arXiv subjects

Rajesh Kumar

Publications and source records attributed to Rajesh Kumar.

At least 91 records · Page 5Linked to original sources

arXiv2023

Dictionary Attack on IMU-based Gait Authentication

We present a novel adversarial model for authentication systems that use gait patterns recorded by the inertial measurement unit (IMU) built into smartphones. The attack idea is inspired by and named after the concept of a dictionary attack on knowledge (PIN or password) based authentication systems. In particular, this work investigates whether it is possible to build a dictionary of IMUGait patterns and use it to launch an attack or find an imitator who can actively reproduce IMUGait patterns that match the target's IMUGait pattern. Nine physically and demographically diverse individuals walked at various levels of four predefined controllable and adaptable gait factors (speed, step length, step width, and thigh-lift), producing 178 unique IMUGait patterns. Each pattern attacked a wide variety of user authentication models. The deeper analysis of error rates (before and after the attack) challenges the belief that authentication systems based on IMUGait patterns are the most difficult to spoof; further research is needed on adversarial models and associated countermeasures.

cs.CR↗

arXiv2023

An Eternal gravitational collapse in $f(R)$ theory of gravity and their astrophysical implications

In this work, we explore the eternal collapsing phenomenon of a stellar system (e.g., a star) within the framework of $f(R)$ gravity and investigate some new aspects of the continued homogeneous gravitational collapse with perfect fluid distribution. The exact solutions of field equations have been obtained in an independent way by the parameterization of the expansion scalar ($Θ$) governed by the interior spherically symmetric FLRW metric. We impose the Darmois junction condition required for the smooth matching of the interior region to the Schwarzschild exterior metric across the boundary hypersurface of the star. The junction conditions demand that the pressure is non-vanishing at the boundary and is proportional to the non-linear terms of $f(R)$ gravity, and the mass function $m(t, r)$ is equal to Schwarzschild mass $M$. The eight massive stars, namely $Westerhout 49-2, BAT99-98, R136a1, R136a2, WR 24, Pismis 24-1$, $λ- Cephei$, and $β-Canis Majoris$ with their known astrophysical data (masses and radii) are used to estimate the numerical values of the model parameters which allows us to study the solutions numerically and graphically. Here we have discussed two $f(R)$ gravity models describing the collapse phenomenon. The singularity analysis of models is discussed via the apparent horizon and we have shown that stars tend to collapse for an infinite co-moving time in order to attain the singularity (an eternal collapsing phenomenon). We have also shown that our models satisfy the energy conditions and stability requirements for stellar systems.

gr-qc↗

arXiv2023

Spotting Fake Profiles in Social Networks via Keystroke Dynamics

Spotting and removing fake profiles could curb the menace of fake news in society. This paper, thus, investigates fake profile detection in social networks via users' typing patterns. We created a novel dataset of 468 posts from 26 users on three social networks: Facebook, Instagram, and X (previously Twitter) over six sessions. Then, we extract a series of features from keystroke timings and use them to predict whether two posts originated from the same users using three prominent statistical methods and their score-level fusion. The models' performance is evaluated under same, cross, and combined-cross-platform scenarios. We report the performance using k-rank accuracy for k varying from 1 to 5. The best-performing model obtained accuracies between 91.6-100% on Facebook (Fusion), 70.8-87.5% on Instagram (Fusion), and 75-87.5% on X (Fusion) for k from 1 to 5. Under a cross-platform scenario, the fusion model achieved mean accuracies of 79.1-91.6%, 87.5-91.6%, and 83.3-87.5% when trained on Facebook, Instagram, and Twitter posts, respectively. In combined cross-platform, which involved mixing two platforms' data for model training while testing happened on the third platform's data, the best model achieved accuracy ranges of 75-95.8% across different scenarios. The results highlight the potential of the presented method in uncovering fake profiles across social network platforms.

cs.SI↗

arXiv2023

Black hole formation in gravitational collapse and their astrophysical implications

In this work, we have investigated a novel aspect of black hole (BH) formation during the collapse of a self-gravitating configuration. The exact solution of the Einstein field equations is obtained in a model-independent way by considering a parametrization of the expansion scalar ($Θ$) in the background of spherically symmetric space-time geometry governed by the FLRW metric. Smooth matching of the interior solution with the Schwarzschild exterior metric across the boundary hypersurface of the star, together with the condition that the mass function $m(t,r)$ is equal to Schwarzschild mass $M$, is used to obtain all the physical and geometrical parameters in terms of the stellar mass. The four known massive stars namely $R136a3$, $Melnick$, $R136c$, and $R136b$ with their known astrophysical data (mass, radius, and present age) are used to study the physics of the model both numerically and graphically. We demonstrate that the formation of the apparent horizon occurs earlier than the singular state that is, the model of massive stars would inevitably lead to the formation of a BH as their end state. We have conducted an analysis indicating that the lifespans of massive stars are closely related to their respective masses. Our findings demonstrate that more massive stars exhibit considerably shorter lifespans in comparison to their lighter counterparts. Thus, the presented model corresponds to the evolutionary stages of astrophysical stellar objects and theoretically predicts their possible lifespan. We have also shown that our model satisfies the energy conditions and stability requirements via Herrera's cracking method.

