arXiv subjects

Barun Majumder

Publications and source records attributed to Barun Majumder.

At least 19 recordsLinked to original sources

arXiv2023

Lorentz and gauge invariance of quantum space

Motivated by generalized uncertainty principle, we derive a discrete picture of the space that respects Lorentz symmetry as well as gauge symmetry through setting an equivalency between linear GUP correction term and electromagnetic interaction term in Dirac equation. We derived a wavefunction solution that satisfies this equivalency. This discreteness may explain the crystal and quasicrystal structures observed in nature at different energy scales.

physics.gen-ph↗

arXiv2022

Quantum Thermodynamics of a Quantum Sized AdS Black Hole

In this paper, we investigate the effects of non-perturbative quantum gravitational corrections on a quantum sized AdS black hole. It will be observed that these non-perturbative quantum gravitational corrections modify the stability of this black hole. We will use the non-equilibrium quantum thermodynamics to investigate the evaporation of this black hole between two states. We will analyze the effects of non-perturbative quantum gravitational corrections on this non-equilibrium quantum thermodynamics. We will explicitly obtain the quantum work distribution for this black hole, as it evaporates between two states. It will be observed that this quantum work distribution is modified due to non-perturbative quantum gravitational corrections.

gr-qc↗

arXiv2021

Quantum Gravity Corrections to the Mean Field Theory of Nucleons

In this paper, we analyze the correction to the mean field theory potential for a system of nucleons. It will be argued that these corrections can be obtained by deforming the Schrödinger's equation describing a system of nucleons by a minimal length in the background geometry of space-time. This is because such a minimal length occurs due to quantum gravitational effects, and modifies the low energy quantum mechanical systems. In fact, as the mean field potential for the nucleons is represented by the Woods-Saxon potential, we will explicitly analyze such corrections to this potential. We will obtain the corrections to the energy eigenvalues of the deformed Schrödinger's equation for the Woods-Saxon potential. We will also construct the wave function for the deformed Schrödinger's equation.

physics.gen-ph↗

arXiv2021

An Analytical 2-D Model of Triple Metal Double Gate Graded Channel Junctionless MOSFET with Hetero-dielectric Gate Oxide Stack

In this paper, a two-dimensional analytical model of a laterally graded-channel triple-metal double-gate Junctionless Field Effect Transistor with hetero dielectric gate oxide stack consisting of SiO$_2$ and HfO$_2$ is derived. The model illustrates higher drive current and better performance against hazardous SCEs and HCEs in below 30 nm regime. Parabolic approximation method is used here to construct channel potentials and electric fields by solving 2-D Poisson's equation with applicable boundary conditions. The basic central and surface potentials as well as central and surface electric fields are being illustrated, Threshold voltage, DIBL, sub-threshold swing (SS) and a compact current model have also been deduced. These parameters clearly show the benefits of proposed graded-channel triple-metal double-gate structure with hetero-dielectric gate oxide stack. The device has reliability in low power applications because of its better Ion and Ioff control. Finally, the analytical model is validated with self-consistent numerical calculations to illustrate better performance of among available junctionless devices.

cond-mat.mtrl-sci↗

arXiv2021

Discreteness of Space from Anisotropic Spin-Orbit Interaction

Various approaches to Quantum Gravity suggest an existence of a minimal measurable length. The cost to have such minimal length could be modified uncertainty principle, modified dispersion relation, non-commutative geometry or breaking of continuous Lorentz symmetry. In this paper, we propose that minimal length can be obtained naturally through spin-orbit interaction. We consider Dresselhaus anisotropic spin-orbit interaction as the perturbative Hamiltonian. When applied to a particle, it implies that the space, which seizes this particle, should be quantized in terms of units that depend on particle's mass. This suggests that all measurable lengths in the space are quantized in units depending on existent mass and the Dresselhaus coupling constant. On one side, this indicates a breakdown of the space continuum picture near the scale of tabletop experiments, and on the other side, it proposes that spin-orbit interaction is a possible quantum gravity effect at low energy scale that leads naturally to space quantization.

