arXiv subjects

B. Chakrabarti

Publications and source records attributed to B. Chakrabarti.

32 records · Page 2Linked to original sources

arXiv2015

Many-body entropies, correlations, and emergence of statistical relaxation in interaction quench dynamics of ultracold bosons

We study the quantum many-body dynamics and the entropy production triggered by an interaction quench in a system of $N=10$ interacting identical bosons in an external one-dimensional harmonic trap. The multiconfigurational time-dependent Hartree method for bosons (MCTDHB) is used for solving the time-dependent Schrödinger equation at a high level of accuracy. We consider many-body entropy measures such as the Shannon information entropy, number of principal components, and occupation entropy that are computed from the time-dependent many-body basis set used in MCTDHB. These measures quantify relevant physical features such as irregular or chaotic dynamics, statistical relaxation and thermalization. We monitor the entropy measures as a function of time and assess how they depend on the interaction strength. For larger interaction strength, the many-body information entropy approaches the value predicted for the Gaussian orthogonal ensemble of random matrices and implies statistical relaxation. The basis states of MCTDHB are explicitly time-dependent and optimized by the variational principle in a way that minimizes the number of significantly contributing ones. It is therefore a non-trivial fact that statistical relaxation prevails in MCTDHB computations. Moreover, we demonstrate a fundamental connection between the production of entropy, the build-up of correlations and loss of coherence in the system. Since the coherence and correlations are experimentally accessible, their present connection to many-body entropies can be scrutinized to detect statistical relaxation. Our results are the first ones obtained for thermalization of finite quantum systems using an optimized time-dependent and genuinely many-body basis set.

cond-mat.quant-gas↗

arXiv2014

$α-γ$ transition in cerium: magnetic form factor and dynamic magnetic susceptibility in dynamical mean-field theory

The nature of the elemental cerium phases, undergoing an isostructural volume collapse transition, cannot be understood using conventional solid state concepts. Using the combination of density functional theory and dynamical mean-field theory, we study the magnetic properties of both the $α$ and the $γ$ phases. We compute the magnetic form factor, and show that it is very close to free ion behavior in both the local moment $γ$ phase as well as the more itinerant $α$ phase, in agreement with neutron scattering experiments. In sharp contrast, the dynamic local magnetic susceptibility of the two phases is strikingly different. In the $γ$ phase, the sharp low energy peak due to local moment formation and consequently low Kondo temperature dominates the spectra. In the $α$ phase two broad peaks can be identified, the first is due to Kondo screening, and the second is due to Hund's coupling. This shows that hybridization plays a central role in the $α-γ$ transition in cerium, and that from the point of view of magnetic properties, the $4f$ electrons are strongly correlated in both phases.

cond-mat.str-el↗

arXiv2013

Composite Fermion Approach to Diquark and Heavy-Light Baryon Masses

A composite Fermion (CF) model of quasi particle has been used to describe a diquark. Considering baryons in quark-diquark configuration,the masses of the heavy light baryons like $Λ_{c}^{+}$, $Σ_{c}^{+}$, $Ξ_{c}^{0}$, $Ω_{c}^{0}$ and $Λ_{b}^{+}$, $Σ_{b}^{+}$, $Ξ_{b}^{0}$, $Ω_{b}^{-}$ have been computed using this CF model of the diquark. The results are found to be in good agreement with the corresponding experimental findings. It has been suggested that the diquark can be well described in the framework of CF model in a gauge invariant way.

hep-ph↗

arXiv2013

Strangeness in proton and properties of nucleons in nuclear matter revisited

The properties of the nucleons in nuclear medium have been investigated in the context of the flux tube model incorporating strangeness $(s\bar{s})$ contribution to proton structure in conformity with the experimental indication. Proton is described as a pentaquark system with strange quark contribution whereas neutron is described in three quark configuration. The Quasi particle model of diquark is used to describe the structures of the nucleons. Modifications of the properties like swelling, mass, incompressibility, ratio of the structure functions ($\frac{F_{2}^{n}(x)}{F_{2}^{p}(x)}$), Gottfried Sum rule for nucleons in nuclear medium have been studied and significant effects have been observed. It has been suggested that the change of the size degree of freedom of the nucleon in the nuclear medium plays an important role in describing the properties in medium. The results are discussed in detail and compared with existing experimental and theoretical predictions. Some interesting observations are made.

hep-ph↗

arXiv2012

Bio-Polymer Hairpin Loops Sustained by Polarons

We show that polarons can sustain loop-like configurations in flexible bio-polymers and that the size of the loops depend on both the flexural rigidity of the polymer and the electron-phonon coupling constant. In particular we show that for single stranded DNA (ssDNA) such loops can have as little as 10 base pairs. For polyacetylene the shortest loop must have at least 12 nodes. We also show that these configurations are very stable under thermal fluctuations and can facilitate the formation of hairpin-loops of ssDNA.

physics.bio-ph↗

arXiv2011

Fractal Space Time and Variation of Fine Structure Constant

The effect of fractal space time of the quantum particles on the variation of the fine structure constant $α$ has been studied. The variation of fine structure constant has been investigated around De Broglie length $λ$ and compton length $λ_{c}$ and it has been suggested that the variation may be attributed to the dimensional transition of the particle trajectories between these two quantum domains. Considering the Fractal universe with a small inhomogeneity in the mass distribution in the early universe, the variation of the fine structure constant have been investigated between matter and radiation dominated era. The fine structure constant shows a critical behaviour with critical exponent which is fractional and shows a discontinuity. It has been suggested that the variation of the fine structure constant may be attributed to the intrinsic scale dependance of the fundamental constants of nature.