gr-qc↗

arXiv2023

Quantitative analysis of collagen remodeling in pancreatic lesions using computationally translated collagen images derived from brightfield microscopy images

The changes in stromal collagen play a crucial role during the pathogenesis and progression of pancreatic intraepithelial neoplasm (PanIN) to pancreatic ductal adenocarcinoma (PDAC) while misdiagnosis of PanIN is common because of the resemblance to chronic pancreatitis (CP) in its symptoms and subsequent evaluations similarities. To visualize fibrillar collagen in tissues, second harmonic generation microscopy is now utilized as a gold standard in various stromal-based research analyses. However, a technical approach that can perform a quantitative analysis of fibrillar collagen directly on standard slides stained with H&E can (i) discard the need for specialized and costly equipment or labels, (ii) further supplement the conventional histopathological insights and, (iii) potentially be integrated within the framework of standard histopathology workflow. In this study, the whole-core brightfield H&E-stained images of pancreatic tissues were translated computationally into the new collagen images. Subsequently, collagen characteristics of PDAC, PanIN, CP, and normal pancreatic tissues (control) were extracted and compared. The highest alignment (p < 0.01, R2 = 0.2594) was observed in PDAC cores in comparison to the remaining three groups, while the lowest fiber density (p < 0.0001, R2 = 0.3569) was observed in case of normal tissue cores. Moreover, the collagen area and fiber length had shown higher area under curve (0.83 and 0.81, respectively) in discriminating neoplastic and non-neoplastic tissues based on their receiver operating characteristics. The study demonstrated that the computationally generated collagen images can provide a quantitative assessment of collagen remodeling in pancreatic lesions. The cross-modality image synthesis may further lead towards better histopathological and tissue microenvironment insights without the need of specialized imaging equipment or labels.

q-bio.QM↗

arXiv2023

Rationally Extended Harmonic Oscillator potential, Isospectral Family and the Uncertainity Relations

We consider the rationally extended harmonic oscillator potential which is isospectral to the conventional one and whose solutions are associated with the exceptional, $X_m$- Hermite polynomials and discuss its various important properties for different even codimension of $m$. The uncertainty relations are obtained for different $m$ and it is shown that for the ground state, the uncertainity increases as $m$ increases. A one parameter $(λ)$ family of exactly solvable isospectral potential corresponding to this extended harmonic oscillator potential is obtained. Special cases corresponding to the $λ=0$ and $λ= -1$, which give the Pursey and the Abhram-Moses potentials respectively, are discussed. The uncertainty relations for the entire isospectral family of potentials for different $m$ and $λ$ are also calculated.

quant-ph↗

arXiv2023

Semi-analytical Solutions for Breakage and Aggregation-breakage Equations via Daftardar-Jafari Method

The semi-analytical method obtains the solution for linear/nonlinear ODEs and PDEs in series form. This article presents a novel semi-analytical approach named Daftardar-Jafari method (DJM) to solve integro-partial differential equation such as breakage and nonlinear aggregation-breakage equations (ABE). Four test cases for the breakage equation are used to acquire closed form series solutions. Further, numerical findings such as number density and moments are compared with the analytical solutions to show the efficiency and accuracy of the method. Moreover, the DJM is employed to solve the well-known ABE, and truncated solutions are presented for the two test cases. In addition, absolute errors over various time periods are depicted in the form of tables.

math.NA↗

arXiv2023

Cosmological implications of an interacting model of dark matter \& dark energy

In this paper, we have studied an interacting dark energy model. We have assumed the gravitational interaction between the matter fields i.e. between barotropic fluid and the dark energy. The dark energy evolution within the framework of spatially homogeneous and isotropic Friedmann-Robertson-Walker space-time. Therefore, we examine the cosmic evolution from the perspective of interacting scenario by selecting a suitable ansatz for the scale factor resulting from a parametrization of Hubble parameter. The evolution of the cosmological parameters are discussed in some details in the considered interacting scenario by calculating parameters and quantities such as deceleration parameter, energy density, pressure, equation of state (EoS) etc. Also, we have performed some cosmological tests and analysis in support of our obtained interacting model. Finally, we reconstruct the potential of the scalar field and refute the refined swampland conjecture using the equation of state of dark energy and the relationship between energy density and pressure with the scalar field and potential, and then thoroughly describe the findings.

