Urgench State University
We investigate the inflationary phenomenology of a marginally deformed Starobinsky model, motivated by quantum corrections to the R2R^{2} term, in light of the latest cosmological observations. In this framework, the inflationary potential acquires a small deformation parameter, γ\gamma, which shifts predictions away from the exact Starobinsky limit. Using the slow-roll formalism, we derive analytic expressions for the spectral index nsn_{s} and tensor-to-scalar ratio rr and confront them with constraints from Planck, ACT, and DESI data. Our analysis shows that nonzero values of γ\gamma raise both nsn_{s} and rr, thereby alleviating the 2σ\gtrsim 2\sigma tension between the Starobinsky R2R^{2} scenario and the ACT+DESI (P-ACT-LB) measurements, which favor ns0.9743±0.0034n_{s} \simeq 0.9743 \pm 0.0034. For N60N \sim 60 ee-foldings, the model consistently reproduces the observed amplitude of primordial perturbations while predicting tensor contributions within current observational bounds. We also demonstrate that the deformation softens the otherwise severe fine-tuning of the quartic self-coupling in minimally coupled inflation. The parameter range γO(103)\gamma \sim \mathcal{O}(10^{-3})-O(102)\mathcal{O}(10^{-2}) emerges as phenomenologically viable, providing a natural extension of Starobinsky inflation compatible with present data. We conclude that marginally deformed R2R^{2} inflation remains a compelling and testable candidate for the primordial dynamics of the Universe, with future CMB and gravitational-wave observations expected to further probe its parameter space.
Nowadays, creation of the tagged corpora is becoming one of the most important tasks of Natural Language Processing (NLP). There are not enough tagged corpora to build machine learning models for the low-resource Uzbek language. In this paper, we tried to fill that gap by developing a novel Part Of Speech (POS) and syntactic tagset for creating the syntactic and morphologically tagged corpus of the Uzbek language. This work also includes detailed description and presentation of a web-based application to work on a tagging as well. Based on the developed annotation tool and the software, we share our experience results of the first stage of the tagged corpus creation
We investigate gravitational quasinormal modes of the Dymnikova black hole, a regular spacetime in which the central singularity is replaced by a de Sitter core. This geometry, originally proposed as a phenomenological model, also arises naturally in the framework of Asymptotically Safe gravity, where quantum corrections lead to a scale-dependent modification of the Schwarzschild solution. Focusing on axial gravitational perturbations, we compute the dominant quasinormal frequencies using the WKB method with Padé approximants and verify the results with time-domain integration. We find that the introduction of the quantum parameter lcrl_{\rm cr} leads to systematic deviations from the Schwarzschild spectrum: the real oscillation frequency decreases as lcrl_{\rm cr} increases, while the damping rate also becomes smaller, implying longer-lived modes. In the limit of large lcrl_{\rm cr}, the quasinormal spectrum smoothly approaches the Schwarzschild case. These results suggest that even though the corrections are localized near the horizon, they leave imprints in the gravitational-wave ringdown which may become accessible to observation with future high-precision detectors.
Recent measurements from the Atacama Cosmology Telescope (ACT), particularly when combined with DESI baryon acoustic oscillation data, have reported a scalar spectral index nsn_s slightly higher than that inferred by {\it Planck}~2018, suggesting a mild tension with the predictions of standard inflationary attractor models. In this work, we revisit the quantum-corrected Higgs inflation scenario within the framework of a non-minimally coupled scalar field theory. Starting from the one-loop effective action, we incorporate radiative corrections through the anomalous scaling parameter AI{\bf A_I} and derive analytic expressions for the inflationary observables nsn_s and rr in the Einstein frame. Our analysis demonstrates that quantum corrections naturally shift nsn_s toward higher values while keeping the tensor-to-scalar ratio rr suppressed. For N=60{\cal N} = 60, the model predicts ns0.9743n_s \simeq 0.9743 and r5.4×103r \simeq 5.4\times10^{-3}, in excellent agreement with the latest ACT+DESI (P-ACT-LB) data and fully consistent with the \textit{Planck}~2018 limit r < 0.036. The derived constraint 4.36\times10^{-10} < \lambda/\xi^{2} < 10.77\times10^{-10} confirms the robustness of the quantum-corrected Higgs framework and indicates that near-future CMB polarization experiments such as CORE, AliCPT, LiteBIRD, and CMB-S4 will be able to probe the predicted parameter space with high precision.
