arXiv subjects

R. Ramanathan

Publications and source records attributed to R. Ramanathan.

13 recordsLinked to original sources

arXiv2016

Completely Device Independent Quantum Key Distribution

Quantum key distribution (QKD) is a provably secure way for two distant parties to establish a common secret key, which then can be used in a classical cryptographic scheme. Using quantum entanglement, one can reduce the necessary assumptions that the parties have to make about their devices, giving rise to device-independent QKD (DIQKD). However, in all existing protocols to date the parties need to have an initial (at least partially) random seed as a resource. In this work, we show that this requirement can be dropped. Using recent advances in the fields of randomness amplification and randomness expansion, we demonstrate that it is sufficient for the message the parties want to communicate to be (partially) unknown to the adversaries -- an assumption without which any type of cryptography would be pointless to begin with. One party can use her secret message to locally generate a secret sequence of bits, which can then be openly used by herself and the other party in a DIQKD protocol. Hence, our work reduces the requirements needed to perform secure DIQKD and establish safe communication.

quant-ph↗

arXiv2015

Speed of sound in quark gluon plasma with one loop correction in mean field potential

We study thermodynamic properties and speed of sound in a free en- ergy evolution of quark-gluon plasma (QGP) with one loop correction factor in the mean-field potential. The values of the thermodynamic prop- erties like pressure, entropy and specific heat are calculated for a range of temperatures. The results agree with the recent lattice results. The speed of sound is found to be C2 s = 0.3 independent of parameters used in the loop correction which matches almost with lattice calculations.

hep-ph↗

arXiv2014

Approximate probabilistic verification of hybrid systems

Hybrid systems whose mode dynamics are governed by non-linear ordinary differential equations (ODEs) are often a natural model for biological processes. However such models are difficult to analyze. To address this, we develop a probabilistic analysis method by approximating the mode transitions as stochastic events. We assume that the probability of making a mode transition is proportional to the measure of the set of pairs of time points and value states at which the mode transition is enabled. To ensure a sound mathematical basis, we impose a natural continuity property on the non-linear ODEs. We also assume that the states of the system are observed at discrete time points but that the mode transitions may take place at any time between two successive discrete time points. This leads to a discrete time Markov chain as a probabilistic approximation of the hybrid system. We then show that for BLTL (bounded linear time temporal logic) specifications the hybrid system meets a specification iff its Markov chain approximation meets the same specification with probability $1$. Based on this, we formulate a sequential hypothesis testing procedure for verifying -approximately- that the Markov chain meets a BLTL specification with high probability. Our case studies on cardiac cell dynamics and the circadian rhythm indicate that our scheme can be applied in a number of realistic settings.

eess.SY↗

arXiv2014

Are atomic clocks slowing down? Possible connection between the quantum and the cosmos: A feasible experimental test of objective realism

An alternative to the current accepted model of expanding universe is presented. The proposal is anchored in the objective realist, stochastic formulation of quantum mechanics wherein the Planck constant plays the role of a diffusion constant which need not be an universal constant for all epochs. This underlying noise is charecterised by a very high initial value of the Planck constant which gradually decreased over the epochs gone by, finally reaching its present value .It is this decrease in the strength of the Planck constant that causes a spectral red shift with the passage of time .The compatibility of this proposal with some cosmological data is shown.Feasible spectroscopic measurement of a specific spectral line frequency done over a period of a few years can decisively either validate or invalidate the proposal in a terrestrially bound experiment. This proposal predicts a slowing down of atomic clocks by nearly 2. 10^-18 s with respect to every preceding second. A positive experimental outcome will validate the objective realist basis of quantum physics as advocated by Einstein and many others.

physics.gen-ph↗

arXiv2011

Correlation complementarity yields Bell monogamy relations

We present a method to derive Bell monogamy relations by connecting the complementarity principle with quantum non-locality. The resulting monogamy relations are stronger than those obtained from the no-signaling principle alone. In many cases, they yield tight quantum bounds on violation of single and multiple qubit correlation Bell inequalities. In contrast with the two-qubit case, a rich structure of possible violation patterns is shown to exist in the multipartite scenario.

quant-ph↗

arXiv2011

A model density of states for Quarks and Gluons in QGP

We propose an algebraic form for the density of states of quarks and gluons in a Quark-Gluon Plasma (QGP) fireball in quasi-equilibrium with a hadronic medium as $ρ(k)= \frac α{k} + βk + δk^{2}$, and determine the parameters $α$, $β$ and $δ$ using Lattice Gauge results on the velocity of sound in QGP. The behaviour of the resulting $ρ(k)$ can be easily compared with the thermodynamic data on QGP that is expected from LHC and other RHIC experiments. Our numerical result shows a linear rise of the value of $ρ(k)$ for $k\sim T \approx 160 to 180 MeV$, which is significant, and throws light on the evolution of the QGP phase.

hep-ph↗

arXiv2009

The phase structure of QGP-Hadron in a statistical model using Cornell, Richardson and Peshier potentials