gr-qc↗

arXiv2023

Molecular lighting goes less powering

The present era has seen tremendous demands for low-cost electrochromic materials for visible-region multicolor display technology, paper-based, flexible, and wearable electronic devices, smart windows, and optoelectronic applications. Towards this goal, we report large-scale polyelectrochromic devices fabricated on rigid to flexible ITO substrates comprising novel anthracene containing viologen, (1,1'-bis(anthracen-9-ylmethyl)-[4,4'-bipyridine]-1,1'-diium bromide, abbreviated as AnV2+), and polythiophene (P3HT). Inter-estingly, the devices show three states of reversible visible color in response to the applied bias, sub-second to second switching time (0.7 s/1.6 s), and high coloration efficiency (484 cm2/C), longer cycling stability up to 3000 s (103 switching cycles). Thanks to the anthracenes moieties introduced to viologen that inhibit formation of undesired dimer of cation radicals formed in response to the applied bias, other-wise it would hamper the devices reconfiguration. The devices are fully characterized, and electrochromic performances are ensured by bias-dependent UV-Vis, and Raman spectroscopy. The fabricated electro-chromic devices are tested with the commercially available low-cost cells to perform, which is highly de-sired for practical applications. The computational study facilitates the understanding of experimental re-sults. The alternating current (AC)-based electrical impedance spectroscopy reveals that P3HT facilitates reducing charge transfer resistance of the devices. Our work shows CMOS compatibility and one of the best-performing devices that could pave the way for developing cost-effective flexible, and wearable electrochromic devices.

cond-mat.mtrl-sci↗

arXiv2023

Eternal homogeneous gravitational collapse: A comprehensive analysis from $Θ$ parametrization

A new class of self-gravitating collapsing star models with perfect fluid distributions is discussed in this work. The paper has a comprehensive analysis of a homogeneous gravitational collapsing system wherein using a parametrization scheme for the expansion-scalar $(Θ)$, the solutions of the Einstein Field Equations (EFEs) are determined independently. The background geometry for the analysis is considered to be homogeneous and isotropic represented by a Friedmann-Leimatre-Robertson-Walker (FLRW) metric and by employing the boundary conditions, we have discussed the solution in more detail. Further, all the physical and geometrical parameters are obtained in terms of Schwarzschild mass $(M)$ that makes the model significant in astrophysical applications. The singularity analysis of the collapsing system is also discussed by the apparent-horizon, and it has seen that the homogenous gravitational collapse turns into a new kind of scenario- Eternal collapsing object.

gr-qc↗

arXiv2023

Spherically symmetric gravitational collapse in the background of Chaplygin gas

This paper considers the spherically symmetric gravitational collapse in the background of Chaplygin gas as dark energy component. The dark energy is assumed to be generalized and modified Chaplygin gas. The exterior of the star is considered to be Schwarzschild de-sitter/anti-de sitter metric and discusses the junction conditions. We have discussed the singularity formation in both forms of chaplygin gas case and it is obtained that such collapsing fluids favor the formation of black-hole.

gr-qc↗

arXiv2023

Synthesizing Human Gaze Feedback for Improved NLP Performance

Integrating human feedback in models can improve the performance of natural language processing (NLP) models. Feedback can be either explicit (e.g. ranking used in training language models) or implicit (e.g. using human cognitive signals in the form of eyetracking). Prior eye tracking and NLP research reveal that cognitive processes, such as human scanpaths, gleaned from human gaze patterns aid in the understanding and performance of NLP models. However, the collection of real eyetracking data for NLP tasks is challenging due to the requirement of expensive and precise equipment coupled with privacy invasion issues. To address this challenge, we propose ScanTextGAN, a novel model for generating human scanpaths over text. We show that ScanTextGAN-generated scanpaths can approximate meaningful cognitive signals in human gaze patterns. We include synthetically generated scanpaths in four popular NLP tasks spanning six different datasets as proof of concept and show that the models augmented with generated scanpaths improve the performance of all downstream NLP tasks.

cs.HC↗

arXiv2023

Elzaki Transform Based Accelerated Homotopy Perturbation Method for Multi-dimensional Smoluchowski's Coagulation and Coupled Coagulation-fragmentation Equations

