$ gravity, we derive the effective scalar potentials and compute the resulting scalar tilt $n_s$, its running index $α_s$ and the tensor-to-scalar ratio $r$. We show that those curvature corrections can shift the predictions to align better with the ACT data, thus providing a possible resolution to a minor discrepancy between the standard Starobinsky model and ACT observations. Our findings suggest that the modified Starobinsky models with the higher-order curvature terms offer a viable pathway to reconciling inflationary predictions with precision cosmological measurements. At the same time, measuring or constraining primordial tensor modes can help to discriminate between these corrections.

gr-qc↗

arXiv2025

Are single-field models of inflation and PBHs production ruled out by ACT observations?

The data release from the Atacama Cosmology Telescope (ACT) imposes stronger constraints on primordial black holes (PBHs) formation in single-field inflation models versus the Planck data. In particular, the updated Cosmic Microwave Background (CMB) radiation measurements favour a {\it higher} scalar spectral index $n_s$ and its {\it positive} running $α_s$, which put the single-field models under scrutiny. Even in the absence of PBHs production, the new data constrain many single-field models of inflation. To explore this tension, we study PBHs formation in a concrete viable $α$-attractor E-model. We investigate an impact of bending of the inflaton potential plateau toward reconciling the model with the ACT bounds on the CMB observables. We find that attempts to increase $n_s$ through bending lead to negative values of $α_s$. Those values are disfavored by the ACT bounds just above $2σ$ even for PBHs in the asteroid-mass range, while the tension becomes stronger for heavier PBHs.

astro-ph.CO↗

arXiv2025

On Legacy of Starobinsky Inflation

Alexei Alexandrovich Starobinsky was one of the greatest cosmologists of all times, who made fundamental contributions to gravitational theory and cosmology based on geometrical ideas in physics, in the spirit of Einstein. One of his big achievements is the famous Starobinsky model of cosmological inflation in the early universe, proposed in 1979-1980. In this memorial paper, the Starobinsky inflation model is systematically reviewed from the modern perspective. Its deformation to include production of primordial black holes is proposed, and possible quantum corrections in the context of superstring theory and the Swampland Program are discussed. Starobinsky inflation also leads to the universal reheating mechanism for particle production after inflation.

gr-qc↗

arXiv2025

One-loop corrections to the E-type $α$-attractor models of inflation and primordial black hole production

The one-loop corrections (1LC) to the power spectrum of scalar perturbations arising from cubic interactions in the single-field E-type $α$-attractor models of inflation and primordial black hole (PBH) production are numerically calculated. The results demonstrate the 1LC contributes merely a few percent to the tree-level power spectrum. The model parameters are chosen to predict the PBH masses in the asteroid-mass range, while maintaining consistency with the cosmic microwave background (CMB) observations within 1$σ$ confidence levels, and obeying the upper limits on $μ$-distortions. The PBHs formed on scales smaller than the inflation scale can constitute a significant fraction of the present dark matter (DM). The PBH-induced gravitational waves (GW) may be detectable by the future space-based gravitational interferometers. We also consider a reconstruction of the scalar potential from possible GW observations and present a numerical approach tested in the model parameter space.

gr-qc↗

arXiv2024

Starobinsky inflation beyond the leading order

The Starobinsky model of cosmological inflation in four spacetime dimensions is reviewed with the emphasis on impact of quantum gravity corrections. As a specific example of the quantum corrections, the Grisaru-Zanon quartic curvature terms in the gravitational effective action of closed superstrings are chosen. Those quartic curvature terms are compared to the Bel-Robinson tensor squared in a flat Friedman universe, and the upper bound on the effective string coupling constant is found by demanding unitarity (causality) and the absence of ghosts. It is found that the quantum corrections to the observables (tilts) of the cosmic microwave background radiation in the Starobinsky inflation may be of the same order of magnitude as the next-to-next-to-next classical contributions in the Starobinsky model with respect to the inverse powers of the e-folding number at the horizon crossing.

gr-qc↗

arXiv2024

Quantum loop corrections in the modified gravity model of Starobinsky inflation with primordial black hole production

A modified gravity model of Starobinsky inflation and primordial black hole production was proposed in good (within $1σ$) agreement with current measurements of the cosmic microwave background radiation. The model is an extension of the singularity-free Appleby-Battye-Starobinsky model by the $R^4$-term with different values of the parameters whose fine-tuning leads to efficient production of primordial black holes on smaller scales with the asteroid-size masses between $10^{16}$ g and $10^{20}$ g. Those primordial black holes may be part (or the whole) of the current dark matter, while the proposed model can be confirmed or falsified by detection or absence of the induced gravitational waves with the frequencies about $10^{-2}$ Hz. The main purpose of this paper was to estimate the size of quantum (loop) corrections in the model. It was found their relative contribution to the power spectrum of scalar perturbations is about $10^{-3}$ or less, so that the model is not ruled out by the quantum corrections.

gr-qc↗

arXiv2024

Improved model of large-field inflation with primordial black hole production in Starobinsky-like supergravity

