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V. Srinivasan

Publications and source records attributed to V. Srinivasan.

At least 19 recordsLinked to original sources
arXiv2025

LARK -- Linearizability Algorithms for Replicated Keys in Aerospike

We present LARK (Linearizability Algorithms for Replicated Keys), a synchronous replication protocol that achieves linearizability while minimizing latency and infrastructure cost, at significantly higher availability than traditional quorum-log consensus. LARK introduces Partition Availability Conditions (PAC) that reason over the entire database cluster rather than fixed replica sets, improving partition availability under independent failures by roughly 3x when tolerating one failure and 10x when tolerating two. Unlike Raft, Paxos, and Viewstamped Replication, LARK eliminates ordered logs, enabling immediate partition readiness after leader changes -- with at most a per-key duplicate-resolution round trip when the new leader lacks the latest copy. Under equal storage budgets -- where both systems maintain only f+1 data copies to tolerate f failures -- LARK continues committing through data-node failures while log-based protocols must pause commits for replica rebuilding. These properties also enable zero-downtime rolling restarts even when maintaining only two copies. We provide formal safety arguments and a TLA+ specification, and we demonstrate through analysis and experiments that LARK achieves significant availability gains.

cs.DC↗
arXiv2024

Growth of a Bubble Under a Fluctuating Pressure Field

This study seeks to understand the origins of intermittency in quantities of interest in pool boiling, such as bubble departure diameter and departure time. The intermittency of nucleation site activity due to nonuniform and unsteady near-wall temperatures is well-established; however, few mechanistic models have been developed that predict such intermittency. Here we assume a fluctuating pressure field at a nucleation site due to adjacent bubble activity, which acts in combination with convective effects to alter bubble growth depending on the phase of the pressure oscillation with respect to the instant of bubble nucleation. The results suggest that even when a single departure frequency is assumed for nearby bubbles, its effect on the nucleation site being considered is to cause aperiodicity and intermittency in bubble departure quantities. The effects of pressure field phase angle, degree of superheat, and choice of force balance model on the bubble departure quantities are examined. The phase angle of the pressure fluctuation at the instant of bubble nucleation is shown to play a major role in determining bubble departure diameter and growth time. Departure diameter is observed to have a broad distribution over long times of observation, belying the assumption of a unique value. Period doubling of the ebullition cycle is observed for some conditions, a phenomenon documented by other investigators. The effects of dynamic contact angle.

physics.flu-dyn↗
arXiv2020

A measure for adiabatic contributions to quantum transitions

We construct a measure for the adiabatic contribution to quantum transitions in an arbitrary basis, tackling the generic complex case where dynamics is only partially adiabatic, simultaneously populates several eigenstates and transitions between non-eigenstates are of key interest. Our measure is designed to distinguish transitions between basis states that occur due to the adiabatic change of the underlying populated eigenstates from transitions that occur due to beating between several such eigenstates. We demonstrate that the measure can be applied to material or molecular simulations using time-dependent density functional theory, allowing to quantify the relative importance of adiabaticity and thus nuclear motion, for example, in charge or energy transfer.

quant-ph↗
arXiv2019

Some results on topological currents in field theory

A few exact results concerning topological currents in field theories are obtained. It is generally shown that, a topological charge can not generate any kind of symmetry transformation on the fields. It is also proven that, the existence of a charge that does not generate any kind of symmetry transformation on the fields, has to be of topological origin. As a consequence, it is found that in a given theory, superconductivity via Anderson-Higgs route can only occur if the gauge coupling with other fields is minimal. Several physical implications of these results are studied.

hep-th↗
arXiv2018

Learning The Invisible: A Hybrid Deep Learning-Shearlet Framework for Limited Angle Computed Tomography