gr-qc↗

arXiv2017

I-Love-Q Relations for Neutron Stars in dynamical Chern Simons Gravity

Neutron stars are ideal to probe, not only nuclear physics, but also strong-field gravity. Approximate universal relations insensitive to the star's internal structure exist among certain observables and are useful in testing General Relativity, as they project out the uncertainties in the equation of state. One such set of universal relations between the moment of inertia $(I)$, the tidal Love number and the quadrupole moment $(Q)$ has been studied both in General Relativity and in modified theories. In this paper, we study the relations in dynamical Chern-Simons gravity, a well-motivated, parity-violating effective field theory, extending previous work in various ways. First, we study how projected constraints on the theory using the I-Love relation depend on the measurement accuracy of $I$ with radio observations and that of the Love number with gravitational-wave observations. Provided these quantities can be measured with future observations, we find that the latter could place bounds on dynamical Chern-Simons gravity that are six orders of magnitude stronger than current bounds. Second, we study the I-Q and Q-Love relations in this theory by constructing slowly-rotating neutron star solutions to quadratic order in spin. We find that the approximate universality continues to hold in dynamical Chern-Simons gravity, and in fact, it becomes stronger than in General Relativity, although its existence depends on the normalization of the dimensional coupling constant of the theory. Finally, we study the variation of the eccentricity of isodensity contours inside a star and its relation to the degree of universality. We find that, in most cases, the eccentricity variation is smaller in dynamical Chern-Simons gravity than in General Relativity, providing further support to the idea that the approximate self-similarity of isodensity contours is responsible for universality.

gr-qc↗

arXiv2016

A question mark on the equivalence of Einstein and Jordan frames

With an explicit example, we show that Jordan frame and the conformally transformed Einstein frames clearly lead to different physics for a non-minimally coupled theory of gravity, namely Brans-Dicke theory, at least at the quantum level. The example taken up is the spatially flat Friedmann cosmology in Brans-Dicke theory.

gr-qc↗

arXiv2015

Gravitational Collapse in Gravity's Rainbow

In this paper, we will analyze the gravitational collapse in the framework of gravity's rainbow. We will demonstrate that the position of the horizon for a particle inside the black hole depends on the energy of that particle. It will also be observe that the position of the horizon for a particle falling radially into the black hole also depends on its energy. Thus, it is possible for a particle coming from outside to interact with a particle inside the black, and take some information outside the black hole. This is because for both these particles the position of horizon is different. So, even though the particle from inside the black hole is in its own horizon, it is not in the horizon of the particle coming from outside. Thus, we will demonstrate that in gravity's rainbow information can get out of a black hole.

gr-qc↗

arXiv2015

Improved Universality in the Neutron Star Three-Hair Relations

No-hair like relations between the multipole moments of the exterior gravitational field of neutron stars have recently been found to be approximately independent of the star's internal structure. This approximate, equation-of-state universality arises after one adimensionalizes the multipole moments appropriately, which then begs the question of whether there are better ways to adimensionalize the moments to obtain stronger universality. We here investigate this question in detail by considering slowly-rotating neutron stars both in the non-relativistic limit and in full General Relativity. We find that there exist normalizations that lead to stronger equation-of-state universality in the relations among the moment of inertia and the quadrupole, octopole and hexadecapole moments of neutron stars. We determine the optimal normalization that minimizes the equation-of-state dependence in these relations. The results found here may have applications in the modeling of X-ray pulses and atomic line profiles from millisecond pulsars with NICER and LOFT.

gr-qc↗

arXiv2015

Incorporation of Generalized Uncertainty Principle into Lifshitz Field Theories

In this paper, we will incorporation the generalized uncertainty principle into field theories with Lifshitz scaling. We will first construct both bososnic and fermionic theories with Lifshitz scaling based on generalized uncertainty principle. After that we will incorporate the generalized uncertainty principle into an non-abelian gauge theory with Lifshitz scaling. We will observe that even though the action for this theory is non-local, it is invariant under local gauge transformations. We will also perform the stochastic quantization of this Lifshitz fermionic theory based generalized uncertainty principle.

hep-th↗

arXiv2014

Absence of an Effective Horizon for Black Holes in Gravity's Rainbow

We argue that the divergence in time for the asymptotic observer occurs because of specifying the position of the Horizon beyond the Planck scale. In fact, a similar divergence in time will also occur for an in-going observer in Gravity's Rainbow, if we again specify the position of the Horizon beyond the Planck scale. On the other hand, if we accept the occurrence of a minimum measurable length scale associated with a universal invariant maximum energy scale in Gravity's Rainbow, then the time taken by both the in-going and asymptotic observers will be finite.

