arXiv subjects

Daulet Berkimbayev

Publications and source records attributed to Daulet Berkimbayev.

12 recordsLinked to original sources

arXiv2026

DESI and Dynamical Dark Energy from Extended Pre-geometric Gravity

We consider the simplest quadratic extension of MacDowell--Mansouri pre-geometric gravity that preserves the topological pre-volume-form symmetry. Upon symmetry breaking, the theory reduces to $(\mathrm{Lovelock})^2$ gravity and admits a Galileon-like Horndeski scalar-tensor representation. The gravitational Higgs mechanism relates the Gauss--Bonnet coupling to the bare cosmological constant, while the quadratic correction elevates the gravitational $θ$-angle to a dynamical gravi-axion whose ultra-light mass scale can drive late-time acceleration. We confront the Jordan-frame background with DESI DR2 baryon-acoustic-oscillation measurements and an auxiliary six-point compressed growth diagnostic. A transient dark-energy response localized near $H\simeq m_b$ ($m_b$ the effective gravi-axion mass) reproduces the fitted expansion and its BAO-distance predictions and becomes negligible at high redshift. For the full linear calculation, we combine a smooth positive-density representative of this response class with explicitly imposed GR-like tensor and local sectors, together with the parameterized post-Friedmann prescription. The resulting gravi-axion benchmark exhibits a transient effective phantom crossing and admits a regular full linear CAMB evolution. Its separate likelihood contributions are promising relative to those obtained from the flat-$Λ$CDM baseline for the same data set. These results establish the dynamical gravi-axion framework, dual to MacDowell--Mansouri pre-geometric gravity, as a viable effective quantum-gravity inspired description of late-time cosmology, motivating further investigation into its fundamental origin and perturbative consistency.

gr-qc↗

arXiv2026

Relational Wigner-Smith Duration in Wheeler-DeWitt Scattering

A closed Friedmann-Lemaitre-Robertson-Walker Wheeler-DeWitt model is formulated as an exact reflection problem. The derivative of its reflection phase defines a relational crossing duration whose first two clock moments follow from a covariant scalar-clock observable. An analytic expression is obtained for this duration, its classical recollapse limit, and the leading quantum correction. A finite spectral packet also gives an operational, equal-prior minimum error probability for distinguishing the two orientations of recollapse with a geometric reading. The construction is extended to a bounded finite quantum detector. Its multichannel reflection matrix yields probe transitions, spectral-probe correlations, and a matrix duration. A direct weak-coupling calculation verifies the predicted transition and duration scalings. Scalar-clock conditioning and oriented geometric sections are shown to be local representations of the same positive-frequency Dirac sector. These results define duration and transition observables entirely through correlations and scattering records of a stationary constrained state, without introducing a background clock.

gr-qc↗

arXiv2026

(Lovelock)$^2$ inflation: explaining the ACT data and equivalence to Higgs-Gauss-Bonnet inflation

We revisit the Starobinsky model of inflation in light of recent data from the Atacama Cosmology Telescope (ACT), which indicates a potential preference for a slightly larger scalar spectral index $n_s$ than predicted by the standard $R^2$ scenario. We demonstrate that a natural one-parameter generalization to a quadratic model $\sim L+L^2$ in the Lovelock invariant $L=R+\fracα{4}{\cal G}$ ($\cal G$ is the Gauss--Bonnet term), can effectively resolve this minor tension. Scalar-tensor formulation of this theory yields an Einstein-frame Starobinsky-type scalar potential augmented by Gauss--Bonnet and derivative couplings, which modify the inflationary slow-roll dynamics. We show that a non-zero coupling $α$ for the Gauss-Bonnet term can shift $(n_s, r)$ along a trajectory that brings the predictions into better agreement with the ACT likelihood. We also find that $L+L^2$ gravity, in its scalar-tensor formulation, is equivalent to Higgs inflation coupled to the Gauss--Bonnet term, and belongs to the Horndeski/galileon class of modified gravities. This work establishes the quadratic $f(L)$ gravity as a compelling and physically motivated extension that preserves the successes of Starobinsky inflation while improving its fit to modern precision cosmological data.

