arXiv subjects

Anita Yadav

Publications and source records attributed to Anita Yadav.

9 recordsLinked to original sources

arXiv2026

$Λ_{\rm s}$CDM cosmology from a type-II minimally modified gravity

We integrate $Λ_{\rm s}$CDM, a promising scenario for alleviating cosmological tensions, into VCDM, a type-II minimally modified gravity. This promotes the scenario to a fully predictive model (dubbed $Λ_{\rm s}$VCDM) that specifies the cosmological evolution self-consistently, including through the late-time AdS-to-dS transition epoch. In this theory, an auxiliary scalar field generates an effective cosmological constant with either a constant or a linear potential. This allows an abrupt mirror AdS-to-dS transition via a piecewise-linear potential with a sudden slope change. To remove the associated sudden singularity and ensure stable evolution, we smooth the junction using a blended sigmoid interpolant, obtaining rapid but continuous transitions. We identify two qualitatively distinct smooth mirror AdS-to-dS realisations of $Λ_{\rm s}$: (i) an agitated transition, in which the potential interpolates between equal-magnitude AdS and dS plateaus and $Λ_{\rm s}$ develops a central bump; and (ii) a quiescent transition, in which the potential remains continuous but changes slope across the transition layer, so that $Λ_{\rm s}(a)$ can remain monotone, with possible shallow shoulders, and a central bump is not automatic. Depending on type and sharpness, a finite-width transition can induce a transient accelerated-expansion interval ($\ddot a>0$) around $z\sim 1.5-2$, in addition to present-day acceleration, and, if the background enters a region where $V_{,ϕϕ}>2/3$, a nested super-acceleration episode. These distinct transient histories can imprint signatures on background and perturbation evolution. Our construction enables a self-consistent observational assessment of smooth $Λ_{\rm s}$CDM realisations and motivates multi-probe analyses to test transition dynamics and reassess cosmological tensions.

astro-ph.CO↗

arXiv2025

Investigation of the intrinsic hidden spin texture and spin-state segregation in centrosymmetric monolayer dichalcogenide: effectiveness of the electric-field approach

The emergence of hidden spin polarization in centrosymmetric nonmagnetic crystals due to local symmetry breaking has created new opportunities for potential spintronic applications and for enhancing our understanding of mechanisms to electrically manipulate spin-related phenomena. In this work, we investigate within density functional theory the properties of the hidden spin texture and spin-layer segregation in a prototype centrosymmetric dichalcogenide-monolayer material using an electric-field-based method. This method is shown to yield a precise and robust alternative to traditional layer-projected spin-polarization techniques for obtaining the intrinsic hidden spin textures in such materials. Moreover, it gives access at the same time to the spatial distribution within the monolayer of the individual spin-segregated states responsible for the hidden spin textures, not provided by other techniques. With this approach we determine and study the hidden spin textures of the upper valence bands of the PtTe2 monolayer together with the spatial behavior of the probability densities and spin polarization densities of the corresponding maximally segregated spin states. This combined study enabled by the electric-field method yields new insights into the mechanisms controlling the spin-layer segregation and resulting hidden spin texture in such systems. We also discuss the symmetry rules governing the shape in the Brillouin zone of the hidden spin texture, which can be straightforwardly predicted within the present framework.

cond-mat.mtrl-sci↗

arXiv2025

The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics

The standard model of cosmology has provided a good phenomenological description of a wide range of observations both at astrophysical and cosmological scales for several decades. This concordance model is constructed by a universal cosmological constant and supported by a matter sector described by the standard model of particle physics and a cold dark matter contribution, as well as very early-time inflationary physics, and underpinned by gravitation through general relativity. There have always been open questions about the soundness of the foundations of the standard model. However, recent years have shown that there may also be questions from the observational sector with the emergence of differences between certain cosmological probes. In this White Paper, we identify the key objectives that need to be addressed over the coming decade together with the core science projects that aim to meet these challenges. These discordances primarily rest on the divergence in the measurement of core cosmological parameters with varying levels of statistical confidence. These possible statistical tensions may be partially accounted for by systematics in various measurements or cosmological probes but there is also a growing indication of potential new physics beyond the standard model. After reviewing the principal probes used in the measurement of cosmological parameters, as well as potential systematics, we discuss the most promising array of potential new physics that may be observable in upcoming surveys. We also discuss the growing set of novel data analysis approaches that go beyond traditional methods to test physical models. [Abridged]

astro-ph.CO↗

arXiv2025

$Λ_{\rm s}$CDM cosmology: Alleviating major cosmological tensions by predicting standard neutrino properties