A viable model of large-field (chaotic) inflation with efficient production of primordial black holes is proposed in Starobinsky-like (modified) supergravity leading to the "no-scale-type" Kähler potential and the Wess-Zumino-type ("renormalizable") superpotential. The cosmological tilts are in good (within $1σ$) agreement with Planck measurements of the cosmic microwave background radiation. In addition, the power spectrum of scalar perturbations has a large peak at smaller scales, which leads to a production of primordial black holes from gravitational collapse of large perturbations with the masses about $10^{17}$ g. The masses are beyond the Hawking (black hole) evaporation limit of $10^{15}$ g, so that those primordial black holes may be viewed as viable candidates for part or the whole of the current dark matter. The parameters of the superpotential were fine-tuned for those purposes, while the cubic term in the superpotential is essential whereas the quadratic term should vanish. The vacuum after inflation (relevant to reheating) is Minkowskian. The energy density fraction of the gravitational waves induced by the production of primordial black holes and their frequency were also calculated in the second order with respect to perturbations.

astro-ph.CO↗

arXiv2024

Starobinsky inflation and Swampland conjectures

This paper is devoted to memory of late Professor V. G. Bagrov, who was my first teacher in theoretical physics. About 45 years later, theoretical physics has changed and me too. The subject of this paper relates some old ideas in cosmology with some recent ideas, as is reflected in the title. The current status of Starobinsky inflation is reviewed and compared to three main conjectures in the Swampland program. It is argued that the Starobinsky inflation model is not in conflict with those Swampland conjectures in their basic versions.

hep-th↗

arXiv2024

Einstein-Grisaru-Zanon gravity

The leading $(α')^3$-correction to the gravitational low-energy effective action of closed (type II) superstring theory in four-spacetime dimensions defines the Einstein-Grisaru-Zanon gravity action that is applied for a calculation of the leading corrections to the Schwarzschild solution and the Hubble function in the Friedmann-Lemaitre-Robertson-Walker universe, in the first order with respect to the effective string-generated coupling. The solutions found are compared to the corresponding solutions in the Einstein-Bel-Robinson gravity that also modifies the Einstein gravity by the terms quartic in the spacetime curvature. We consider the black hole shadows in the Einstein-Grisaru-Zanon gravity theory and derive the upper bound on the string coupling parameter from the Hawking temperature of a black hole.

hep-th↗

arXiv2024

Dilaton-axion modular inflation in supergravity

Dilaton and axion are ubiquitous in extended supergravities and closed superstrings. We propose new models of modular inflation in four-dimensional $N=1$ supergravity coupled to the chiral dilaton-axion-goldstino supermultiplet, which fit some necessary conditions of superstring cosmology. The model parameters are tuned to obey precision measurements of the cosmic microwave background radiation. We employ the modular-invariant superpotentials and asymptotically modular-invariant Kähler potentials, and achieve axion stabilization with high-scale supersymmetry breaking.

hep-th↗

arXiv2023

Improved model of primordial black hole formation after Starobinsky inflation

A new (improved) model of inflation and primordial black hole (PBH) formation is proposed by combining Starobinsky model of inflation, Appleby-Battye-Starobinsky (ABS) model of dark energy and a quantum correction in the modified $F(R)$ gravity. The energy scale parameter in the ABS model is taken to be close to the inflationary scale, in order to describe double inflation instead of dark energy. The quantum correction is given by the term quartic in the spacetime scalar curvature $R$ with a negative coefficient $(-δ)$ in the $F(R)$ function. It is demonstrated that very good agreement (within $1σ$) with current measurements of the cosmic microwave background (CMB) radiation can be achieved by choosing the proper value of $δ$, thus solving the problem of low values of the tilt of CMB scalar perturbations in the earlier proposed model in arXiv:2205.00603. A large (by the factor of $10^7$ against CMB) enhancement in the power spectrum of scalar perturbations is achieved by fine-tuning the parameters of the model. It is found by numerical analysis that it can lead to formation of asteroid-size PBH with the masses up to $10^{20}$ g, which may form dark matter in the current universe.

gr-qc↗

arXiv2023

Production of primordial black holes in improved E-models of inflation

The E-type $α$-attractor models of single-field inflation were generalized further in order to accommodate production of primordial black holes (PBH) via adding a near-inflection point to the inflaton scalar potential at smaller scales, in good agreement with measurements of the cosmic microwave background (CMB) radiation. A minimal number of new parameters was used but their fine-tuning was maximized in order to increase possible masses of PBH formed during an ultra-slow-roll phase leading to a large enhancement of the power spectrum of scalar (curvature) perturbations by 6 or 7 orders of magnitude against the power spectrum of perturbations observed in CMB. It was found that extreme fine-tuning of the parameters in our models can lead to a formation of Moon-size PBH with the masses of approximately $10^{26}$ g, still in agreement with CMB observations. Quantum corrections are known to lead to the perturbative upper bound on the amplitude of large scalar perturbations responsible for PBH production. The quantum (one-loop) corrections in our models were found to be suppressed by one order of magnitude for PBH with the masses of approximately $10^{19}$ g, which may form the whole dark matter in the Universe.

astro-ph.CO↗

arXiv2023

Primordial black holes from Volkov-Akulov-Starobinsky supergravity

We study the formation of primordial black holes (PBH) in the Starobinsky supergravity coupled to the nilpotent superfield describing Volkov-Akulov goldstino. By using the no-scale Kähler potential and a polynomial superpotential, we find that under certain conditions our model can describe effectively single-field inflation with the ultra-slow-roll phase that appears near a critical (nearly-inflection) point of the scalar potential. This can lead to the formation of PBH as part of (or whole) dark matter, while keeping the inflationary spectral tilt and the tensor-to-scalar ratio in good agreement with the current cosmic microwave background (CMB) bounds. After inflation, supersymmetry is spontaneously broken at the inflationary scale with the vanishing cosmological constant.

hep-th↗