arXiv subjects

Davood Momeni

Publications and source records attributed to Davood Momeni.

At least 19 recordsLinked to original sources

arXiv2025

Extended Entropic Dark Energy with Four Free Parameters: Theory, Dynamics, and Constraints

We investigate a four-parameter entropic dark energy model in a spatially curved FLRW universe, based on a generalized entropy-area relation at the apparent horizon. While the proposed entropy function captures a broad class of gravitational entropy corrections, including Bekenstein-Hawking, Tsallis, and power-law forms, it does not encompass information-theoretic entropies such as Sharma-Mittal or Renyi. Within this framework, we derive exact analytical expressions for key cosmological observables, including the Hubble parameter $H(z)$, the dark energy density parameter $\Omega_D(z)$, and the equation of state $w_D(z)$. A comprehensive parameter-space analysis reveals viable regions, particularly for $\beta > 1$ and small positive curvature, that accommodate elevated $H_0$ values consistent with recent SH0ES measurements. Our results offer a simple and analytically tractable alternative to conventional dynamical dark energy models, with potential relevance to the ongoing Hubble tension.

gr-qc↗

arXiv2025

Recalibrating Inflation: Insights from Starobinsky Gravity

Recent analyses of low-redshift supernova and Cepheid data reveal localized shifts in the distance modulus, often interpreted as calibration anomalies or hints of new physics. We propose that these features may emerge naturally from environment-dependent modifications to gravity. In particular, we examine the Starobinsky $f(R) = R + \lambda R^2$ model, which introduces a scalar degree of freedom that couples to ambient matter density and alters photon propagation in underdense regions. We derive the corresponding corrections to luminosity distance and show that they can reproduce the observed magnitude shifts without invoking discontinuities or empirical step functions. Statistical comparisons using AIC and BIC favor the Starobinsky framework over phenomenological models, supporting its role as a minimal, geometric explanation for emergent calibration transitions.

astro-ph.CO↗

arXiv2025

Wald Entropy in Extended Modified Myrzakulov Gravity Theories: $f(R, T, Q, R_{\mu\nu}T^{\mu\nu}, R_{\mu\nu}Q^{\mu\nu}, \dots)$

We investigate black hole entropy in a broad class of modified Myrzakulov gravity theories defined by generalized Lagrangians of the form $ \mathcal{L} = \alpha R + F(T, Q, R_{\mu\nu}T^{\mu\nu}, R_{\mu\nu}Q^{\mu\nu}, \dots) $, where $ R $, $ T $, and $ Q $ represent curvature, torsion, and non-metricity scalars. Using the vielbein formalism, we derive the Wald entropy for various subclasses of these models, extending the classical entropy formula to accommodate non-Riemannian geometry. Our focus is on how the additional geometric degrees of freedom modify the entropy expression. The analysis shows that such corrections arise systematically from the extended structure of the action and preserve diffeomorphism invariance. These results refine the theoretical framework for gravitational thermodynamics in extended geometry settings.

gr-qc↗

arXiv2025

From geometry to cosmology: a pedagogical review of inflation in curvature, torsion, and extended gravity theories

We present a simplified review of inflationary cosmology across various modified gravity theories. These include models based on curvature, torsion, and non-metricity. We explore how scalar fields interact with different geometric quantities and how these interactions affect inflationary dynamics. Key cosmological features such as background evolution, reheating, and observable parameters are discussed. We also examine exotic scenarios inspired by string theory, extra dimensions, and non-local models. This work aims to connect theoretical models with observational data and future missions, offering guidance for exploring inflation beyond general relativity.

gr-qc↗

arXiv2025

Entanglement Suppression in Quantum Field Theories: Holography, Chaos, and Mixed-State Dynamics

