2,959 research outputs found
Renormalized Path Integral in Quantum Mechanics
We obtain direct, finite, descriptions of a renormalized quantum mechanical
system with no reference to ultraviolet cutoffs and running coupling constants,
in both the Hamiltonian and path integral pictures. The path integral
description requires a modification to the Wiener measure on continuous paths
that describes an unusual diffusion process wherein colliding particles
occasionally stick together for a random interval of time before going their
separate ways.Comment: 13 pgs, plain TEX fil
Disparity between the Programmatic Views and the User Perceptions of Mobile Apps
User perception in any mobile-app ecosystem, is represented as user ratings of apps. Unfortunately, the user ratings are often biased and do not reflect the actual usability of an app. To address the challenges associated with selection and ranking of apps, we need to use a comprehensive and holistic view about the behavior of an app. In this paper, we present and evaluate Trust based Rating and Ranking (TRR) approach. It relies solely on an apps' internal view that uses programmatic artifacts. We compute a trust tuple (Belief, Disbelief, Uncertainty - B, D, U) for each app based on the internal view and use it to rank the order apps offering similar functionality. Apps used for empirically evaluating the TRR approach are collected from the Google Play Store. Our experiments compare the TRR ranking with the user review-based ranking present in the Google Play Store. Although, there are disparities between the two rankings, a slightly deeper investigation indicates an underlying similarity between the two alternatives
Relative volume of separable bipartite states
Every choice of an orthonormal frame in the d-dimensional Hilbert space of a
system corresponds to one set of all mutually commuting density matrices or,
equivalently, a classical statistical state space of the system; the quantum
state space itself can thus be profitably viewed as an SU(d) orbit of classical
state spaces, one for each orthonormal frame. We exploit this connection to
study the relative volume of separable states of a bipartite quantum system.
While the two-qubit case is studied in considerable analytic detail, for higher
dimensional systems we fall back on Monte Carlo. Several new insights seem to
emerge from our study.Comment: Essentially the published versio
Renormalized Contact Potential in Two Dimensions
We obtain for the attractive Dirac delta-function potential in
two-dimensional quantum mechanics a renormalized formulation that avoids
reference to a cutoff and running coupling constant. Dimensional transmutation
is carried out before attempting to solve the system, and leads to an
interesting eigenvalue problem in N-2 degrees of freedom (in the center of
momentum frame) when there are N particles. The effective Hamiltonian for N-2
particles has a nonlocal attractive interaction, and the Schrodinger equation
becomes an eigenvalue problem for the logarithm of this Hamiltonian. The 3-body
case is examined in detail, and in this case a variational estimate of the
ground-state energy is given.Comment: Plain Te
Solitons in a Bilocal Field Theory
We obtain a bilocal classical field theory as the large limit of the
chiral Gross--Neveu (or non--abelian Thirring) model. Exact classical solutions
that describe topological solitons are obtained. It is shown that their mass
spectrum agrees with the large limit of the spectrum of the chiral
Gross--Neveu model.Comment: Tex, 18 pages, no figure
Cosmological Ohm's law and dynamics of non-minimal electromagnetism
The origin of large-scale magnetic fields in cosmic structures and the
intergalactic medium is still poorly understood. We explore the effects of
non-minimal couplings of electromagnetism on the cosmological evolution of
currents and magnetic fields. In this context, we revisit the mildly non-linear
plasma dynamics around recombination that are known to generate weak magnetic
fields. We use the covariant approach to obtain a fully general and non-linear
evolution equation for the plasma currents and derive a generalised Ohm law
valid on large scales as well as in the presence of non-minimal couplings to
cosmological (pseudo-)scalar fields. Due to the sizeable conductivity of the
plasma and the stringent observational bounds on such couplings, we conclude
that modifications of the standard (adiabatic) evolution of magnetic fields are
severely limited in these scenarios. Even at scales well beyond a Mpc, any
departure from flux freezing behaviour is inhibited.Comment: 24 pages, 2 figures; matches version published in JCA
Atomic Compton profiles within different exchange-only theories
The Impulse Compton Profiles (CP's) J(q) and the - expectation values
for some inert gas atoms (He-Kr) are computed and compared within the
Harbola-Sahni (HS), Hartree-Fock(HF) theories and a Self Interaction Corrected
(SIC) density functional model. The Compton profiles for excited states of
Helium atom are also calculated. While the calculated CP's are found to
generally agree, they differ slightly from one another for small values of the
Compton parameter q and are in good agreement for large q values. The
expectation values within the three theories are also found to be comparable.
The HS formalism seem to mimic HF reasonably well in the momentum space,
establishing the logical consistency of the former.Comment: 15 page
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