We address the equilibrium configurations and stability properties of anisotropic compact stars whose interior is described by a modified Chaplygin gas (MCG) equation of state in the framework of the regularized four-dimensional Einstein-Gauss-Bonnet (4DEGB) theory. Applying a quasi-local prescription for the pressure anisotropy, we derive the modified Tolman-Oppenheimer-Volkoff (TOV) equations and integrate them numerically over a large parameter space in the Gauss-Bonnet coupling α\alpha and the degree of anisotropy β\beta. We provide mass-radius sequences, mass-compactness, energy density, and pressure profiles, and perform a full stability analysis based on the turning-point criterion, the radial adiabatic index γr\gamma_r, and the radial and transverse sound speeds vr2v_r^2 and vt2v_t^2. Our results show that positive α\alpha and positive anisotropy (β>0)(\beta > 0) systematically increase the maximum mass and radius, enabling then configurations that exceed 2M2\,M_\odot while still obeying causality and the modified Buchdahl bound in 4DEGB gravity. A comparison with the latest astrophysical constraints (NICER, GW170817, GW190814, and massive-pulsar measurements) identifies regions of the (α,β)(\alpha,\beta) parameter space that are observationally allowable. In conclusion, anisotropic dark-energy stars in 4DEGB gravity provide viable, observationally testable ultra-compact alternatives to normal neutron stars and black holes, and also potentially open rich avenues for further multi-messenger searches for higher-curvature effects.
In this work influence of gate extension, channel doping level, and channel thickness to short channel effects- DIBL effect and subthreshold swing, SS for the planar and vertical junctionless field effect transistors is compared. It is shown in the considered range of doping level and channel thickness the DIBL effect is less for junctionless vertical field effect transistors.
In this work influence of gate extension, channel doping level, and channel thickness to short channel effects- DIBL effect and subthreshold swing, SS for the planar and vertical junctionless field effect transistors is compared. It is shown in the considered range of doping level and channel thickness the DIBL effect is less for junctionless vertical field effect transistors.
In this work, we investigate static configurations of dark energy stars within the framework of Rastall-Rainbow (R-R) gravity, which combines an energy-dependent deformation of spacetime with a nonminimal coupling between matter and geometry. We begin by deriving the modified field equations corresponding to R-R gravity and subsequently reformulate the stellar structure equations to describe hydrostatic equilibrium. The generalized Tolman-Oppenheimer-Volkoff (TOV) equations are then solved numerically by adopting the modified Chaplygin equation of state to model the interior matter distribution. The R-R parameters, along with fluid constants, are shown to influence the maximum mass, radii, and stiffness of the star sequences compared to the baseline set by general relativity. We apply observational benchmarks from high-mass pulsars and binary-merger events (e.g., GW170817 and GW190814) to appraise viability within the explored parameter space. The results collectively suggest that stable, causal configurations arise from physically meaningful parameter selections, with deviations from general relativity leading to systematic changes in structural characteristics while adhering to theoretical limits. These findings illustrate that Rastall-Rainbow gravity can support stable, observationally consistent dark energy stars, providing verifiable signatures in strong gravitational fields.
Motivated by anomalies in cosmic microwave background observations, we investigate the implications of f(Q,T)f(Q, T) gravity in Bianchi type-I spacetime, aiming to characterize the universe's spatially homogeneous and anisotropic properties. By using a linear combination of non-metricity QQ and the energy-momentum tensor trace TT, we parametrize the deceleration parameter and derive the Hubble solution, which we then impose in the Friedmann equations of f(Q,T)f(Q, T) gravity. Bayesian analysis is employed to find the best-fit values of model parameters, with 1σ1-\sigma and 2σ2-\sigma contour plots illustrating the constraints from observational data, including H(z)H(z) data and the Pantheon+ sample. Our analysis reveals a transition from a decelerated to an accelerated expansion phase, with the present deceleration parameter indicating an accelerating universe. The energy density gradually decreases over time, approaching zero for the present and future, indicating continuous expansion. The anisotropic pressure, initially notably negative, transitions to slightly negative values, suggesting the presence of dark energy. The evolving equation of state parameter ω\omega exhibits behavior akin to phantom energy, influenced by spacetime anisotropy. Violations of the null energy condition and the strong energy condition imply phantom-like behavior and accelerated expansion.