gr-qc↗

arXiv2026

Domain Wall formation from $Z_2$ spontaneous symmetry breaking/restoration in Scalar-Einstein-Gauss-Bonnet theory

This study offers a detailed analysis of domain wall formation and its cosmological consequences in Einstein-Gauss-Bonnet gravity coupled to a scalar field. A central aspect of the model is the scalar field Lagrangian's ability to spontaneously break and restore its $Z_2$ discrete symmetry. This spontaneous symmetry breaking is a fundamental prerequisite for topological defect formation. In this context, domain walls arise as kink-like, solitonic solutions that interpolate between the distinct vacuum states of the theory. We perform a detailed numerical analysis of the dynamics of a neutral scalar field non-minimally coupled to the Gauss-Bonnet invariant, exploring its behavior across different cosmological backgrounds. Our results show that coupling to the Gauss-Bonnet term enables the formation of static domain walls with a fixed proper distance within a de Sitter (inflationary) background. Furthermore, we extend our analysis to a radiation-dominated epoch, where we identify that the cosmic expansion causes the "melting" of these domain walls. To assess the potential observational signatures of this scenario, we calculate the predicted spectrum of stochastic gravitational waves generated by the network dynamics using {\it CosmoLattice} package. We also examine the possible generation of Primordial Black Holes (PBHs) associated with collapsing domain walls. Regrettably, our calculations indicate that the direct observational detection of such domain walls from this model lies beyond the reach of foreseeable experiments. Our results constitute a No-Go argument against the generation of PBHs as well as of large amplitude GW signals from domain walls in a Scalar-EGB spontaneous symmetry breaking mechanism.

hep-th↗

arXiv2026

Regular hairy black holes by gravitational decoupling: Bardeen and Minkowski-core seeds

We construct two families of regular hairy black holes within gravitational decoupling using a fixed exponential deformation profile for an effective tensor-vacuum sector. The first family is generated from a Bardeen-type seed and produces a de Sitter-like core. The second family is generated from a hollow seed with an asymptotically Minkowski core so that the central density vanishes and no de Sitter core is produced. For each branch we determine the critical deformation strengths separating horizonless, extremal, and two-horizon geometries in the static case, and we obtain the corresponding Kerr-like rotating extension by promoting the mass parameter to the deformed mass function. Representative parameter choices are used to illustrate the horizon structure and to verify the weak energy condition in the exterior region.

gr-qc↗

arXiv2026

Classical Corrections to Black Hole Entropy II

We reconsider the classical one bit absorption model of black hole growth as a discrete recursion rather than a continuum equation. In this paper, one bit means one elementary absorption unit measured in natural logarithmic units. For a Schwarzschild Tangherlini black hole, the discrete treatment gives the expected area scaling and also produces a logarithmic correction. The coefficient of this correction is fixed by the dimensional dependence of the mass step. We then extend the construction to the Reissner Nordström case at fixed charge. In this sector, the logarithmic coefficient gains an explicit charge dependence. The fixed charge calculation can be interpreted as the large mass neutral growth stage after a charged seed has already formed. In that interpretation, realistic charged absorption affects the initial cutoff, while the large mass recursion controls the dominant entropy for weakly charged final states. We also study ordered histories built from positively charged, negatively charged, and neutral labels. These histories define a formal ensemble rather than a direct count of black hole microstates. In a unitary description, two different histories may lead to the same reduced macroscopic state, described by mass, charge, and entropy, while remaining different in hidden or environmental degrees of freedom. Adding a mass or energy label reduces the endpoint degeneracy, but it does not remove it in the ensembles considered here. The corrected interpretation separates dynamical entropy, thermodynamic state entropy, history entropy, and hidden conditional entropy. It also clarifies that the multinomial formula is a restricted history counting result, not a proof that different histories correspond to unique or identical microscopic black hole states.

gr-qc↗

arXiv2025

Discrete Action, Graph Evolution, and the Hierarchy of Symmetries: A Rigorous Construction of Temporal Layers $C1 \to C2 \to C3 \to C4$