The high complexity of various inverse problems poses a significant challenge to model-based reconstruction schemes, which in such situations often reach their limits. At the same time, we witness an exceptional success of data-based methodologies such as deep learning. However, in the context of inverse problems, deep neural networks mostly act as black box routines, used for instance for a somewhat unspecified removal of artifacts in classical image reconstructions. In this paper, we will focus on the severely ill-posed inverse problem of limited angle computed tomography, in which entire boundary sections are not captured in the measurements. We will develop a hybrid reconstruction framework that fuses model-based sparse regularization with data-driven deep learning. Our method is reliable in the sense that we only learn the part that can provably not be handled by model-based methods, while applying the theoretically controllable sparse regularization technique to the remaining parts. Such a decomposition into visible and invisible segments is achieved by means of the shearlet transform that allows to resolve wavefront sets in the phase space. Furthermore, this split enables us to assign the clear task of inferring unknown shearlet coefficients to the neural network and thereby offering an interpretation of its performance in the context of limited angle computed tomography. Our numerical experiments show that our algorithm significantly surpasses both pure model- and more data-based reconstruction methods.

cs.CV↗
arXiv2018

Separability Criterion for Multi-Mode Gaussian States

In this paper, we give Separability criterion for the multi-mode Gaussian states using the Marchenko-Pastur theorem. We show that the Marchenko-Pastur theorem from random matrix theory as necessary and sufficient condition for separability of multimode Gaussian states.

quant-ph↗
arXiv2017

Light-matter interaction and Bose-Einstein condensation of light

The atom - electromagnetic field interaction is studied in the Dicke model, wherein a single field mode is interacting with a collection of two level atoms at thermal equilibrium. It is found that in the superradiant phase of the system, wherein the Bose-Einstein condensation of photons takes place, the notion of photon as an elementary electromagnetic excitation ceases to exist. The phase and intensity excitations of the condensate are found to be the true excitations of electromagnetic field. It is found that in this phase, the atom interacts with these excitations in a distinct coherent transition process, apart from the known stimulated emission/absorption and spontaneous emission processes. In the coherent transition it is found that while the atomic state changes in course of the transition process, the state of electromagnetic field remains unaffected. It is found that the transition probability of such coherent transition process is macroscopically large compared to other stimulated emission/absorption and spontaneous emission processes.

physics.optics↗
arXiv2015

A gauge theory of massive spin one particles

An Abelian gauge theory describing dynamics of massive spin one bosons is constructed. This is achieved by appending to the Maxwell action, a gauge invariant mass term. The theory is quantised in temporal as well as Lorentz gauge, and the corresponding Hilbert spaces are constructed. In both the gauges, it is found that, the theory respects Lorentz invariance, locality, causality and unitarity.

hep-th↗
arXiv2014

Entanglement in two site Bose-Hubbard model

In this paper, we study the decoherence and entanglement properties for the two site Bose-Hubbard model in the presence of a non-linear damping. We apply the techniques of thermo field dynamics and then use Hartree-Fock approximation to solve the corresponding master equation. The expectation values of the approximated field operators appearing in the solution of master equation, are computed self-consistently. We solve this master equation for a small time $t$ so that we get the analytical solution, thereby we compute the decoherence and entanglement properties of the solution of the two-mode bosonic system.

quant-ph↗
arXiv2012

The Kerr medium as an {\sf SU(2)} system

The Kerr medium in the presence of damping and associated with SU(1,1) symmetry, is solved using the techniques of Thermo field Dynamics (TFD).These TFD techniques, well studied earlier (Chaturvedi and Srinivasan, 1991), help us to exactly solve the Kerr medium as a spin damped system associated with SU(2) symmetry. Using TFD, the association with SU(2) is exploited to express the dynamics of the system as a Schrodinger-like equation, whose solution is obtained using the appropriate disentanglement theorem. These considerations are extended to a system with multi-mode coupled nonlinear oscillators."

quant-ph↗
arXiv2012

Exceptional Polynomials and SUSY Quantum Mechanics

We show that the existence of exceptional polynomials leads to the presence of non-trivial supersymmetry. The existence of these polynomials reveals several distinct isospectral potentials for the Schrödinger equation. All Schrödinger equations having Laguerre and Jacobi polynomials as their solutions, have non-trivial supersymmetric partners with corresponding exceptional polynomials as solutions.

math-ph↗
arXiv2009

Strain engineering and one-dimensional organization of metal-insulator domains in single-crystal VO2 beams

