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Kolahal Bhattacharya

Publications and source records attributed to Kolahal Bhattacharya.

17 recordsLinked to original sources
arXiv2025

An exact approach to frustrated total internal reflection and Goos-Hänchen shift for s-polarised light

An exact analogy between wave mechanics in quantum theory and the scalar wave treatment of optics emerges from the marriage of Newtonian formulation of geometrical optics [1] and the ``formal quantum theory of light rays'' [2]. Here the incidence of a ray of light on the interface between two media is treated as the incidence of a wavefunction on a potential barrier. This leads to the coefficient of reflection identical to Fresnel's formula for s-polarised light [3], although there is no concept of the polarisation of light in this model. In the present work, we apply this model to the total internal reflection of light and evanescent waves. We also deduce a one-to-one correspondence between the transmission coefficient in wave mechanics and frustrated total internal reflection for all angles of incidence. Further, we demonstrate that this model can also be used to derive the Goos-Hänchen shift for s-polarised light. This work augments the discussion on these topics found in the standard texts in optics [4].

physics.gen-ph↗
arXiv2025

Pedagogical study of the image of a magnetic dipole in front of a superconducting sphere

The method of images to solve certain electrostatic boundary-value problems is taught worldwide in undergraduate-level physics courses. Though it is also possible to employ this technique for solving magnetostatic boundary value problems, examples of this usage are rarely found in textbooks or physics pedagogy literature. In particular, the problem of finding the field due to a magnetic dipole kept in front of a superconducting sphere is an interesting one, because (i) it helps the students to compare with the grounded conducting sphere image problem in electrostatics, and (ii) offers a greater degree of difficulty since the source is a dipole (vector), rather than an electric charge (scalar). The present work demonstrates an intuitive way of solving the problem. The case in which the source dipole is oriented radially with respect to the sphere is solved with a single dipole image. In the case of the transverse orientation of the source dipole, we model the dipole as a current loop. Then, we find the image of the radial and transverse current elements that satisfy the boundary conditions. Then, we show that this method can be used to deduce the form of the image dipoles when the dipole is oriented in the transverse direction. This method is very much intuitive and accessible for undergraduate-level students.

physics.class-ph↗
arXiv2025

Semi-classical understanding of flux quantization in superconductors

Like electric charge, magnetic flux is also quantised. Theoretically, one can show that the flux quantum must be h/e, as observed in the quantum Hall effect. However, in the superconducting systems, the flux quantum is experimentally observed as h/2e. There is no fundamental explanation for the empirical result. In this article, we argue that this phenomenon is fundamentally linked to the nonlocality problem of the Aharonov-Bohm effect and present a new semi-classical explanation for the magnetic flux quantum in superconductivity. This work will also show why the flux quantum should be h/e in the case of the quantum Hall effect.

physics.gen-ph↗
arXiv2023

Semi-classical description of electrostatics and quantization of electric charge

In this work, we present an explanation of the electric charge quantization based on a semi-classical model of electrostatic fields. We claim that in electrostatics, an electric charge must be equal to a rational multiple of the elementary charge of an electron. However, the charge is quantized if the system has certain boundary conditions that force the wavefunction representing an electric field to vanish at specific surfaces. Next, we develop the corresponding model for the electric displacement vector. It is demonstrated that a number of classical results, e.g. bending of field lines at the interface of two dielectric media, method of images, etc. are all consistent with the predictions of this model. We also present the possible form of Gauss's law or (Poisson's equation), to find the wavefunctions of the field from a source charge distribution, in this model.

physics.gen-ph↗
arXiv2022

A complement to the scalar wave theory of light

In this paper, we discuss how the concepts of Hamiltonian optics are internally connected to the scalar wave theory of light rays. It is shown that the solutions of the reduced wave equation are similar to Huygen's wavelets, and they can be used to understand Snell's law of refraction. This model can also be used to derive the coefficient of reflection consistent with Fresnel's equation for $s$-polarized light.

physics.gen-ph↗
arXiv2021

Unexplored aspects of a variational principle in electrostatics

The electrostatic field magnitude can play a role in a variational principle similar to the role of the index of refraction in geometrical optics, allowing the determination of the electric field lines. This was identified in the context of the grounded conducting sphere image problem. Assuming the knowledge of the magnitude of the electric field, in this paper we validate this principle for the general case and explore some of its consequences.

physics.class-ph↗
arXiv2021

Demystifying the nonlocality problem in Aharonov-Bohm effect

In this paper, we present a novel semi-classical theory of the electrostatic and magnetostatic fields and explain the nonlocality problem in the context of the Aharonov-Bohm effect [1]. Specifically, we show that the electrostatic and the magnetostatic fields possess a quantum nature that manifests if certain conditions are met. In particular, the wave amplitudes of the fields are seen to exist even in the regions where the classical fields vanish and they operate on the electron wave functions locally as unitary phases. This formulation also sheds light on the quantisation of electric charges and magnetic flux.

physics.gen-ph↗
arXiv2020

Scaling the training of particle classification on simulated MicroBooNE events to multiple GPUs