Recent work has revealed that entanglement entropy growth in conformal field theories (CFTs) can be suppressed when a local operator quench interacts with a mixed-state excitation, providing a dual interpretation in terms of black hole scattering in AdS. This phenomenon, termed \emph{entanglement suppression}, opens several promising directions for exploration. In this proposal, I outline five distinct yet interconnected research trajectories: generalization to higher dimensions, the role of quantum chaos via out-of-time-order correlators (OTOCs), the absence of suppression in integrable models, the extension to entanglement negativity as a probe of mixedness, and a geometric interpretation based on scattering cross sections in AdS. Each direction offers new insights into the interplay between holography, non-equilibrium dynamics, and quantum information.

quant-ph↗

arXiv2025

Cosmological Reconstructions in Einstein--Cartan--Myrzakulov Gravity with Torsion and Non-Metricity in the Weitzenb\"ock Geometrical Sector

The universe is a vast and complex system, and our understanding of its fundamental workings is constantly evolving. In this work, we present a novel modification to the standard theory of gravity by incorporating curvature, torsion, non-metricity, and the geometric structure of Weitzenb\"{o}ck spacetime. This modified framework, referred to as the Einstein--Cartan--Myrzakulov (ECM) model, enriched by Weitzenb\"{o}ck geometry, offers new insights into cosmological phenomena, including the accelerated expansion of the universe, the nature of dark energy and dark matter, and the formation of cosmic structures. Our model not only reproduces observed cosmic histories but also provides testable predictions that can be compared with current and future observational data. By addressing some of the most profound questions in modern cosmology, this work paves the way for a deeper understanding of the universe's evolution and the fundamental forces that govern it. The ECM model, extended through Weitzenb\"{o}ck spacetime, invites further exploration, offering the potential to revolutionize our conception of gravity and the cosmos.

gr-qc↗

arXiv2025

Dark Matter Constraints in Myrzakulov $F(R,T)$ Gravity: A Vielbein Approach in Weitzenb\"{o}ck Spacetime with Observational Data

We explore dark matter phenomenology in Myrzakulov $F(R,T)$ gravity, formulated via the vielbein approach in Weitzenb\"{o}ck spacetime. In this torsion-based extension of gravity, dark matter emerges as a geometric effect rather than a particle species, with curvature and torsion contributing dynamically to the field equations. Using recent data -- including SPARC galaxy rotation curves, Planck CMB observations, and weak lensing from DES and KiDS -- we constrain the model through MCMC analysis. Our results show that, under specific parameter choices, the theory replicates key cosmological features without introducing additional dark sector matter. This framework offers a testable alternative to $\Lambda$CDM, providing new insight into structure formation, gravitational lensing, and cosmic acceleration -- all rooted in the geometry of spacetime.

gr-qc↗

arXiv2025

Inverse Hamiltonian Reconstruction from Gravitational Energy Density in Curved Spacetime

We present a general framework for reconstructing effective Hamiltonians from known gravitational energy density profiles in curved spacetime. Starting from local thermal equilibrium and Liouville dynamics, we establish an inverse procedure that relates the macroscopic energy density $ \rho(x) $ to a distribution function $ f(x,p) \sim e^{-\beta H(x,p)} $, and recovers the underlying Hamiltonian $ H(x,p) $ via functional inversion. This approach synthesizes tools from relativistic kinetic theory, statistical mechanics, and covariant gravitational thermodynamics, offering a systematic way to extract microscopic dynamics from coarse-grained energy observables. Applications include FLRW cosmology, Loop Quantum Gravity corrections, AdS/CFT holography, and the SYK model. Our results provide a novel route for probing emergent spacetime dynamics through observable densities, bridging geometry, entropy, and Hamiltonian flow in curved backgrounds.

gr-qc↗

arXiv2025

Inflation in Myrzakulov $F(R,T)$ Gravity: A Comparative Study in Metric, Symmetric Teleparallel, and Weitzenb\"{o}ck Formalisms