This article aims to establish a semi-analytical approach based on the homotopy perturbation method (HPM) to find the closed form or approximated solutions for the population balance equations such as Smoluchowski's coagulation, fragmentation, coupled coagulation-fragmentation and bivariate coagulation equations. An accelerated form of the HPM is combined with the Elzaki transformation to improve the accuracy and efficiency of the method. One of the significant advantages of the technique lies over the classic numerical methods as it allows solving the linear and non-linear differential equations without discretization. Further, it has benefits over the existing semi-analytical techniques such as Adomian decomposition method (ADM), optimized decomposition method (ODM), and homotopy analysis method (HAM) in the sense that computation of Adomian polynomials and convergence parameters are not required. The novelty of the scheme is shown by comparing the numerical findings with the existing results obtained via ADM, HPM, HAM and ODM for non-linear coagulation equation. This motivates us to extend the scheme for solving the other models mentioned above. The supremacy of the proposed scheme is demonstrated by taking several numerical examples for each problem. The error between exact and series solutions provided in graphs and tables show the accuracy and applicability of the method. In addition to this, convergence of the series solution is also the key attraction of the work.

math.NA↗

arXiv2022

$η$ meson in strange magnetized matter

The in-medium properties of $η$ mesons are studied in hot and dense isospin asymmetric strange magnetized matter using the chiral SU(3) hadronic mean-field model. The scalar and vector density of baryons are expressed in terms of thermal distribution functions at finite temperature and magnetic field and have dependence on the scalar fields $σ$, $ζ$, and $δ$ through the effective mass of baryons and the dependence on the vector fields $ω, ρ$, and $ϕ$ through the effective chemical potential. The properties of $η$ mesons get modified in a hot and dense magnetized environment through the medium-modified nucleons and hyperons. The negative mass shift obtained gives rise to optical potential, which is attractive in the medium and suggests a possibility of $η$-mesic bound states formation. The addition of hyperons in the medium enhances the attractive interactions and causes an increased negative mass shift for $η$ mesons.

hep-ph↗

arXiv2022

Existence and density conservation using a non-conservative approximation for Safronov-Dubovski aggregation equation

The paper deals with the global existence and density conservation for the Safronov-Dubovski equation for three different coefficients $ϕ$ such that $ϕ_{i,j} \leq \frac{(i+j)}{\min\{i,j\}}$, $ϕ_{i,j} \leq (i+j)$ and $ϕ_{i,j} \leq (1+i+j)^α$ $\forall$ $i,j \in \mathbb{N}$, $α\in [0,1]$. The non-conservative approximation is applied to study the problem and results such as Helly's selection theorem and the refined version of the De la Vallée-Poussin theorem are implemented to establish the existence of each case of the kernel. The article also focuses on the conditions for the conservation of mass per unit volume for such an equation.

math.AP↗

arXiv2022

Long Range Plan: Dense matter theory for heavy-ion collisions and neutron stars

Since the release of the 2015 Long Range Plan in Nuclear Physics, major events have occurred that reshaped our understanding of quantum chromodynamics (QCD) and nuclear matter at large densities, in and out of equilibrium. The US nuclear community has an opportunity to capitalize on advances in astrophysical observations and nuclear experiments and engage in an interdisciplinary effort in the theory of dense baryonic matter that connects low- and high-energy nuclear physics, astrophysics, gravitational waves physics, and data science

nucl-th↗

arXiv2022

Convergence and error analysis for pure collisional breakage equation

Collisional breakage in the particulate process has a lot of recent curiosity. We study the pure collisional breakage equation which is nonlinear in nature accompanied by locally bounded breakage kernel and collision kernel. The continuous equation is discretized using a finite volume scheme (FVS) and the weak convergence of the approximated solution towards the exact solution is analyzed for non-uniform mesh. The idea of the analysis is based on the weak $L^1$ compactness and a suitable stable condition on time step is introduced. Furthermore, theoretical error analysis is developed for a uniform mesh when kernels are taken in $W_{loc}^{1,\infty}$ space. The scheme is shown to be first-order convergent which is verified numerically for three test examples of the kernels.

math.NA↗

arXiv2022

Numerical analysis for coagulation-fragmentation equations with singular rates

This article deals with the convergence of finite volume scheme (FVS) for solving coagulation and multiple fragmentation equations having locally bounded coagulation kernel but singularity near the origin due to fragmentation rates. Thanks to the Dunford-Pettis and De La Vall$\acute{e}$e-Poussin theorems which allow us to have the convergence of numerically truncated solution towards a weak solution of the continuous model using a weak $L^1$ compactness argument. A suitable stable condition on time step is taken to achieve the result. Furthermore, when kernels are in $W^{1,\infty}_{loc}$ space, first order error approximation is demonstrated for a uniform mesh. It is numerically validated by attempting several test problems.

math.NA↗