Measurements in Liquid Argon Time Projection Chamber (LArTPC) neutrino detectors, such as the MicroBooNE detector at Fermilab, feature large, high fidelity event images. Deep learning techniques have been extremely successful in classification tasks of photographs, but their application to LArTPC event images is challenging, due to the large size of the events. Events in these detectors are typically two orders of magnitude larger than images found in classical challenges, like recognition of handwritten digits contained in the MNIST database or object recognition in the ImageNet database. Ideally, training would occur on many instances of the entire event data, instead of many instances of cropped regions of interest from the event data. However, such efforts lead to extremely long training cycles, which slow down the exploration of new network architectures and hyperparameter scans to improve the classification performance. We present studies of scaling a LArTPC classification problem on multiple architectures, spanning multiple nodes. The studies are carried out on simulated events in the MicroBooNE detector. We emphasize that it is beyond the scope of this study to optimize networks or extract the physics from any results here. Institutional computing at Pacific Northwest National Laboratory and the SummitDev machine at Oak Ridge National Laboratory's Leadership Computing Facility have been used. To our knowledge, this is the first use of state-of-the-art Convolutional Neural Networks for particle physics and their attendant compute techniques onto the DOE Leadership Class Facilities. We expect benefits to accrue particularly to the Deep Underground Neutrino Experiment (DUNE) LArTPC program, the flagship US High Energy Physics (HEP) program for the coming decades.

physics.comp-ph↗
arXiv2019

Supervised learning of photoelectron counting in scintillator-based dark matter experiments

Many scintillator based detectors employ a set of photomultiplier tubes (PMT) to observe the scintillation light from potential signal and background events. It is important to be able to count the number of photoelectrons (PE) in the pulses observed in the PMTs, because the position and energy reconstruction of the events is directly related to how well the spatial distribution of the PEs in the PMTs as well as their total number might be measured. This task is challenging for fast scintillators, since the PEs often overlap each other in time. Standard Bayesian statistics methods are often used and this has been the method employed in analyzing the data from liquid argon experiments such as MiniCLEAN and DEAP. In this work, we show that for the MiniCLEAN detector it is possible to use a multi-layer perceptron to learn the number of PEs using only raw pulse features with better accuracy and precision than existing methods. This can even help to perform position reconstruction with better accuracy and precision, at least in some generic cases.

physics.ins-det↗
arXiv2019

Triplet Lifetime in Gaseous Argon

MiniCLEAN is a single-phase liquid argon dark matter experiment. During the initial cooling phase, impurities within the cold gas ($<$140 K) were monitored by measuring the scintillation light triplet lifetime, and ultimately a triplet lifetime of 3.480 $\pm$ 0.001 (stat.) $\pm$ 0.064 (sys.) $μ$s was obtained, indicating ultra-pure argon. This is the longest argon triplet time constant ever reported. The effect of quenching of separate components of the scintillation light is also investigated.

physics.ins-det↗
arXiv2017

Physics Potential of the ICAL detector at the India-based Neutrino Observatory (INO)

The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO) is designed to study the atmospheric neutrinos and antineutrinos separately over a wide range of energies and path lengths. The primary focus of this experiment is to explore the Earth matter effects by observing the energy and zenith angle dependence of the atmospheric neutrinos in the multi-GeV range. This study will be crucial to address some of the outstanding issues in neutrino oscillation physics, including the fundamental issue of neutrino mass hierarchy. In this document, we present the physics potential of the detector as obtained from realistic detector simulations. We describe the simulation framework, the neutrino interactions in the detector, and the expected response of the detector to particles traversing it. The ICAL detector can determine the energy and direction of the muons to a high precision, and in addition, its sensitivity to multi-GeV hadrons increases its physics reach substantially. Its charge identification capability, and hence its ability to distinguish neutrinos from antineutrinos, makes it an efficient detector for determining the neutrino mass hierarchy. In this report, we outline the analyses carried out for the determination of neutrino mass hierarchy and precision measurements of atmospheric neutrino mixing parameters at ICAL, and give the expected physics reach of the detector with 10 years of runtime. We also explore the potential of ICAL for probing new physics scenarios like CPT violation and the presence of magnetic monopoles.

physics.ins-det↗
arXiv2016

On the Dependence of Charge Density on Surface Curvature of an Isolated Conductor

A study of the relation between the electrostatic charge density at a point on a conducting surface and the curvature of the surface (at that point) is presented. Two major scientific literature on this topic are reviewed and the apparent discrepancy between them is resolved. Hence, a step is taken towards obtaining a general analytic formula for relating the charge density with surface curvature of conductors. The merit of this formula and its limitations are discussed.

physics.class-ph↗
arXiv2015

Error Propagation of the Track Model and Track Fitting Strategy for the Iron CALorimeter Detector in India-based Neutrino Observatory

A Kalman filter package has been developed for reconstructing muon ($μ^\pm$) tracks (coming from the neutrino interactions) in ICAL detector. Here, we describe the algorithm of muon track fitting, with emphasis on the error propagation of the elements of Kalman state vector along the muon trajectory through dense materials and inhomogeneous magnetic field. The higher order correction terms are included for reconstructing muon tracks at large zenith angle $θ$ (measured from the perpendicular to the detector planes). The performances of this algorithm and its limitations are discussed.

physics.ins-det↗
arXiv2014

A Novel Variational Principle in Electrostatics and its Consequences

We propose a novel variational principle in electrostatics and show that one can derive mirror equation in the context of image problem starting from this principle. The corresponding Euler-Lagrange equation is seen to lead to Green's differential equation (also known as Thomson's equation).

physics.class-ph↗
arXiv2011

Analogy of the grounded conducting sphere image problem with mirror optics

We show that in the grounded conducting sphere image problem, all the necessary information about the image charge can be found from a mirror equation and a magnification formula. Then, we propose a method to solve the image problem for an extended charge distribution near a grounded conducting sphere.

physics.class-ph↗