arXiv subjects

Yermek Aldabergenov

Publications and source records attributed to Yermek Aldabergenov.

36 records · Page 2Linked to original sources

arXiv2021

Testing Primordial Black Holes as Dark Matter in Supergravity from Gravitational Waves

We explore the Gravitational Waves (GW) phenomenology of a simple class of supergravity models that can explain and unify inflation and Primordial Black Holes (PBH) as Dark Matter (DM). Our (modified) supergravity models naturally lead to a two-field attractor-type double inflation, whose first stage is driven by Starobinsky scalaron and the second stage is driven by another scalar belonging to a supergravity multiplet. The PBHs formation in our supergravity models is efficient, compatible with all observational constraints, and predicts a stochastic GW background. We compute the PBH-induced GW power spectrum and show that GW signals can be detected within the sensitivity curves of the future space-based GW interferometers such as LISA, DECIGO, TAIJI and TianQin projects, thus showing predictive power of supergravity in GW physics and their compatibility.

hep-th↗

arXiv2021

Nilpotent superfields for broken abelian symmetries

We find new solutions to real cubic constraints on $N=1$ chiral superfields transforming under global abelian symmetries. These solutions describe the low-energy dynamics of a goldstino interacting with an axion (both belonging to the same chiral superfield) with non-linearly realized supersymmetry. We show the relation between our model and the approach of Komargodski and Seiberg for describing goldstino-axion dynamics which uses orthogonal nilpotent superfields.

hep-th↗

arXiv2021

$α$-attractors from supersymmetry breaking

We construct new models of inflation and spontaneous supersymmetry breaking in de Sitter vacuum, with a single chiral superfield, where inflaton is the superpartner of the goldstino. Our approach is based on hyperbolic Kähler geometry, and a gauged (non-axionic) $U(1)_R$ symmetry rotating the chiral scalar field by a phase. The $U(1)_R$ gauge field combines with the angular component of the chiral scalar to form a massive vector, and single-field inflation is driven by the radial part of the scalar. We find that in a certain parameter range they can be approximated by simplest Starobinsky-like (E-model) $α$-attractors, thus predicting $n_s$ and $r$ within $1σ$ CMB constraints. Supersymmetry (and $R$-symmetry) is broken at a high scale with the gravitino mass $m_{3/2}\gtrsim 10^{14}$ GeV, and the fermionic sector also includes a heavy spin-$1/2$ field. In all the considered cases the inflaton is the lightest field of the model.

hep-th↗

arXiv2020

Primordial black holes from modified supergravity

The modified supergravity approach is applied to describe a formation of Primordial Black Holes (PBHs) after Starobinsky inflation. Our approach naturally leads to the two-(scalar)-field attractor-type double inflation, whose first stage is driven by scalaron and whose second stage is driven by another scalar field which belongs to a supergravity multiplet. The scalar potential and the kinetic terms are derived, the vacua are studied, and the inflationary dynamics of those two scalars is investigated. We numerically compute the power spectra and we find the ultra-slow-roll regime leading to an enhancement (peak) in the scalar power spectrum. This leads to an efficient formation of PBHs. We estimate the masses of PBHs and we find their density fraction (as part of Dark Matter). We show that our modified supergravity models are in agreement with inflationary observables, while they predict the PBH masses in a range between $10^{16}$ g and $10^{20}$ g. In this sense, modified supergravity provides a natural top-down approach for explaining and unifying the origin of inflation and the PBHs Dark Matter.

hep-th↗

arXiv2020

Volkov-Akulov-Starobinsky supergravity revisited

We find new realizations of Volkov-Akulov-Starobinsky supergravity, i.e. Starobinsky inflationary models in supergravity coupled to a nilpotent superfield describing Volkov-Akulov goldstino. Our constructions are based on the no-scale Kähler potential $K=-3\log(T+\bar{T})$ for the inflaton field, and can describe de Sitter vacuum after inflation where supersymmetry is broken by the goldstino auxiliary component. In fact, we show that a more general class of models with $K=-α\log(T+\bar{T})$ for $3\leqα\lesssim 6.37$ can accomodate Starobinsky-like inflation with the universal prediction $n_s\simeq 1-\frac{2}{N_e}$ and $r\simeq \frac{4α}{(α-2)^2N_e^2}$, while for $6.37\lesssimα\lesssim 7.23$ viable hilltop inflation is possible (with $n_s$ and $r$ close to the above expressions). We derive the full component action and the masses of sinflaton, gravitino, and inflatino that are generally around the inflationary Hubble scale. Finally, we show that one of our models can be dualized into higher-derivative supergravity with constrained chiral curvature superfield.

