1,077 research outputs found
Study of Electromagnetically Induced Transparency using long-lived Singlet States
The long-lived singlet states are useful to study a variety of interesting
quantum phenomena. In this work we study electromagnetically induced
transparency using a two-qubit system. The singlet state acts as a `dark state'
which does not absorb a probe radiation in the presence of a control radiation.
Further we demonstrate that the simultaneous irradiation of probe and control
radiations acts as a dynamical decoupling preserving the singlet state at
higher correlation for longer durations.Comment: 4 pages, 4 figure
Dirty Weyl semimetals: Stability, phase transition and quantum criticality
We study the stability of three-dimensional incompressible Weyl semimetals in
the presence of random quenched charge impurities. Combining numerical analysis
and scaling theory we show that in the presence of sufficiently weak randomness
(i) Weyl semimetal remains stable, while (ii) double-Weyl semimetal gives rise
to compressible diffusive metal where the mean density of states at zero energy
is finite. At stronger disorder, Weyl semimetal undergoes a quantum phase
transition and enter into a metallic phase. Mean density of states at zero
energy serves as the order parameter and displays single-parameter scaling
across such disorder driven quantum phase transition. We numerically determine
various exponents at the critical point, which appear to be insensitive to the
number of Weyl pairs. We also extract the extent of the quantum critical regime
in disordered Weyl semimetal and the phase diagram of dirty double Weyl
semimetal at finite energies.Comment: 5 pages and 5 figures (Supplementary: 6 pages and 5 figure):
Published version, added discussion, new results and reference
Relic density and PAMELA events in a heavy wino dark matter model with Sommerfeld effect
In a wino LSP scenario the annihilation cross section of winos
gravitationally bound in galaxies can be boosted by a Sommerfeld enhancement
factor which arises due to the ladder of exchanged W bosons between the initial
states. The boost factor obtained can be in the range S ~ 10^4 if the mass is
close to the resonance value of M ~ 4 TeV. In this paper we show that if one
takes into account the Sommerfeld enhancement in the relic abundance
calculation then the correct relic density is obtained for 4 TeV wino mass due
to the enhanced annihilation after their kinetic decoupling. At the same time
the Sommerfeld enhancement in the \chi \chi --> W^+ W^- annihilation channel is
sufficient to explain the positron flux seen in PAMELA data without
significantly exceeding the observed antiproton signal. We also show that (e^-
+ e^+) and gamma ray signals are broadly compatible with the Fermi-LAT
observations. In conclusion we show that a 4 TeV wino DM can explain the
positron and antiproton fluxes observed by PAMELA and at the same time give a
thermal relic abundance of CDM consistent with WMAP observations.Comment: 24 pages, 12 figures, 1 table; title corrected in arxiv metadat
Hepatitis A presenting as bilateral pleural effusion in two pediatric patients
Hepatitis A is a common disease with benign and self-limiting outcome; however, very rarely it is associated with pleural effusion. We present two cases, one 6-year-old girl and another 4-year-old boy, both of whom presented with bilateral pleural effusion associated with hepatitis A. Both children were managed according to protocols for hepatitis A, following which, the pleural effusion resolved spontaneously. Pleural effusion in hepatitis A is benign and self-limiting. It does not need any separate test or treatment
Higgsino Dark Matter in Nonuniversal Gaugino Mass Models
We study two simple and well motivated nonuniversal gaugino mass models,
which predict higgsino dark matter. One can account for the observed dark
matter relic density along with the observed Higgs boson mass of ~ 125 GeV over
a large region of the parameter space of each model, corresponding to higgsino
mass of ~ 1 TeV. In each case this parameter region covers the gluino mass
range of 2-3 TeV, parts of which can be probed by the 14 TeV LHC experiments.
We study these model predictions for LHC in brief and for dark matter detection
experiments in greater detail.Comment: 35 pages, 11 figures, pdflatex, new references and a few relevant
decay branching ratios added in two tables. Version to appear in Phys Rev
Path Planning of Mobile Agents using AI Technique
In this paper, we study coordinated motion in a swarm robotic system, called a swarm-bot. A swarm-bot is a self-assembling and self-organizing. Artifact composed of a swarm of s-bots, mobile robots with the ability to connect to and is connect from each other. The swarm-bot concept is particularly suited for tasks that require all-terrain navigation abilities, such as space exploration or rescue in collapsed buildings. As a first step toward the development of more complex control strategies, we investigate the case in which a swarm-bot has to explore an arena while avoiding falling into holes.
In such a scenario, individual s-bots have sensory–motor limitations that prevent them navigating efficiently. These limitations can be overcome if the s-bots are made to cooperate. In particular, we exploit the s-bots’ ability to physically connect to each other. In order to synthesize the s-bots’ controller, we rely on artificial evolution, which we show to be a powerful tool for the production of simple and effective solutions to the hole avoidance task
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