astro-ph.CO↗

arXiv2011

Spontaneous Polaron Transport in Biopolymers

Polarons, introduced by Davydov to explain energy transport in $α$-helices, correspond to electrons localised on a few lattice sites because of their interaction with phonons. While the static polaron field configurations have been extensively studied, their displacement is more difficult to explain. In this paper we show that, when the next to nearest neighbour interactions are included, for physical values of the parameters, polarons can spontaneously move, at T=0, on bent chains that exhibit a positive gradient in their curvature. At room temperature polarons perform a random walk but a curvature gradient can induce a non-zero average speed similar to the one observed at zero temperature. We also show that at zero temperature a polaron bounces on sharply kinked junctions. We interpret these results in light of the energy transport by transmembrane proteins.

cond-mat.stat-mech↗

arXiv2010

Nucleon in Nuclear Matter

The modification of the properties of nucleon in nuclear medium have been investigated in the context of flux tube model. A nucleon has been described as diquark-quark system connected by flux tube and quasi particle diquark model has been used to describe the diquak constituting the nucleon. The modification of incompressiblity, the roper resonance etc in the nuclear medium have been investigated. The results are compared with recent experimental and theoretical predictions.

hep-ph↗

arXiv2008

Temperature Dependent Structure Function Of Nucleon

A relation between temperature, Fermi momentum and radius of the nucleon has been derived. The percentage increase in radii of the nucleon with temperature and the temperature dependent F$_{2}$ structure function of the nucleon have been investigated. An estimate of the Fermi momentum of the nucleon has been made. The results are found to be in agreement with existing theoretical and experimental suggestions .

hep-ph↗

arXiv2008

On Some properties of Di-hadronic states

The binding energies of di- hadronic states have been calculated assuming a 'molecular' interaction provided by the asymptotic expression of the residual confined gluon exchange potential between the component hadrons in the system. Meson- meson and meson- baryon states have been studied in detail and a mass formula has been used to calculate total mass of the 'molecules'.

hep-ph↗

arXiv2008

A Study on the Structure Functions and the radius of the Nucleons

We have investigated the properties of the structure functions of the nucleons in the context of the statistical model using only the radius parameter of the respective nucleons. The radius of the neutron has been estimated and is found to be 0.8fm. It is interesting to observe that the proton radius 0.865fm which exactly equals to the most accepted charge radius of the proton and which in turn characterizes proton as a meso object, yields reasonable results for the structure function and its properties. GT sum rule has been investigated with some interesting conclusions.

hep-ph↗

arXiv2006

On some properties of Exotic Baryons in Quasi particle diquark model

The properties of the Theta^{+} and Xi^{--}_{3/2} exotic baryons have been investigated in the framework of diquark- diquark-antiquark system. A model for diquark suggested in an analogy with the quasi-particle in a crystal lattice has been used. The mass of the exotics have been computed. The Decay width of the Theta^{+} has been estimated to be ~ 11 MeV using effective diquark theory. The radius of the Xi^{--}_{3/2} has been extracted as 0.94fm using the experimental value of the frac{Γ_{Θ^{+}}}{Γ_{Ξ^{--}_{3/2}}}. The results obtained are found to be in good agreement with the present experimental and theoretical suggestions.

hep-ph↗

arXiv2004

Potential Harmonics Expansion Method for Trapped Interacting Bosons : Inclusion of Two-Body Correlation

We study a system of $A$ identical interacting bosons trapped by an external field by solving ab initio the many-body Schroedinger equation. A complete solution by using, for example, the traditional hyperspherical harmonics (HH) basis develops serious problems due to the large degeneracy of HH basis, symmetrization of the wave function, calculation of the matrix elements, etc. for large $A$. Instead of the HH basis, here we use the "potential harmonics" (PH) basis, which is a subset of HH basis. We assume that the contribution to the orbital and grand orbital [in $3(A-1)$-dimensional space of the reduced motion] quantum numbers comes only from the interacting pair. This implies inclusion of two-body correlations only and disregard of all higher-body correlations. Such an assumption is ideally suited for the Bose-Einstein condensate (BEC), which is extremely dilute. Unlike the $(3A-4)$ hyperspherical variables in HH basis, the PH basis involves only three {\it{active}} variables. It drastically reduces the number of coupled equations and calculation of the potential matrix becomes tremendously simplified, as it involves integrals over only three variables for any $A$. One can easily incorporate realistic atom-atom interactions in a straight forward manner. We study the ground and excited state properties of the condensate for both attractive and repulsive interactions for various particle number.

quant-ph↗

arXiv2003

Nonequilibrium phase transition in surface growth

Conserved growth models that exhibit a nonlinear instability in which the height (depth) of isolated pillars (grooves) grows in time are studied by numerical integration and stochastic simulation. When this instability is controlled by the introduction of an infinite series of higher-order nonlinear terms, these models exhibit, as function of a control parameter, a non-equilibrium phase transition between a kinetically rough phase with self-affine scaling and a phase that exhibits mound formation, slope selection and power-law coarsening.

cond-mat.stat-mech↗