We present a unified treatment of cosmic inflation within the framework of Myrzakulov Gravity, exploring its realization in three different formalisms: metric (curvature-based), teleparallel (torsion-based), and symmetric teleparallel (non-metricity-based). For each case, we derive the corresponding field equations in a flat FLRW background, study inflationary solutions driven by a scalar field, and compute observable quantities such as the scalar spectral index $ n_s $ and the tensor-to-scalar ratio $ r $. In addition to these geometric sectors, we extend our analysis to the more general and dynamically richer Myrzakulov $ F(R,T) $ gravity, which incorporates both curvature $ R $ and torsion $ T $ in a unified action. We derive the inflationary dynamics in this hybrid model and investigate how it interpolates between pure $ f(R) $ and $ f(T) $ behaviors. The resulting framework allows for enhanced flexibility in matching Planck and BICEP/Keck observational constraints. We present analytic estimates and schematic predictions in the $ n_s $--$ r $ plane, demonstrating that appropriately chosen parameters in $ F(R,T) $ models can produce viable and distinguishable inflationary signatures. This comparative and extended study highlights the potential of Myrzakulov Gravity and its generalizations to provide a consistent and geometrically motivated description of the early universe, with predictive power across different formulations of spacetime geometry.

gr-qc↗

arXiv2025

Comment on "On the bound states of the Schwarzschild black hole" by S. H. V\"olkel: A Reassessment of the Bound-State Analogy

This comment critically examines the recent proposal by S.~H.~V\"olkel [Phys. Rev. Lett., arXiv:2505.17186], which asserts that the quasinormal mode (QNM) spectrum of Schwarzschild black holes can be reconstructed from bound states of an inverted Regge--Wheeler potential. We demonstrate that this claim rests on a mathematically invalid spectral mapping and a misapplication of boundary conditions that define QNMs. Through a detailed figure-by-figure analysis, we expose deep inconsistencies in the numerical results and their physical interpretations. The inversion method, inspired by Mashhoon, is shown to fail in capturing the non-Hermitian, complex nature of black hole resonances. We contrast this with the rigorously established asymptotic structure of QNMs derived by Hod and others, concluding that the bound-state framework offers no reliable insight into black hole spectroscopy.

gr-qc↗

arXiv2025

Einstein-Gauss-Bonnet-Myrzakulov Gravity from $R + F(T, G)$: Numerical Insights and Torsion-Gauss-Bonnet Dynamics in Weitzenb\"ock Spacetime

The study of modified gravity models has garnered significant attention because of their potential to provide alternative explanations for cosmological phenomena, such as the accelerated expansion of the universe and the nature of dark energy. One such model, the Einstein-Gauss-Bonnet-Myrzakulov $R + F(T, G)$ gravity (EGBMG), which incorporates the curvature $R$, torsion $T$, and the Gauss-Bonnet term $G$, offers a promising framework to explore the dynamics of the universe and its evolution. This paper delves into the theoretical and observational implications of the EGBMG model, focusing on its ability to address long-standing challenges in cosmology, including the evolution of dark energy and the transition from early-time inflationary behavior to late-time acceleration. We review recent advancements in the model, including its compatibility with observational data and its ability to provide new insights into cosmic acceleration. Through a combination of theoretical models, dynamical systems analysis, and cosmological diagnostics, we demonstrate the robustness of the EGBMG framework in explaining the large-scale structure of the universe and its accelerated expansion. This paper serves as a step toward further exploring the potential of this model to understand the fundamental forces driving Weitzenb$\"{o}$ck spacetime.

gr-qc↗

arXiv2025

Metric-Affine Myrzakulov Gravity Theories: Models, Applications and Theoretical Developments