Postulating a minimal discrete quantum of action $S=\hbar$ and a simple rule for the growth of an oriented graph, we construct a strict hierarchy of temporal layers $C N$ with discrete periods $τ_N=N\hbar/E$. Each layer is specified by its configuration space, symplectic structure, update rule, and emergent symmetry. At $C1$ the state is represented by a single oriented edge with $U(1)$ phase $e^{i E t/\hbar}$. The transition $C1 \to C2$ splits the edge into two independent flows, which yields canonical pairs $(x_a,p_a)$, local $U(1)$ invariance, and an effective $(2{+}1)$ metric with signature $(+--)$. The closure $C2 \to C3$ produces $SU(3)$ connections and an Einstein-Yang-Mills type action. We show that these structures follow from discrete-action principles, and that stochastic graph growth naturally provides mechanisms for decoherence and spontaneous symmetry breaking.

physics.gen-ph↗

arXiv2025

Energy transfer between the sources in gravitational decoupling

A straightforward and fully analytic approach is introduced to examine how polytropic fluids influence arbitrary gravitational sources in static, spherically symmetric spacetimes. As a concrete application, we explore the internal mechanism of energy transfer between gravitational sources embedded within a self-gravitating system.

gr-qc↗

arXiv2025

Effects of matter with anisotropic pressure on the Fan-Wang regular black hole shadows

We here investigate the consequences of an exotic fluid, exhibiting negative radial and tangential pressures, \emph{de facto} violating the Zel'dovich limit, on a regular solution that easily generalizes the Schwarzschild black hole. More precisely, we focus on the regular Fan-Wang spacetime, computing how the black hole shadow images, surrounded by the quoted fluid, is modified through the presence of \emph{negative} equations of state for the two pressure components. Even though quite different from quintessence, we consider constant radial and tangential equations of state with the aim of emulating, but not reproducing, dark energy effects. Moreover, we explore the main properties of infalling spherical accretion flows and, accordingly, the influence of the equations of state on the horizons, photosphere, and impact parameter of the Fan-Wang black hole. Afterwards, we examine the luminosities of the shadow and the photon ring in two distinct spherically accretion flows, as well as the observed specific intensity of the shadow itself. Last but not least, we physically interpret the impact of negative pressures on our findings and discuss possible extensions to the isotropic case.

gr-qc↗

arXiv2025

Gauss-Bonnet-induced symmetry breaking/restoration during inflation

We propose a mechanism of symmetry breaking or restoration that can occur in the middle of inflation due to the coupling of the Gauss-Bonnet term to a charged scalar. The Gauss-Bonnet coupling results in an inflaton-dependent effective squared mass of the charged scalar, which can change its sign (around the symmetric point) during inflation. This can lead to spontaneous breaking of the symmetry, or to its restoration, if it is initially broken. We show the conditions under which the backreaction of the Gauss-Bonnet coupling on the inflationary background is negligible, such that the predictions of a given inflationary model are unaffected by the symmetry breaking/restoration process.

hep-th↗

arXiv2023

Charge gap in SU(3) Yang-Mills-plus-nonlinear-spinor-field theory

Particlelike solutions in SU(3) gauge Yang-Mills theory with color magnetic and electric fields sourced by a nonlinear spinor field are obtained. The asymptotic behavior of these fields is studied. It is shown that the electric field exhibits the Coulomb asymptotic behavior, and one of the color components of the magnetic field behaves asymptotically as the field of a magnetic dipole. This allows one to determine the corresponding charge and magnetic moment. It is shown that profiles of the color charge and magnetic moment have global minima, which may be called charge and magnetic moment gaps. The relationship between the total energy of the system and the color charge is obtained. The physical reason for the appearance of the mass, charge, and magnetic moment gaps in the theory under consideration is discussed.

hep-th↗

arXiv2022

More on gravitational waves from double monodromy inflation

We further analyze phenomenological implications of double axion monodromy inflation proposed in Ref. Phys. Rev. D 104, L081302 (2021), in gravitational wave physics. We show that in addition to chiral gravitational waves (GW) originating from gauge field instability, the model also predicts significant amount of non-chiral, scalar-induced gravitational waves, both peaking at around the same frequencies. We find that although chiral GW density has much larger peak, non-chiral GWs can dominate away from the peak as they decay at a slower rate. This provides an interesting GW signature to be probed by future space-based interferometers such as LISA and DECIGO.

gr-qc↗