Text classification is an important task in Natural Language Processing (NLP), where the goal is to categorize text data into predefined classes. In this study, we analyse the dataset creation steps and evaluation techniques of multi-label news categorisation task as part of text classification. We first present a newly obtained dataset for Uzbek text classification, which was collected from 10 different news and press websites and covers 15 categories of news, press and law texts. We also present a comprehensive evaluation of different models, ranging from traditional bag-of-words models to deep learning architectures, on this newly created dataset. Our experiments show that the Recurrent Neural Network (RNN) and Convolutional Neural Network (CNN) based models outperform the rule-based models. The best performance is achieved by the BERTbek model, which is a transformer-based BERT model trained on the Uzbek corpus. Our findings provide a good baseline for further research in Uzbek text classification.
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In this work, we study metric-Palatini gravity extended by the antisymmetric part of the affine curvature. This gravity theory leads to general relativity plus a geometric Proca field. Using our previous construction of its static spherically-symmetric AdS solution [Eur. Phys. J. C83 (2023) 4, 318], we perform a detailed analysis in this work using the observational quasiperiodic oscillations (QPOs) data. To this end, we use the latest data from stellar-mass black hole GRO J1655-40, intermediate-mass black hole in M82-X1, and the super-massive black hole in SgA* (our Milky Way) and perform a Monte-Carlo-Markov-Chain (MCMC) analysis to determine or bound the model parameters. Our results shed light on the allowed ranges of the Proca mass and other parameters. The results imply that our solutions can cover all three astrophysical black holes. Our analysis can also be extended to more general metric-affine gravity theories.
In this paper, we investigate the freezing quintessence scenario in late-time cosmic expansion using a non-linear f(R,Lm)f(R, L_m) gravity model, f(R,Lm)=R2+Lmαf(R,L_m)=\frac{R}{2}+L_m^\alpha, where α\alpha is a free parameter. We consider a solution for this model using an appropriate parametrization of the scale factor, and then the model is constrained by observational datasets, including CC, Pantheon+ (SN), and CC+SN+BAO. Our analysis yields results aligning closely with observational data. The Hubble parameter, deceleration parameter, matter-energy density, and EoS parameter of our model exhibit expected trends over cosmic time, supporting its physical validity. Furthermore, the model demonstrates consistency with the Λ\LambdaCDM model in late times, displaying freezing behavior in the ωω\omega - \omega' plane and stability against density perturbations. Our findings suggest that the modified f(R,Lm)f(R, L_m) gravity model is a credible approach to describing the universe's accelerating phase.
In this paper, we investigate the effects of varying bulk viscosity coefficients ζ(t)=ζ0+ζ1H\zeta(t)=\zeta_{0}+\zeta_{1}H on cosmic evolution within the framework of f(T)f(T) teleparallel gravity. We focus on two cases: (i) ζ10\zeta_{1} \neq0 and (ii) ζ1=0\zeta_{1} =0, deriving the Hubble parameter HH as a function of redshift zz using a linear f(T)f(T) model (f(T)=αTf(T) = \alpha T where α0\alpha \neq 0). Using the combined H(z)+Pantheon++BAOH(z)+Pantheon^{+}+BAO dataset, we obtain observational constraints on model parameters. For Case I (ζ10\zeta_1 \neq 0), best-fit values are H0=60.01.9+2.0H_0=60.0^{+2.0}_{-1.9} km/s/Mpc, α=1.010.098+0.10\alpha=1.01^{+0.10}_{-0.098}, ζ0=40.12.0+1.9\zeta_0=40.1^{+1.9}_{-2.0}, and ζ1=0.1230.088+0.093\zeta_1=0.123^{+0.093}_{-0.088}, while for Case II (ζ1=0\zeta_1 = 0), they are H0=67.51.3+1.3H_0=67.5^{+1.3}_{-1.3} km/s/Mpc, α=0.940.13+0.14\alpha=0.94^{+0.14}_{-0.13}, and ζ0=34.72.0+2.0\zeta_0=34.7^{+2.0}_{-2.0}. The analysis reveals a transition in the deceleration parameter, indicating a shift from deceleration to acceleration of the universe's expansion, with present-day values of q00.49q_{0} \approx -0.49 and q00.32q_{0} \approx -0.32 for the respective cases. The jerk parameter j(z)j(z) and effective EoS for the cosmic viscous fluid also support the cosmic acceleration, with trajectories aligning with the quintessence scenario. These findings underscore the potential of our f(T)f(T) model dominated by bulk viscous matter in explaining cosmic acceleration.
