19,270 research outputs found
Non-adiabatically detecting the geometric phase of the macroscopic quantum state with symmetric SQUID
We give a simple way to detect the geometric phase shift and the conditional
geometric phase shift with Josephson junction system. Comparing with the
previous work(Falcl G, Fazio R, Palma G.M., Siewert J and Verdal V, {\it
Nature} {\bf 407}, 355(2000)), our scheme has two advantages. We use the
non-adiabatic operation, thus the detection is less affected by the
decoherence. Also, we take the time evolution on zero dynamic phase loop, we
need not take any extra operation to cancel the dynamic phase.Comment: 8 pages, 4 figure
Strong decays of and
With the identification of () as the (,
) doublet in the heavy quark effective field theory, we derive the light
cone QCD sum rule for the coupling of eta meson with and
. Through mixing we calculate their pionic
decay widths, which are consistent with the experimental values (or upper
limits). Combining the radiative decay widths derived by Colangelo, Fazio and
Ozpineci in the same framework, we conclude that the decay patterns of
strongly support their interpretation as ordinary mesons.Comment: Comments and suggestions welcome
A Lower-Limit Flux for the Extragalactic Background Light
... A strict lower-limit flux for the evolving extragalactic background light
(and in particular the cosmic infrared background) has been calculated up to
redshift of 5. The computed flux is below the existing upper limits from direct
observations, and in agreement with all existing limits derived from very-high
energy gamma-ray observations. The corrected spectra are still in agreement
with simple theoretical predictions. The derived strict lower-limit EBL flux is
very close to the upper limits from gamma-ray observations. This is true for
the present day EBL but also for the diffuse flux at higher redshift. If future
detections of high redshift gamma-ray sources require a lower EBL flux than
derived here, the physics assumptions used to derive the upper limits have to
be revised. The lower-limit EBL model is not only needed for absorption
features in AGN and other gamma-ray sources but is also essential when
alternative particle processes are tested, which could prevent the high energy
gamma-rays from being absorbed. It can also be used for a quaranteed
interaction of cosmic-ray particles. The model is available online.Comment: 12 pages, 6 figures, accepted by A&
Identifying through its decay modes
We study how to assign the recently observed meson to an
appropriate level of the spectrum by the analysis of its decay modes
in final states comprising a light pseudoscalar meson. We use an effective
lagrangian approach with heavy quark and chiral symmetries, obtaining that the
measurement of the decay width would allow to distinguish between two
possible assignments.Comment: RevTex, 6 pages - references adde
Dust composition and mass-loss return from the luminous blue variable R71 in the LMC
We present an analysis of mid-and far-infrared (IR) spectrum and spectral
energy distribution (SED) of the LBV R71 in the LMC.This work aims to
understand the overall contribution of high-mass LBVs to the total dust-mass
budget of the interstellar medium (ISM) of the LMC and compare this with the
contribution from low-mass asymptotic giant branch (AGB) stars. As a case
study, we analyze the SED of R71. We compiled all the available photometric and
spectroscopic observational fluxes from various telescopes for a wide
wavelength range (0.36 -- 250\,m). We determined the dust composition from
the spectroscopic data, and derived the ejected dust mass, dust mass-loss rate,
and other dust shell properties by modeling the SED of R71. We noted nine
spectral features in the dust shell of R71 by analyzing Spitzer spectroscopic
data. Among these, we identified three new crystalline silicate features. We
computed our model spectrum by using 3D radiative transfer code MCMax. Our
model calculation shows that dust is dominated by amorphous silicates, with
some crystalline silicates, metallic iron, and a very tiny amount of polycyclic
aromatic hydrocarbon (PAH) molecules. The presence of both silicates and PAHs
indicates that the dust has a mixed chemistry. We derived a dust mass of 0.01
M, from which we arrive at a total ejected mass of 5
M. This implies a time-averaged dust mass-loss rate of
2.510 M\,yr with an explosion about 4000 years
ago. We assume that the other five confirmed dusty LBVs in the LMC loose mass
at a similar rate, and estimate the total contribution to the mass budget of
the LMC to be 10 M\,yr, which is comparable to
the contribution by all the AGB stars in the LMC. Based on our analysis on R71,
we speculate that LBVs as a class may be an important dust source in the ISM of
the LMC.Comment: 10 pages, 6 figures, 2 table
B -> X_u l nu decay distributions to order alpha_s
An analytic result for the O(alpha_s corrections to the triple differential B
-> X_u l nu decay rate is presented, to leading order in the heavy-quark
expansion. This is relevant for computing partially integrated decay
distributions with arbitrary cuts on kinematic variables. Several double and
single differential distributions are derived, most of which generalize known
results. In particular, an analytic result for the O(alpha_s) corrections to
the hadronic invariant mass spectrum is presented. The effects of Fermi motion,
which are important for the description of decay spectra close to infrared
sensitive regions, are included. The behaviour of perturbation theory in the
region of time-like momenta is also investigatedComment: 24 pages, 11 figures, 1 typo in eq.(5.4) corrected; version published
in JHEP06(1999)01
Quantum Communication through Spin Chain Dynamics: an Introductory Overview
We present an introductory overview of the use of spin chains as quantum
wires, which has recently developed into a topic of lively interest. The
principal motivation is in connecting quantum registers without resorting to
optics. A spin chain is a permanently coupled 1D system of spins. When one
places a quantum state on one end of it, the state will be dynamically
transmitted to the other end with some efficiency if the spins are coupled by
an exchange interaction. No external modulations or measurements on the body of
the chain, except perhaps at the very ends, is required for this purpose. For
the simplest (uniformly coupled) chain and the simplest encoding (single qubit
encoding), however, dispersion reduces the quality of transfer. We present a
variety of alternatives proposed by various groups to achieve perfect quantum
state transfer through spin chains. We conclude with a brief discussion of the
various directions in which the topic is developing.Comment: Material covered till Dec 200
A Rare Presentation of Crohn's Disease
Free peritoneal perforation is a rare complication of Crohn's disease with a report of only 100 cases in the literature. It needs an emergency exploration and an unaware general surgeon is confounded in intraoperative decision-making. We present our experience when this rarity struck us in a district hospital and briefly review the guidelines of optimal management of this complication of Crohn's disease
Superconductor-insulator duality for the array of Josephson wires
We propose novel model system for the studies of superconductor-insulator
transitions, which is a regular lattice, whose each link consists of
Josephson-junction chain of junctions in sequence. The theory of such
an array is developed for the case of semiclassical junctions with the
Josephson energy large compared to the junctions's Coulomb energy .
Exact duality transformation is derived, which transforms the Hamiltonian of
the proposed model into a standard Hamiltonian of JJ array. The nature of the
ground state is controlled (in the absence of random offset charges) by the
parameter , with superconductive state
corresponding to small . The values of are calculated for
magnetic frustrations and . Temperature of superconductive
transition and is estimated for the same values of . In
presence of strong random offset charges, the T=0 phase diagram is controlled
by the parameter ; we estimated critical value
.Comment: 5 pages, 2 figure
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