gr-qc↗

arXiv2014

Electric Charges and Magnetic Monopoles in Gravity's Rainbow

In this work, we explore the possibility that quantum fluctuations induce an electric or magnetic charge or both, in the context of Gravity's Rainbow. A semi-classical approach is adopted, where the graviton one-loop contribution to a classical energy in a background spacetime is computed through a variational approach with Gaussian trial wave functionals. The energy density of the graviton one-loop contribution, in this context, acts as a source for the electric/magnetic charge. The ultraviolet (UV) divergences, which arise analyzing this procedure, are kept under control with the help of an appropriate choice of the Rainbow's functions. In this way we avoid the introduction of any regularization/renormalization scheme. A comparison with the observed data lead us to determine the size of the electron and of the magnetic monopole which appear to be of Planckian size. Both results seem to be of the same order for a Schwarzschild and a de Sitter background, respectively. Estimates on the magnetic monopole size have been done with the help of the Dirac quantization procedure. We find that the monopole radius is larger than the electron radius. Even in this case the ratio between the electric and magnetic monopole radius appears to be of the same order for both geometries.

gr-qc↗

arXiv2014

Naked Singularities are not Singular in Distorted Gravity

We compute the Zero Point Energy (ZPE) induced by a naked singularity with the help of a reformulation of the Wheeler-DeWitt equation. A variational approach is used for the calculation with Gaussian Trial Wave Functionals. The one loop contribution of the graviton to the ZPE is extracted keeping under control the UltraViolet divergences by means of a distorted gravitational field. Two examples of distortion are taken under consideration: Gravity's Rainbow and Noncommutative Geometry. Surprisingly we find that the ZPE is no more singular when we approach the singularity.

gr-qc↗

arXiv2014

Towards a Cosmology with Minimal Length and Maximal Energy

The Friedmann-Robertson-Walker (FRW) universe and Bianchi I,II universes are investigated in the framework of the generalized uncertainty principle (GUP) with a linear and a quadratic term in Planck length and momentum, which predicts minimum measurable length as well as maximum measurable momentum. We get a dynamic cosmological bounce for the FRW universe. With Bianchi universe, we found that the universe may be still isotropic by implementing GUP. Moreover, the wall velocity appears to be stationary with respect to the universe velocity which means that when the momentum of the Universe evolves into a maximum measurable energy, the bounce is enhanced against the wall which means no maximum limit angle is manifested anymore.

gr-qc↗

arXiv2013

Exploring viscous damping in undergraduate Physics laboratory using electromagnetically coupled oscillators

We design a low-cost, electromagnetically coupled, simple harmonic oscillator and demonstrate free, damped and forced oscillations in an under-graduate (UG) Physics laboratory. It consists of a spring-magnet system that can oscillate inside a cylinder around which copper coils are wound. Such demonstrations can compliment the traditional way in which a Waves & Oscillations course is taught and offers a richer pedagogical experience for students. We also show that with minimal modifications, it can be used to probe the magnitude of viscous damping forces in liquids by analyzing the oscillations of an immersed magnet. Finally, we propose some student activities to explore non-linear damping effects and their characterization using this apparatus.

physics.ed-ph↗

arXiv2013

Nonsingular Rainbow Universes

In this work, we study FRW cosmologies in the context of gravity rainbow. We discuss the general conditions for having a nonsingular FRW cosmology in gravity rainbow. We propose that gravity rainbow functions can be fixed using two known modified dispersion relation (MDR), which have been proposed in literature. The first MDR was introduced by Amelino-Camelia, et el. in [9] and the second was introduced by Magueijo and Smolin in [24]. Studying these FRW-like cosmologies, after fixing the gravity rainbow functions, leads to nonsingular solutions which can be expressed in exact forms.

gr-qc↗

arXiv2013

The Effects of Minimal Length in Entropic Force Approach

With Verlinde's recent proposal which says that gravity can be identified with an entropic force and considering the effects of generalized uncertainty principle in the black hole entropy-area relation we derive the modified equations for Newton's law of gravitation, modified Newtonian dynamics and Einstein's general relativity. The corrections to the Newtonian potential is compared with the corrections that come from Randall-Sundrum II model and an effective field theoretical model of quantum general relativity. The effect of the generalized uncertainty principle introduces a $\sqrt{\text{Area}}$ type correction term in the entropy area relation whose consequences in different scenarios are discussed.

gr-qc↗

arXiv2013

Black Hole Entropy with minimal length in Tunneling formalism

Here we study the effects of the Generalized Uncertainty Principle in the tunneling formalism for Hawking radiation to evaluate the quantum-corrected Hawking temperature and entropy for a Schwarzschild black hole. We compare our results with the existing results given by other candidate theories of quantum gravity. In the entropy-area relation we found some new correction terms and in the leading order we found a term which varies as $\sim \sqrt{Area}$. We also get the well known logarithmic correction in the sub-leading order. We discuss the significance of this new quantum corrected leading order term.

gr-qc↗