arXiv subjects

Tanmoy Chowdhury

Publications and source records attributed to Tanmoy Chowdhury.

10 recordsLinked to original sources

arXiv2025

Cosmological model with Gong-Zong Parametrization in $f(R,L_m)$ gravity

We present the cosmic expansion scenarios in the $f(R, L_m)$ gravity studied by using the dark energy equation of state (EoS) parameters. We proceed with the specific form of $f(R, L_m)$ gravity termed as $f(R, L_m)=\frac{R}{2}+L_{m}^α$. We derive the expansion rate in terms of the red-shift for two different forms of EoS parameter. In first model, EoS parameter varies inversely with the redshift and in second model, it involves the exponential form with the redshift. By using the Bayesian methods based on the $χ^{2}$-minimization technique, the median values of model parameters are determined for the cosmic chronometer(CC) and Joint (CC+Pantheon) data sets. The behavior of fundamental cosmological parameters such as the deceleration parameter, energy density and pressure are thoroughly examined. Additionally, the nature of Statefinder diagnostics and the present age of universe exemplifies the compatibility with the late-time astronomical observations.

gr-qc↗

arXiv2025

Study of Wormhole in $f(Q)$ gravity with some dark energy models

This study discusses the development of some particular static wormhole models in the background of an extended $f(Q)$ gravity theory. Wormhole solutions are derived by considering the radial pressure to admit an equation of state corresponding to Chaplygin gas. The Chaplygin gas equation of state is taken into consideration in two different forms: $p_{r}=-\frac{Bb(r)^{u}}{ρ^{a}}$, $p_{r}=-\frac{B}{ρ^{a}}$. Wormhole models are also generated assuming that a variable barotropic fluid may explain the radial pressure given by $p_{r} =-ωρb(r)^u$. For every model, the shape function $b(r)$ is the function that can be derived from the wormhole metric in any scenario. The stability analysis of the wormhole solutions and the shape function viability for each situation are then investigated.Since each wormhole model is shown to violate the null energy condition (NEC), it can be understood that these wormholes are traversable. More generally, we investigate whether the model is stable under the hydrostatic equilibrium state condition using the TOV equation.The physical characteristics of these models are shown under the same energy circumstances. The typical characteristic is the radial pressure $p_{r}$ near the wormhole throat, which violates the NEC $(ρ+P_{r} \geq0)$. In some models, it is possible to meet the NEC at the neck and yet violate the DEC $(ρ- P_{r}\geq0)$. In summary, precise wormhole models may be generated, provided that $(ρ\geq0)$, and there may be a potential breach of the NEC at the wormhole's throat.

gr-qc↗

arXiv2024

Conservative wormholes in generalized $κ(\mathcal{R},\mathcal{T})$-function

We present an exhaustive study of wormhole configurations in $κ(\mathcal{R},\mathcal{T})$ gravity with linear and non-linear functions. The model assumed Morrison-Thorne spacetime where the redshift and shape functions linked with the matter contain and geometry of the spacetime through non-covariant conservation equation of the stress-energy tensor. The first solution was explored assuming a constant redshift function that leads to a wormhole (WH) which is asymptotically non-flat. The remaining solutions were explored in two cases. Firstly, assuming a linear equation of state $p(r)=ωρ(r)$ along with different forms of $κ(\mathcal{R},\mathcal{T})-$function. This proved enough to derive a shape function of the form $b(r)=r_{0}\left(\frac{r_{0}}{r}\right)^{1/ω}$. Secondly, by assuming specific choices of the shape function consistent with the wormhole configuration requirements. All the solutions fulfill flare-out condition, asymptotically flat and supported by phantom energy. Further, the embedding surface and its revolution has been generated using numerical method to see how the length of the throat is affected of the coupling parameters through $κ(\mathcal{R},\mathcal{T})$ function. At the end, we have also calculated the average null energy condition, which is satisfied by all the WH models signifying minimum exotic matter is required to open the WH throats.

gr-qc↗

arXiv2024

Source Localization for Cross Network Information Diffusion

Source localization aims to locate information diffusion sources only given the diffusion observation, which has attracted extensive attention in the past few years. Existing methods are mostly tailored for single networks and may not be generalized to handle more complex networks like cross-networks. Cross-network is defined as two interconnected networks, where one network's functionality depends on the other. Source localization on cross-networks entails locating diffusion sources on the source network by only giving the diffused observation in the target network. The task is challenging due to challenges including: 1) diffusion sources distribution modeling; 2) jointly considering both static and dynamic node features; and 3) heterogeneous diffusion patterns learning. In this work, we propose a novel method, namely CNSL, to handle the three primary challenges. Specifically, we propose to learn the distribution of diffusion sources through Bayesian inference and leverage disentangled encoders to separately learn static and dynamic node features. The learning objective is coupled with the cross-network information propagation estimation model to make the inference of diffusion sources considering the overall diffusion process. Additionally, we also provide two novel cross-network datasets collected by ourselves. Extensive experiments are conducted on both datasets to demonstrate the effectiveness of \textit{CNSL} in handling the source localization on cross-networks.

cs.SI↗

arXiv2024

Domain Specialization as the Key to Make Large Language Models Disruptive: A Comprehensive Survey