hep-th↗

arXiv2020

Minimal Starobinsky supergravity coupled to dilaton-axion superfield

The minimal Starobinsky supergravity with the inflaton (scalaron) and the goldstino in a massive vector supermultiplet is coupled to the dilaton-axion chiral superfield with the no-scale Kähler potential and a superpotential. The Kachru-Kallosh-Linde-Trivedi (KKLT)-type mechanism in the presence of a constant term in the superpotential is applied to stabilize the dilaton/axion during inflation, and it is shown to lead to an instability. The instability is cured by adding the alternative Fayet-Iliopoulos (FI) term that does not lead to the gauged $R$-symmetry. Other stabilization mechanisms, based on the Wess-Zumino (WZ)-type superpotential, are also studied in the presence of the FI term. A possible connection to a D3-brane is briefly discussed too.

hep-th↗

arXiv2020

Aspects of gauged R-symmetry in SU(1,1)/U(1) supergravity

We propose a novel realization of spontaneous supersymmetry breaking in de Sitter vacuum by F- and D-terms in $N=1$ four-dimensional supergravity coupled to a chiral superfield with $SU(1,1)/U(1)$ target space. Our construction features gauged $U(1)_R$ symmetry rotating the chiral scalar field by a phase. Both SUSY and R-symmetry can be spontaneously broken, and for two particular parameter choices we obtain no-scale supergravity with positive tunable cosmological constant.

hep-th↗

arXiv2019

Generalized dilaton-axion models of inflation, de Sitter vacua and spontaneous SUSY breaking in supergravity

We propose the unified models of cosmological inflation, spontaneous SUSY breaking, and the dark energy (de Sitter vacuum) in $N=1$ supergravity with the dilaton-axion chiral superfield $T$ in the presence of an $N=1$ vector multiplet with the alternative Fayet-Iliopoulos term. By using the Kähler potential as $K=-α\log(T+\bar{T})$ and the superpotential as a sum of a constant and a linear term, we find that viable inflation is possible for $3\leqα\leqα_{\rm max}$ where $α_{\rm max}\approx 7.235$. Observations of the amplitude of primordial scalar perturbations fix the SUSY breaking scale in our models as high as $10^{13}$ GeV. In the case of $α>3$ the axion gets the tree-level (non-tachyonic) mass comparable to the inflaton mass.

hep-th↗

arXiv2019

No-scale supergravity with new Fayet-Iliopoulos term

We find a new class of N=1 no-scale supergravity models with F- and D-term supersymmetry breaking, using a new Fayet-Iliopoulos term. The minimal setup contains one U(1) vector multiplet and one neutral chiral multiplet parametrizing SL(2,R)/U(1) manifold, with constant superpotential and linear gauge kinetic function. In our construction the FI term is field-dependent, and one can obtain flat vanishing potential (Minkowski vacuum) with broken SUSY, and global SL(2,R) invariance (self-duality) of the bosonic equations of motion. The spectrum of the model includes a massive spin-1/2 field as well as a vector, a scalar, and a pseudo-scalar -- all classically massless. We discuss several modifications/extensions of the model as well as the introduction of matter fields. We also find a two-field extension of already existing no-scale model.

hep-th↗

arXiv2019

Polonyi-Starobinsky supergravity with inflaton in a massive vector multiplet with DBI and FI terms

We propose the Starobinsky-type inflationary model in the matter-coupled $N=1$ four-dimensional supergravity with the massive vector multiplet that has inflaton (scalaron) and goldstino amongst its field components, whose action includes the Dirac-Born-Infeld-type kinetic term and the generalized (new) Fayet-Iliopoulos-type term, without gauging the R-symmetry. The $N=1$ chiral matter ("hidden sector") is described by the modified Polonyi model needed for spontaneous supersymmetry breaking after inflation. We compute the bosonic action and the scalar potential of the model, and show that it can accommodate the positive (observed) cosmological constant (as the dark energy) and the spontaneous supersymmetry breaking at high scale after the Starobinsky inflation.