Spatial phase inhomogeneity at the nano- to microscale is widely observed in strongly-correlated electron materials. The underlying mechanism and possibility of artificially controlling the phase inhomogeneity are still open questions of critical importance for both the phase transition physics and device applications. Lattice strain has been shown to cause the coexistence of metallic and insulating phases in the Mott insulator VO2. By continuously tuning strain over a wide range in single-crystal VO2 micro- and nanobeams, here we demonstrate the nucleation and manipulation of one-dimensionally ordered metal-insulator domain arrays along the beams. Mott transition is achieved in these beams at room temperature by active control of strain. The ability to engineer phase inhomogeneity with strain lends insight into correlated electron materials in general, and opens opportunities for designing and controlling the phase inhomogeneity of correlated electron materials for micro- and nanoscale device applications.

cond-mat.str-el↗
arXiv2008

Two elementary proofs of the Wigner theorem on symmetry in quantum mechanics

In quantum theory, symmetry has to be defined necessarily in terms of the family of unit rays, the state space. The theorem of Wigner asserts that a symmetry so defined at the level of rays can always be lifted into a linear unitary or an antilinear antiunitary operator acting on the underlying Hilbert space. We present a proof of this theorem which is both elementary and economical. Central to our proof is the recognition that a given Wigner symmetry can, by post-multiplication by a unitary symmetry, be taken into either the identity or complex conjugation. Our analysis involves a judicious interplay between the effect a given Wigner symmetry has on certain two-dimensional subspaces and the effect it has on the entire Hilbert space.

quant-ph↗
arXiv2006

Hamilton's Turns for the Lorentz Group

Hamilton in the course of his studies on quaternions came up with an elegant geometric picture for the group SU(2). In this picture the group elements are represented by ``turns'', which are equivalence classes of directed great circle arcs on the unit sphere $S^2$, in such a manner that the rule for composition of group elements takes the form of the familiar parallelogram law for the Euclidean translation group. It is only recently that this construction has been generalized to the simplest noncompact group $SU(1,1) = Sp(2, R) = SL(2,R)$, the double cover of SO(2,1). The present work develops a theory of turns for $SL(2,C)$, the double and universal cover of SO(3,1) and $SO(3,C)$, rendering a geometric representation in the spirit of Hamilton available for all low dimensional semisimple Lie groups of interest in physics. The geometric construction is illustrated through application to polar decomposition, and to the composition of Lorentz boosts and the resulting Wigner or Thomas rotation.

quant-ph↗
arXiv2004

A Possible universal definition for the nanophase

A possible universal definition for a nanostructured material based purely on experimental data available in literature for a wide variety of physical phenomena is proposed. It is suggested that for values of the ratio of sample volume, V to that of the unit cell volume, Vc, 10^5- 10^6 the samples behave as nanostructures. This is mirrored in the ratio of the number of particles in sample, N to that in the unit cell, Nc. It is further proposed that the transition to the nanophase from bulk is a phase transition in all cases investigated. The nanophase should therefore be treated as a distinct phase of matter, entirely in the quantum mechanical domain, and treated appropriately.

cond-mat.mtrl-sci↗
arXiv2000

Coherent States of Non-Linear Algebras:Application to Quantum Optics

We present a general unified approach for finding the coherent states of polynomially deformed algebras such as the quadratic and Higgs algebras, which are relevant for various multiphoton processes in quantum optics. We give a general procedure to map these deformed algebras to appropriate Lie algebras. This is used, for the non compact cases, to obtain the annihilation operator coherent states, by finding the canonical conjugates of these operators. Generalized coherent states, in the Perelomov sense also follow from this construction. This allows us to explicitly construct coherent states associated with various quantum optical systems.

quant-ph↗
arXiv1999

Coherent States of Non-Linear Lie algebras: Application in Quantum Optics

We present a general unified approach for finding the coherent states of polynomially deformed algebras such as the quadratic and Higgs algebras, which are relevant for various multiphoton processes in quantum optics. We give a general procedure to map these deformed algebras to appropriate Lie algebras. This is used, for the non compact cases, to obtain the annihilation operator coherent states, by finding the canonical conjugates of these operators. Generalized coherent states, in the Perelomov sense also follow from this construction. This allows us to explicitly construct coherent states associated with various quantum optical systems.

quant-ph↗