This review presents a comprehensive overview of Myrzakulov gravity, highlighting key developments and significant results shaping the theory. It examines the foundational principles, field equations, and the role of non-metricity and torsion in gravitational interactions. The theory's implications extend to cosmology, astrophysics, and strong gravitational fields, offering alternatives to dark matter and dark energy. A focus is placed on the modified Einstein-Hilbert action, its impact on cosmic expansion, and astrophysical applications such as black holes and gravitational waves. Observational constraints from cosmology and gravitational wave tests are discussed to refine the model. By situating Myrzakulov gravity within the broader context of modified gravity, this review explores its potential to reshape fundamental physics.

gr-qc↗

arXiv2024

Myrzakulov Gravity in Vielbein Formalism: A Study in Weitzenb\"ock Spacetime

The quest to understand gravity's role in shaping the universe has led to the exploration of modified gravity theories. One such theory is Myrzakulov gravity, which incorporates both curvature and torsion. In this work, we investigate the effects of torsion within the framework of $f(R,T)$-gravity, a modification of General Relativity that includes both curvature and torsion. We present this theory in the Vielbein formalism, which offers a more flexible, geometric perspective on gravity. This formalism is particularly useful in Weitzenb"ock spacetime, where torsion significantly influences gravitational interactions. Our study aims to extend Myrzakulov's theory and explore its cosmological and astrophysical implications. We examine the effects of torsion on phenomena like black holes, gravitational waves, and neutron stars. These modifications could lead to observable deviations in black hole thermodynamics, gravitational wave propagation, and dense matter structure. This work provides new insights into the nature of spacetime and gravity, offering a fresh perspective on the fundamental forces governing the cosmos. It paves the way for future studies, both observational and theoretical, that could reveal new physics beyond General Relativity.

gr-qc↗

arXiv2024

Warm non-minimally coupled Peccei-Quinn Inflation and de Sitter Swampland Conjecture

In this study, we explore the dynamics of warm inflation within a non-minimally coupled Peccei-Quinn (PQ) framework and evaluate its compatibility with the de Sitter Swampland Conjecture. Our model incorporates a PQ scalar field that is non-minimally coupled to gravity, facilitating inflation through a dissipative process that sustains a thermal bath, thereby distinguishing it from conventional cold inflation. We analyze the dissipation coefficient defined as $\Gamma(T, \sigma) = C_n T^n \sigma^p M^{1-n-p}$, where $C_n$ is a dimensionless constant, $M$ is a mass scale, and $n$ and $p$ are numerical powers. Our investigation focuses on three specific cases: (a) A temperature-dependent dissipation coefficient with an inverse relation, $\Gamma = C_{-1}\,\sigma^2/T$, where $n=-1$ and $p=2$; (b) A dissipation coefficient linear in field $\phi$, $\Gamma = C_{0} \sigma$, where $n=0$ and $p=1$; and (c) A dissipation coefficient linear in temperature $T$, $\Gamma = C_{1} T$, where $n=1$ and $p=0$. By examining the slow-roll dynamics in these inflationary scenarios, we derive essential cosmological parameters, including the scalar spectral index and the tensor-to-scalar ratio. We compare our results with the latest observational data from Planck 2018. Our findings suggest that the model is consistent with observational constraints while simultaneously satisfying the de Sitter Swampland conditions.

gr-qc↗

arXiv2024

Gravity Rainbow Effects on Higher Curvature Modification of R2 inflation

In this work, we study several extensions of the higher curvature modification of $R^{2}$ inflation in the context of gravity's rainbow. We modify the $(R+R^{2})$ model by adding an $f_{1}R^3$-term, an $f_{2}R^4$-term, and an $f_{3}R^{3/2}$-term to the original model. We calculate the inflationary observables and confront them using the latest observational bounds from Planck 2018 data. We assume the rainbow function of the form $\tilde{f}=1+\left(\frac{H}{M}\right)^{λ}$ with $λ$ being a rainbow parameter and $M$ a mass-dimensional parameter. We demonstrate that the power spectrum of curvature perturbation relies on the dimensionless coefficient $f_{i},\,i=1,2,3$, a rainbow parameter $λ$ and a ratio $H/M$. Likewise, the scalar spectral index $n_s$ is affected by both $f_{i}$ and the rainbow parameter. Moreover, the tensor-to-scalar ratio $r$ is solely determined by the rainbow parameter. Interestingly, by ensuring that $n_s$ aligns with the Planck collaboration's findings at the $1σ$ confidence level, the tensor-to-scalar ratio could reach up to $r\sim 0.01$, which is possibly measurable for detection in forthcoming Stage IV CMB ground experiments and is certainly feasible for future dedicated space missions.