In this manuscript, we investigate the constraints on dynamical vacuum models within the framework of Λ(t)\Lambda(t)CDM cosmology by assuming a parameterization of the vacuum energy density as ρΛ(t)=ρΛ0[1+α(1a)]\rho_{\Lambda}(t)=\rho_{\Lambda 0} \left[1 + \alpha (1 - a)\right], where ρΛ0\rho_{\Lambda 0} is the present vacuum density and α\alpha is a free parameter. We use 31 cosmic chronometer data points and 1048 Pantheon type Ia supernova samples to constrain the model parameters. Our statistical analysis employs Markov Chain Monte Carlo (MCMC) simulations. We have found that the universe is currently undergoing accelerated expansion, transitioning from a decelerating phase. The transition redshift zt=0.650.19+0.03z_t=0.65^{+0.03}_{-0.19} obtained from the combined CC+SNe dataset is consistent with recent constraints. The total EoS indicates an accelerating phase, with density parameters for matter and vacuum energy exhibiting expected behaviors. The Om(z)Om(z) diagnostic shows distinct behaviors for different datasets, and the present value of the jerk parameter deviates slightly from the Λ\LambdaCDM model but remains consistent within uncertainties. These findings support the dynamic nature of dark energy and provide valuable constraints on the evolution of the universe.
In the generalized matter-geometry coupling theory, we investigate the physical characteristics and causality of some new cosmological models for a flat, homogeneous, and isotropic spacetime filled with stiff, radiation, dust, and curvature fluid sources. We obtain a particular cosmological model corresponding to each source fluid, called Models I, II, III, and IV, respectively. We make observational constraints on each model using the joint analysis of 3131 Cosmic Chronometer (CC) Hubble dataset and 17011701 Pantheon+SH0ES datasets to estimate the current values of model parameters. Using these statistical results, we have analyzed the information criteria, effective EoS parameter, causality of the models, and viability of this generalized gravity theory. Subsequently, we investigate the effective equation of state and deceleration parameter for each model. We found that all models in the late-time universe exhibit transit-phase acceleration, and Models I and II show both the early as well as late-time accelerating phase of the expanding universe. We found the current values of the deceleration parameter in the range 0.8857q00.4279-0.8857\le q_{0}\le-0.4279 with transition redshift 0.4867zt0.8390.4867\le z_{t}\le0.839 and the effective EoS parameter in the range 0.9238ωeff0.6186-0.9238\le\omega_{eff}\le-0.6186. We analyzed the square sound speed condition cs2c2c_{s}^{2}\le c^{2} for each model.
We investigate the divergence-free parametric form of the deceleration parameter within the simplest non-minimal matter-geometry coupling in f(R,T)f(R,T) gravity, where RR is the Ricci scalar and TT is the trace of the energy-momentum tensor. Specifically, we consider the linear model $f(R,T) = R + 2\lambda T,where, where \lambda$ governs the interaction between matter and geometry. Using this parametric form, we derive the Hubble parameter as a function of redshift zz and incorporate it into the modified Friedmann equations. Constraining the model with OHD and Pantheon data, we obtain precise estimates for H0H_0, the present deceleration parameter q0q_0, and its evolutionary component q1q_1, confirming a smooth transition between cosmic deceleration and acceleration. Further, we analyze the evolution of the energy density ρ\rho and total EoS parameter ω\omega for different λ\lambda values, highlighting deviations from Λ\LambdaCDM and the role of λ\lambda in shaping cosmic dynamics. In addition, we examine energy conditions, finding that the NEC and DEC are satisfied throughout evolution, while the SEC is violated at late times, supporting the observed acceleration. Our findings demonstrate that this divergence-free parameterization within f(R,T)f(R,T) gravity offers a viable framework for explaining late-time cosmic acceleration while maintaining key observational and theoretical constraints.