We study the phase structure of the QGP-Hadron system under quasi-static equilibrium using the Ramanathan et al. statistical model for the QGP fireball formation in a hadronic medium. While in the earlier published studies we had used the Peshier effective potential which is appropriate for the deconfined QGP phase but could be extrapolated to the transition region from the higher momentum regime, in this paper we study the same system using the Cornell and Richardson potentials which are more relevant for the low momentum confinement regime, but could again be extrapolated to the transition region from below. Surprisingly, the overall picture in both the cases are quite similar with minor divergences,(though,the results with the Richardson potential shows a sizable deviation from the other two potentials), thus indicating the robustness of the model and its self-consistency. The result of our numerical results pertaining to the variation of the velocity of sound in the QGP-Hadron medium with temperature in the various scenarios considered by us, is that, the phase transition seems to be a gentle roll-over of phases rather than a sharp transition of either the first or second order, a result in conformity with recent lattice calculations, but with much less effort.

hep-ph↗

arXiv2008

Effect of finite chemical potential on QGP-Hadron phase transition in a statistical model of fireball formation

We study the effect of finite chemical potential for the QGP constituents in the Ramanathan et al. statistical model (Phys.Rev.C70, 027903,2004). While the earlier computations using this model with vanishing chemical potentials indicated a weakly first order phase transition for the system in the vicinity of 170 MeV (Pramana, 68, 757, 2007), the introduction of finite values for the chemical potentials of the constituents makes the transition a smooth roll over of the phases, while allowing fireball formation with radius of a few "fermi" to take place. This seems to be in conformity with the latest consensus on the nature of the QGP-Hadron phase transition. Keywords: Quark Gluon Plasma, Quark Hadron Phase Transition

hep-ph↗

arXiv2005

Thermal and interfacial properties of a Quark Gluon Plasma droplet in a hadronic medium via a statistical model

Thermal and interfacial properties of a QGP droplet in a hadronic medium are computed using a statistical model of the system. The results indicate a weakly first order transition at a transition temperature \sim (160 \pm 5) MeV. The interfacial surface tension is proportional to the cube of the transition temperaure irrespective of the magnitude of the transition temperature. The velocity of sound in the QGP droplet is predicted to be in the range (0.27 \pm 0.02) times the velocity of light in vacuum, and this value is seen to be independent of the value of the transition temperature as well as the model parameters. These predictions are in remarkable agreement with Lattice Simulation results and extant MIT Bag model predictions.

hep-ph↗

arXiv2005

A Comparative Study of Two Models of QGP-Fireball Formation

A Comparative study of the strengths and weakness of the models of fireball formation namely the statistical model of Ramanathan et.al (Physical Review C 70, 027903, 2004) and the approximation schemes of Kapusta et. al (Physical Review D 46, 1379, 1992) and its subsequent improved variants is made. The way to complement the various approximation schemes, in order to enhance their utility in the phenomenological analysis of QGP data that are expected from ongoing URHIC experiments, is suggested. The calculations demonstrate a striking QCD behaviour of the surface tension of the QGP droplet resulting in its increase with temperature, which is due to the confining nature of QCD forces at the surface and the interface surface tension varies as the cube of the transition temperature which is in conformity with the results of Lattice QCD simulations.

hep-ph↗

arXiv2004

A Simple Statistical Model for Analysis of QGP-droplet (Fireball) Formation

We construct the density of states for quarks and gluons using the `Thomas - Fermi model' for atoms and the `Bethe model' for nucleons as templates. With parameters to take care of the plasma (hydrodynamical) features of the QGP with a thermal potential for the interaction, we find a window in the parametric space of the model where observable QGP droplets of $ \sim $ 5 fm radius can occur with transition temperature in the range 140 MeV to 250 MeV. By matching with the expectations of Lattice Gauge estimates of the QGP-hadron transitions, we can further narrow the window, thereby restricting the allowed values of the flow-parameters of the model.

hep-ph↗

arXiv2004

A Simple Statistical Model for QGP Phenomenology

We propose a simple statistical model for the density of states for quarks and gluons in a QGP droplet, making the Thomas-Fermi model of the atom and the Bethe-model for the nucleons as templates for constructing the density of states for the quarks and gluons with due modifications for the `hot' relativistic QGP state as against the `cold' non-relativistic atom and nucleons, which were the subject of the earlier `forebears' of the present proposal.We introduce `flow-parameters' $γ_{q,g}$ for the quarks and the gluons to take care of the hydrodynamical (plasma) flows in the QGP system as was done earlier by Peshier in his thermal potential for the QGP. By varying $γ_{g}$ about the `Peshier-Value' of $γ_{q} = 1/6$, we find that the model allows a window in the parametric space in the range $8γ_{q} \leq γ_{g} \leq 12γ_{q}$, with $γ_{q} =1/6$ (Peshier-Value), when stable QGP droplets of radii $\sim$ $6 fm$ appear at transition temperatures $100 MeV \leq T \leq 250 MeV$. The smooth cut at the phase boundary of the Free energy vs. droplet radius suggests a First - Order phase transition .On the whole the model offers a robust tool for studying QGP phenomenology as and when data from various ongoing experiments are available .

hep-ph↗

arXiv1998

On Simulating Liouvillian Flow From Quantum Mechanics Via Wigner Functions

The interconnection between quantum mechanics and probabilistic classical mechanics for a free relativistic particle is derived in terms of Wigner functions (WF) for both Dirac and Klein-Gordon (K-G) equations. Construction of WF is achieved by first defining a bilocal 4-current and then taking its Fourier transform w.r.t. the relative 4-coordinate. The K-G and Proca cases also lend themselves to a closely parallel treatment provided the Kemmer- Duffin beta-matrix formalism is employed for the former. Calculation of WF is carried out in a Lorentz-covariant fashion by standard `trace' techniques. The results are compared with a recent derivation due to Bosanac.

hep-th↗