gr-qc↗

arXiv2024

Exploring Self-Gravitating Cylindrical Structures in Modified Gravity: Insights from Scalar-Vector-Tensor Theory

We investigate static cylindrical solutions within an extended theory of modified gravity. By incorporating various coupling functions through a straightforward boost symmetry approach, we establish the equations of motion in a self-consistent manner and subsequently determine the linear scalar field profile. Utilizing analytical methods, we solve the system of equations for the metric functions and the $U(1)$ gauge field, revealing their dependence on Bessel's functions. To comprehend gravito-objects exhibiting cylindrical symmetry, we develop a perturbative framework aimed at identifying all nontrivial solutions for the scalar profiles. Introducing first-order truncated perturbation equations for the gauge field, synchronized with metric gauges and electromagnetic field considerations, we demonstrate their integrability and obtain solutions through quadrature. Our findings suggest the feasibility of obtaining self-gravitating cylindrical structures within the scalar-vector-tensor theory.

gr-qc↗

arXiv2024

Unveiling Novel Insights in Quantum Dynamics through Extended Sachdev-Ye-Kitaev Model

Inspired by recent developments in the study of the model of double scaled SYK (DSSYK), as elucidated in a recent paper, we embark on a re-evaluation of the Sachdev-Ye-Kitaev (SYK) model. Our motivation stems from the insights gained from the DSSYK model, particularly its ability to capture essential features of quantum dynamics and gravitational effects. In this work, we delve into the SYK model, uncovering precise solutions for the two-point function and self-energy that have not been previously reported. Building upon the advancements made in particle physics phenomenology, we extend the SYK model to encompass tensor field theory. Through the incorporation of a cutoff term to ensure convergence, we substantially advance our understanding of quantum many-body physics. Our investigation extends to experimental parameter estimation and the exploration of cutoff dependency in random couplings, providing invaluable insights into system dynamics. The introduction of a novel tensor field theory replaces conventional fermionic degrees of freedom with tensorial counterparts, leading to the discovery of intriguing phase transition phenomena characterized by a first-order transition. Furthermore, we elucidate a direct linear relationship between the coupling parameter and the cutoff scale. These findings not only shed light on emergent behavior across both high-energy physics and condensed matter systems but also pave the way for further theoretical and experimental exploration, inspired by the recent advancements in the SYK model.

hep-th↗

arXiv2024

Observation of Floquet states in graphene

Recent advances in the field of condensed-matter physics have unlocked the potential to realize and control emergent material phases that do not exist in thermal equilibrium. One of the most promising concepts in this regard is Floquet engineering, the coherent dressing of matter via time-periodic perturbations. However, the broad applicability of Floquet engineering to quantum materials is still unclear. For the paradigmatic case of monolayer graphene, the theoretically predicted Floquet-induced effects, despite a seminal report of the light-induced anomalous Hall effect, have been put into question. Here, we overcome this problem by using electronic structure measurements to provide direct experimental evidence of Floquet engineering in graphene. We report light-matter-dressed Dirac bands by measuring the contribution of Floquet sidebands, Volkov sidebands, and their quantum path interference to graphene's photoemission spectral function. Our results finally demonstrate that Floquet engineering in graphene is possible, paving the way for the experimental realization of the many theoretical proposals on Floquet-engineered band structures and topological phases.

cond-mat.mes-hall↗