Large language models (LLMs) have significantly advanced the field of natural language processing (NLP), providing a highly useful, task-agnostic foundation for a wide range of applications. However, directly applying LLMs to solve sophisticated problems in specific domains meets many hurdles, caused by the heterogeneity of domain data, the sophistication of domain knowledge, the uniqueness of domain objectives, and the diversity of the constraints (e.g., various social norms, cultural conformity, religious beliefs, and ethical standards in the domain applications). Domain specification techniques are key to make large language models disruptive in many applications. Specifically, to solve these hurdles, there has been a notable increase in research and practices conducted in recent years on the domain specialization of LLMs. This emerging field of study, with its substantial potential for impact, necessitates a comprehensive and systematic review to better summarize and guide ongoing work in this area. In this article, we present a comprehensive survey on domain specification techniques for large language models, an emerging direction critical for large language model applications. First, we propose a systematic taxonomy that categorizes the LLM domain-specialization techniques based on the accessibility to LLMs and summarizes the framework for all the subcategories as well as their relations and differences to each other. Second, we present an extensive taxonomy of critical application domains that can benefit dramatically from specialized LLMs, discussing their practical significance and open challenges. Last, we offer our insights into the current research status and future trends in this area.

cs.CL↗

arXiv2024

MIM-Reasoner: Learning with Theoretical Guarantees for Multiplex Influence Maximization

Multiplex influence maximization (MIM) asks us to identify a set of seed users such as to maximize the expected number of influenced users in a multiplex network. MIM has been one of central research topics, especially in nowadays social networking landscape where users participate in multiple online social networks (OSNs) and their influences can propagate among several OSNs simultaneously. Although there exist a couple combinatorial algorithms to MIM, learning-based solutions have been desired due to its generalization ability to heterogeneous networks and their diversified propagation characteristics. In this paper, we introduce MIM-Reasoner, coupling reinforcement learning with probabilistic graphical model, which effectively captures the complex propagation process within and between layers of a given multiplex network, thereby tackling the most challenging problem in MIM. We establish a theoretical guarantee for MIM-Reasoner as well as conduct extensive analyses on both synthetic and real-world datasets to validate our MIM-Reasoner's performance.

cs.SI↗

arXiv2023

Testing of K(R,T)-gravity through gravastar configurations

In this article, we are reporting for the first time the existence of gravastar configurations in the framework of K(R,T)-gravity, which can be treated as an alternative to a black hole (Mazur and Mottola). This strengthens how much this new gravity theory may be physically demanding to the gravity community in the near future. We first develop the gravastar field equations for a generic K(R,T) functional and then we study four different models within this theory. We find that the solutions for the interior region are regular everywhere regardless of the exact form of the K(R,T) functional. The solutions for the shell region indicate that two of the four models subjected to the study are physically feasible. In addition, the junction conditions are considered at each interface by using the Lanczos equations that yield the surface density and pressure at the thin shell. We investigate various characteristics of the gravastar structure such as the proper length, energy, and entropy of the spherical distribution.

gr-qc↗

arXiv2023

Knowledge-enhanced Neural Machine Reasoning: A Review

Knowledge-enhanced neural machine reasoning has garnered significant attention as a cutting-edge yet challenging research area with numerous practical applications. Over the past few years, plenty of studies have leveraged various forms of external knowledge to augment the reasoning capabilities of deep models, tackling challenges such as effective knowledge integration, implicit knowledge mining, and problems of tractability and optimization. However, there is a dearth of a comprehensive technical review of the existing knowledge-enhanced reasoning techniques across the diverse range of application domains. This survey provides an in-depth examination of recent advancements in the field, introducing a novel taxonomy that categorizes existing knowledge-enhanced methods into two primary categories and four subcategories. We systematically discuss these methods and highlight their correlations, strengths, and limitations. Finally, we elucidate the current application domains and provide insight into promising prospects for future research.

cs.AI↗

arXiv2022

Possible existence of stable compact stars in $κ(\mathcal{R},\mathcal{T})-$gravity

We present the first interior solutions representing compact stars in $κ(\mathcal{R},\mathcal{T})$ gravity, by solving the modified field equations in isotropic coordinates. Further, we have assumed the metric potentials in Schwarzschild's form and a few parameters along with the isotropic condition of pressure. For solving, we use specific choice of the running gravitational constant as $κ(\mathcal{R},\mathcal{T})=8π-λ\mathcal{T} ~~(G=\tilde{c}=1)$. Once arrived at the reduced field equations, we investigate two solutions with $c=1$ and $c \neq 1$, where $c$ denotes here another constant that should not be confused with the speed of light. Then, we investigate each solution by determining the thermodynamics variable {\it viz} pressure, density, speed of sound, and adiabatic index. We found that these solutions satisfy the Bondi criterion, causality condition, and energy conditions. We also found that the $M-R$ curves generated from these solutions satisfy the stringent constraints provided by the gravitational wave observations due to the neutron star merger GW 170817.

gr-qc↗

arXiv2022

DeepGAR: Deep Graph Learning for Analogical Reasoning

Analogical reasoning is the process of discovering and mapping correspondences from a target subject to a base subject. As the most well-known computational method of analogical reasoning, Structure-Mapping Theory (SMT) abstracts both target and base subjects into relational graphs and forms the cognitive process of analogical reasoning by finding a corresponding subgraph (i.e., correspondence) in the target graph that is aligned with the base graph. However, incorporating deep learning for SMT is still under-explored due to several obstacles: 1) the combinatorial complexity of searching for the correspondence in the target graph; 2) the correspondence mining is restricted by various cognitive theory-driven constraints. To address both challenges, we propose a novel framework for Analogical Reasoning (DeepGAR) that identifies the correspondence between source and target domains by assuring cognitive theory-driven constraints. Specifically, we design a geometric constraint embedding space to induce subgraph relation from node embeddings for efficient subgraph search. Furthermore, we develop novel learning and optimization strategies that could end-to-end identify correspondences that are strictly consistent with constraints driven by the cognitive theory. Extensive experiments are conducted on synthetic and real-world datasets to demonstrate the effectiveness of the proposed DeepGAR over existing methods.

cs.AI↗