In this study, we explore the impact of the interacting parameter on dark matter in a model resulting from a parametrization of dark energy density. To ensure a model-independent approach, we treat rd r_d as a free parameter, avoiding assumptions about the physics of the early Universe or specific recombination models. This approach allows late-time cosmological observations to directly constrain rd r_d along with other parameters. Using recent measurements from the Dark Energy Spectroscopic Instrument (DESI) Year 1, cosmic chronometers (CC) and Pantheon+^{+} supernova (SNe Ia) data, we uncover a significant effect of the interacting parameter on dark matter. Our analysis reveals that while non-interacting models attribute 68.2\% of the cosmic energy density to dark energy, interacting models increase this share to 73.4\%. To further probe these differences, we evaluate the evolution of the deceleration parameter for each model, contrasting them against the Λ\LambdaCDM paradigm and observational data from CC and SNe Ia measurements. Finally, we apply various statistical metrics to rigorously assess the performance of these models.
This work investigates a single-field inflationary model, a specific class of the K-essence models where a coupling term exists between canonical Lagrangian and the potential. This coupling term has many effects on key inflationary parameters consisting of the power spectral, the spectral index, the tensor-to-scalar ratio, the Hubble parameter, the equation of state parameter, and the slow-roll parameter. By solving the equations numerically and deriving analytical results, how this modification affects inflationary dynamics can be analyzed. Our results show that the coupling term, α\alpha, decreases the inflationary parameters, such as the tensor-to-scalar ratio, rr, and improves the consistency with observational constraints from Planck and BICEP/Keck at the 68%68 \% and 95%95 \% confidence. These findings indicate that the studied model provides a promising alternative to the early universe dynamics while aligning with recent cosmological observations.
We are experiencing a golden age of experimental cosmology, with exact and accurate observations being used to constrain various gravitational theories like never before. Alongside these advancements, energy conditions play a crucial theoretical role in evaluating and refining new proposals in gravitational physics. We investigate the energy conditions (WEC, NEC, DEC, and SEC) for two f(Q,Lm)f(Q, L_m) gravity models using the FLRW metric in a flat geometry. Model 1, f(Q,Lm)=αQ+2Lm+βf(Q, L_m) = -\alpha Q + 2L_m + \beta, features linear parameter dependence, satisfying most energy conditions while selectively violating the SEC to explain cosmic acceleration. The EoS parameter transitions between quintessence, a cosmological constant, and phantom energy, depending on α\alpha and β\beta. Model 2, $f(Q, L_m) = -\alpha Q + \lambda (2L_m)^2 + \beta$, introduces nonlinearities, ensuring stronger SEC violations and capturing complex dynamics like dark energy transitions. While Model 1 excels in simplicity, Model 2's robustness makes it ideal for accelerated expansion scenarios, highlighting the potential of f(Q,Lm)f(Q, L_m) gravity in explaining cosmic phenomena.
We formulate and analyze a new class of electrically charged black hole (BH) solutions in Lorentz-violating gravity, where nonlinear ModMax electrodynamics is nonminimally coupled to a Kalb-Ramond (KR) two-form field. The spontaneous breaking of local Lorentz symmetry is triggered by a nonzero vacuum expectation value of the KR field, characterized by a small dimensionless parameter \ell. To incorporate both standard and phantom sectors, we introduce a discrete sign-flip parameter ζ=±1\zeta = \pm1, which flips the gauge-kinetic terms in the phantom (ζ=1\zeta = -1) branch. Assuming a vanishing cosmological constant and a self-interacting potential with minimum V=0V' = 0, we obtain exact analytical solutions for the metric function and electric potential. The resulting spacetime interpolates between Schwarzschild, Reissner-Nordstrom, and ModMax BHs, with curvature scalars showing deviations controlled by (,γ,ζ)(\ell, \gamma, \zeta). We study scalar, electromagnetic, and gravitational perturbations using both frequency-domain (Pade-averaged WKB) and time-domain (Gundlach-Price-Pullin plus Prony) methods. We find that increasing either \ell or the ModMax parameter γ\gamma enhances the real and imaginary parts of QNMs, indicating higher oscillation frequencies and faster damping, especially in the phantom sector. The effective potentials deepen under phantom deformation, supporting more tightly bound modes. Furthermore, we analyze the greybody factors and compute the sparsity η\eta of Hawking radiation, which quantifies the nonthermal character of particle emission. We show that η\eta is significantly affected by \ell, decreasing with increasing Lorentz violation and asymptotically approaching a scaled version of the Schwarzschild value.
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