We investigate a two-parameter extension of the $Λ_{\rm s}$CDM model by allowing variations in the effective number of neutrino species $N_{\rm eff}$ and their total mass $\sum m_ν$. Our motivation is twofold: (i) to examine whether $Λ_{\rm s}$CDM retains its success in fitting the data and addressing major cosmological tensions, without suggesting a need for a deviation from the standard model of particle physics, and (ii) to determine whether the data indicate new physics that could potentially address cosmological tensions, either in the post-recombination universe through the late-time mirror AdS-dS transition, or in the pre-recombination universe through modifications in the standard values of $N_{\rm eff}$ and $\sum m_ν$, or both. Within the extended $Λ_{\rm s}$CDM model, referred to as $Λ_{\rm s}$CDM+$N_{\rm eff}$+$\sum m_{\rm ν}$, we find no significant tension when considering the Planck-alone analysis. We observe that incorporating BAO data limits the further success of the $Λ_{\rm s}$CDM extension. However, the weakly model-dependent BAOtr data, along with Planck and Planck+PP\&SH0ES, favor $H_0\sim 73\,{\rm km\, s^{-1}\, Mpc^{-1}}$. In cases where BAOtr dataset is used, the mirror AdS-dS transition is very effective in providing enhanced $H_0$ values, and thus the model requires no significant deviation from the standard value of $N_{\rm eff} = 3.044$. Both the $H_0$ and $S_8$ tensions are effectively addressed, with some compromise in the case of the Planck+BAO dataset. Finally, the upper bounds obtained on $\sum m_ν\lesssim 0.5$~eV are fully compatible with neutrino oscillation experiments. Our findings provide evidence that late-time physics beyond $Λ$CDM, such as $Λ_{\rm s}$CDM, without altering the standard pre-recombination universe, can suffice to alleviate the major cosmological tensions.

astro-ph.CO↗

arXiv2024

Cosmological constraints on $Λ_{\rm s}$CDM scenario in a type II minimally modified gravity

The idea of a rapid sign-switching cosmological constant (mirror AdS-dS transition) in the late universe at $z\sim1.7$, known as the $Λ_{\rm s}$CDM model, has significantly improved the fit to observational data and provides a promising scenario for alleviating major cosmological tensions, such as the $H_0$ and $S_8$ tensions. However, in the absence of a fully predictive model, implementing this fit required conjecturing that the dynamics of the linear perturbations are governed by general relativity. Recent work embedding the $Λ_{\rm s}$CDM model with the Lagrangian of a type II minimally modified gravity known as VCDM has propelled $Λ_{\rm s}$CDM to a fully predictive model, removing the uncertainty related to the aforementioned assumption; we call this new model $Λ_{\rm s}$VCDM. In this work, we demonstrate that not only does $Λ_{\rm s}$CDM fit the data better than the standard $Λ$CDM model, but the new model, $Λ_{\rm s}$VCDM, performs even better in alleviating cosmological tensions while also providing a better fit to the data, including CMB, BAO, SNe Ia, and cosmic shear measurements. Our findings highlight the $Λ_{\rm s}$CDM framework, particularly the $Λ_{\rm s}$VCDM model, as a compelling alternative to the standard $Λ$CDM model, especially by successfully alleviating the $H_0$ tension. Additionally, these models predict higher values for $σ_8$, indicating enhanced structuring, albeit with lower present-day matter density parameter values and consequently reduced $S_8$ values, alleviating the $S_8$ tension as well. This demonstrates that the data are well fit by a combination of background and linear perturbations, both having dynamics differing from those of $Λ$CDM. This paves the way for further exploration of new ways for embedding the sign-switching cosmological constant into other models.

astro-ph.CO↗

arXiv2023

$Λ_{\rm s}$CDM model: A promising scenario for alleviation of cosmological tensions

