DSpace Collection:
http://hdl.handle.net/2289/144
2017-07-25T23:15:38ZNegative partial density of states in mesoscopic systems
http://hdl.handle.net/2289/6673
Title: Negative partial density of states in mesoscopic systems
Authors: Satpathi, Urbashi; Deo, Singha P.
Abstract: Since the experimental observation of quantum mechanical scattering phase shift in mesoscopic systems, several aspects of it have not yet been understood. The experimental observations have also accentuated many theoretical problems related to Friedel sum rule and negativity of partial density of states. We address these problems using the concepts of Argand diagram and Burgers circuit. We can prove the possibility of negative partial density of states in mesoscopic systems. Such a conclusive and general evidence cannot be given in one, two or three dimensions. We can show a general connection between phase drops and exactness of semi classical Friedel sum rule. We also show Argand diagram for a scattering matrix element can be of few classes based on their topology and all observations can be classified accordingly.
Description: Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)2016-12-01T00:00:00ZExact distributions of cover times for N independent random walkers in one dimension
http://hdl.handle.net/2289/6666
Title: Exact distributions of cover times for N independent random walkers in one dimension
Authors: Majumdar, Satya N.; Sabhapandit, Sanjib; Schehr, Gregory
Abstract: We study the probability density function (PDF) of the cover time tc of a finite interval of size L by N independent one-dimensional Brownian motions, each with diffusion constant D. The cover time tc is the minimum time needed such that each point of the entire interval is visited by at least one of the N walkers. We derive exact results for the full PDF of tc for arbitrary N≥1 for both reflecting and periodic boundary conditions. The PDFs depend explicitly on N and on the boundary conditions. In the limit of large N, we show that tc approaches its average value of ⟨tc⟩≈L2/(16DlnN) with fluctuations vanishing as 1/(lnN)2. We also compute the centered and scaled limiting distributions for large N for both boundary conditions and show that they are given by nontrivial N independent scaling functions.
Description: Open Access2016-12-01T00:00:00ZFluctuation theorem for entropy production of a partial system in the weak-coupling limit
http://hdl.handle.net/2289/6664
Title: Fluctuation theorem for entropy production of a partial system in the weak-coupling limit
Authors: Gupta, Deepak; Sabhapandit, Sanjib
Abstract: Small systems in contact with a heat bath evolve by stochastic dynamics. Here we show that, when one such small system is weakly coupled to another one, it is possible to infer the presence of such weak coupling by observing the violation of the steady-state fluctuation theorem for the partial entropy production of the observed system. We give a general mechanism due to which the violation of the fluctuation theorem can be significant, even for weak coupling. We analytically demonstrate on a realistic model system that this mechanism can be realized by applying an external random force to the system. In other words, we find a new fluctuation theorem for the entropy production of a partial system, in the limit of weak coupling.
Description: Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)2016-09-01T00:00:00ZActive fluidization in dense glassy systems
http://hdl.handle.net/2289/6614
Title: Active fluidization in dense glassy systems
Authors: Mandal, Rituparno; Bhuyan, Pranad Jyoti; Rao, Madan; Dasgupta, Chandan
Abstract: Dense soft glasses show strong collective caging behavior at sufficiently low temperatures. Using molecular dynamics simulations of a model glass former, we show that the incorporation of activity or self-propulsion, f0, can induce cage breaking and fluidization, resulting in the disappearance of the glassy phase beyond a critical f0. The diffusion coefficient crosses over from being strongly to weakly temperature dependent as f0 is increased. In addition, we demonstrate that activity induces a crossover from a fragile to a strong glass and a tendency of active particles to cluster. Our results are of direct relevance to the collective dynamics of dense active colloidal glasses and to recent experiments on tagged particle diffusion in living cells.
Description: Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)2016-08-01T00:00:00Z