hep-th↗

arXiv2019

Modified Born-Infeld-dilaton-axion coupling in supersymmetry

We propose the supersymmetric extension of the modified Born-Infeld-axion-dilaton non-linear electrodynamics that has confined static abelian solutions used for describing the electromagnetic confinement in the presence of axion and dilaton fields, and charged matter. The supersymmetric extension also has the non-trivial scalar potential that implies the upper bounds on the matter fields.

hep-th↗

arXiv2018

Massive vector multiplet with Dirac-Born-Infeld and new Fayet-Iliopoulos terms in supergravity

We propose a four-dimensional N = 1 supergravity-based Starobinsky-type inflationary model in terms of a single massive vector multiplet, whose action includes the Dirac-Born-Infeld-type kinetic terms and a generalized (new) Fayet-Iliopolulos-type term without gauging the R-symmetry. The bosonic action and the scalar potential are computed. Inflaton is the superpartner of goldstino in our model, and supersymmetry is spontaneously broken after inflation by the D-type mechanism, whose scale is related to the value of the cosmological constant.

hep-th↗

arXiv2018

Beyond Starobinsky inflation

A supergravity extension of the $(R+R^2)$ gravity with the additional (Born-Infeld) structure of a massive vector multiplet gives rise to the specific $F(R)$ gravity, whose structure is investigated in detail. The massive vector multiplet has inflaton (scalaron), goldstino and a massive vector field as its field components. The model describes Starobinsky inflation and allows us to extrapolate the $F(R)$ function beyond the inflationary scale (up to Planck scale). We observe some differences versus the $(R+R^2)$ gravity, and several breaking patterns of the well known correspondence between the $F(R)$ gravity and the scalar-tensor gravity.

hep-th↗

arXiv2018

General couplings of a vector multiplet in N=1 supergravity with new FI terms

We propose new interactions of a (massive) vector multiplet with chiral multiplets and (D-type) spontaneously broken supersymmetry in four-dimensional N=1 supergravity, due to the generalized Fayet-Iliopoulos (FI) terms. Our actions are invariant under linearly realized off-shell supersymmetry and Kaehler-Weyl transformations. We compute the scalar potentials and pinpoint some physical restrictions arising in this approach.

hep-th↗

arXiv2018

Removing instability of Polonyi-Starobinsky supergravity by adding FI term

Polonyi-Starobinsky (PS) supergravity is the N=1 supergravity model of Starobinsky inflation with spontaneous supersymmetry breaking (after inflation) due to Polonyi superfield, and inflaton belonging to a massive vector supermultiplet. The PS model is used for an explicit realization of the (super-heavy) gravitino dark matter scenario in cosmology. We find a potential instability in this model, and offer a mechanism for its removal by adding a Fayet-Iliopoulos (FI) term.

hep-th↗

arXiv2017

SUSY breaking after inflation in supergravity with inflaton in a massive vector multiplet

We propose a limited class of models, describing interacting chiral multiplets with a non-minimal coupling to a vector multiplet, in curved superspace of $N=1$ supergravity. Those models are suitable for the inflationary model building in supergravity with inflaton assigned to a massive vector multiplet and spontaneous SUSY breaking in Minkowski vacuum after inflation, for any values of the inflationary parameters $n_s$ and $r$, and any scale of SUSY breaking.

hep-th↗

arXiv2017

Higgs mechanism and cosmological constant in $N=1$ supergravity with inflaton in a vector multiplet

The $N=1$ supergravity models of cosmological inflation with inflaton belonging to a massive vector multiplet and spontaneous SUSY breaking after inflation are reformulated as the supersymmetric $U(1)$ gauge theories of a massless vector superfield interacting with the Higgs and Polonyi chiral superfields, all coupled to supergravity. The $U(1)$ gauge sector is identified with the $U(1)$ gauge fields of the super-GUT coupled to supergravity, whose gauge group has a $U(1)$ factor. A positive cosmological constant (dark energy) is included. The scalar potential is calculated, and its de Sitter vacuum solution is found to be stable.

hep-th↗

arXiv2014

Some effects of nonlinear vacuum electrodynamics in strong magnetic and gravitational fields of the pulsar

We consider the propagation of X-ray and gamma ray emissions in strong magnetic and gravitational fields of the pulsar in nonlinear vacuum electrodynamics. We show that the radiation will spread from the pulsar to the detecting device in the form of two normal modes polarized in mutually orthogonal planes, and having different velocities. We have calculated the delay between the two modes, as they propagate from the pulsar to the detecting device.

gr-qc↗