We present a comprehensive analysis of the $Λ_{\rm s}$CDM model, which explores the recent conjecture suggesting a rapid transition of the Universe from anti-de Sitter vacua to de Sitter vacua (viz., the cosmological constant switches sign from negative to positive) at redshift ${z_\dagger\sim 2}$, inspired by the graduated dark energy (gDE) model. Our analysis shows that, predicting $z_\dagger\approx1.7$, $Λ_{\rm s}$CDM simultaneously addresses the major cosmological tensions of the standard $Λ$CDM model, viz., the Hubble constant $H_0$, the Type Ia Supernovae absolute magnitude $M_{\rm B}$, and the growth parameter $S_8$ tensions, along with other less significant tensions such as the BAO Lyman-$α$ discrepancy.

astro-ph.CO↗

arXiv2023

Relaxing cosmological tensions with a sign switching cosmological constant: Improved results with Planck, BAO, and Pantheon data

We present a further observational analysis of the $Λ_{\rm s}$CDM model proposed in Akarsu et al. [Phys. Rev. D 104, 123512 (2021)]. This model is based on the recent conjecture suggesting the Universe has transitioned from anti-de Sitter vacua to de Sitter vacua (viz., the cosmological constant switches sign from negative to positive), at redshift ${z_\dagger\sim2}$, inspired by the graduated dark energy model proposed in Akarsu et al. [Phys. Rev. D 101, 063528 (2020)]. $Λ_{\rm s}$CDM was previously claimed to simultaneously relax five cosmological discrepancies, namely, the $H_0$, $S_8$, and $M_B$ tensions along with the Ly-$α$ and $ω_{\rm b}$ anomalies, which prevail within the standard $Λ$CDM model as well as its canonical/simple extensions. In the present work, we extend the previous analysis by constraining the model using the Pantheon data (with and without the SH0ES $M_B$ prior) and/or the completed BAO data along with the full Planck CMB data. We find that $Λ_{\rm s}$CDM exhibits a better fit to the data compared to $Λ$CDM, and simultaneously relaxes the six discrepancies of $Λ$CDM, viz., the $H_0$, $M_B$, $S_8$, Ly-$α$, $t_0$, and $ω_{\rm b}$ discrepancies, all of which are discussed in detail. When the $M_B$ prior is included in the analyses, $Λ_{\rm s}$CDM performs significantly better in relaxing the $H_0$, $M_B$, and $S_8$ tensions with the constraint ${z_\dagger\sim1.8}$ even when the Ly-$α$ data (which imposed the $z_\dagger\sim2$ constraint in the previous studies) are excluded. In contrast, the presence of the $M_B$ prior causes only negligible improvements for $Λ$CDM. Thus, the $Λ_{\rm s}$CDM model provides remedy to various cosmological tensions simultaneously, only that the galaxy BAO data hinder its success to some extent.

astro-ph.CO↗

arXiv2021

AdCOFE: Advanced Contextual Feature Extraction in Conversations for emotion classification

Emotion recognition in conversations is an important step in various virtual chat bots which require opinion-based feedback, like in social media threads, online support and many more applications. Current Emotion recognition in conversations models face issues like (a) loss of contextual information in between two dialogues of a conversation, (b) failure to give appropriate importance to significant tokens in each utterance and (c) inability to pass on the emotional information from previous utterances.The proposed model of Advanced Contextual Feature Extraction (AdCOFE) addresses these issues by performing unique feature extraction using knowledge graphs, sentiment lexicons and phrases of natural language at all levels (word and position embedding) of the utterances. Experiments on the Emotion recognition in conversations dataset show that AdCOFE is beneficial in capturing emotions in conversations.

cs.CL↗

arXiv2016

Loop Free Multipath Routing Algorithm

Single path routing that is currently used in the internet routers,is easy to implement as it simplifies the routing tables and packet flow paths. However it is not optimal and has shortcomings in utilizing the network resources optimally, load balancing & fast recovery in case of faults (fault tolerance). The given algorithm resolves all these problems by using all possible multiple paths for transfer of information, while retaining loop-free property. We have proposed a new dynamic loop-free multipath routing algorithm which improves network throughput and network resource utilization, reduces average transmission delay, and is not affected by faults in the links and router nodes. The main idea of this algorithm is to maintain multiple possible next hops for a destination along with weights. At every node, the traffic to a destination is split among multiple next hops in proportion to the estimated weights. The number of multiple next hops also changes depending on the traffic conditions, but it is never less than one.

cs.NI↗