1,659 research outputs found
Musical minds
Comments on the idea that music might be a process of communication between composer and listener
The transition temperature of the dilute interacting Bose gas
We show that the critical temperature of a uniform dilute Bose gas must
increase linearly with the s-wave scattering length describing the repulsion
between the particles. Because of infrared divergences, the magnitude of the
shift cannot be obtained from perturbation theory, even in the weak coupling
regime; rather, it is proportional to the size of the critical region in
momentum space. By means of a self-consistent calculation of the quasiparticle
spectrum at low momenta at the transition, we find an estimate of the effect in
reasonable agreement with numerical simulations.Comment: 4 pages, Revtex, to be published in Physical Review Letter
Spontaneous and stimulated emission tuning characteristics of a Josephson junction in a microcavity
We have investigated theoretically the tuning characteristics of a Josephson
junction within a microcavity for one-photon spontaneous emission and for
one-photon and two-photon stimulated emission. For spontaneous emission, we
have established the linear relationship between the magnetic induction and the
voltage needed to tune the system to emit at resonant frequencies. For
stimulated emission, we have found an oscillatory dependence of the emission
rate on the initial Cooper pair phase difference and the phase of the applied
field. Under specific conditions, we have also calculated the values of the
applied radiation amplitude for the first few emission maxima of the system and
for the first five junction-cavity resonances for each process. Since the
emission of photons can be controlled, it may be possible to use such a system
to produce photons on demand. Such sources will have applications in the fields
of quantum cryptography, communications and computation
COVID-19 and Food Insecurity Impacts: A Follow Up Vermont Study
This brief report details the results from a follow-up survey of 1,236 Vermonters in June 2020, after an initial survey in March/April 2020 focused on the impact of COVID-19 on food access and security. The key results include: 1) Nearly 1 in 4 respondents (23%) were classified as food insecure in June, a reported 22% decrease since March, but higher than before COVID-19. 2) People of color, those without a college degree, those with a job loss, households with children, women, and younger people had greater odds of experiencing food insecurity. 3) The majority of respondent households had experienced some job loss or disruption in the last 30 days, and were still experiencing job changes at the time of the survey. 4) People receiving unemployment were significantly more likely to be using multiple food assistance programs compared to others. 5) Respondents significantly increased use of food assistance programs since March. 6) Vermonters today have greater concerns about food becoming more expensive and possible loss of food assistance programs compared to June. 7) Vermonters today are facing fewer perceived challenges in food access and have fewer worries about food availability compared to March
Food and Job Insecurity in Vermont During COVID-19 Infographic
This infographic details the summary results from a second Vermont survey on food and job insecurity in Vermont during COVID-19 in March and June 2020. Key results include: 1) Nearly 1 in 4 Vermonters experience food insecurity in June 2020; 2) People of color, those without a college degree, with job disruption, with children, and women were more likely to be food insecure; 3) More than 50% of Vermonters experienced job loss or disruption, and 20% received unemployment in June 2020; 4) Use of food assistance programs rose significantly between March 2020 and June 2020
Probing Pseudogap by Josephson Tunneling
We propose here an experiment aimed to determine whether there are
superconducting pairing fluctuations in the pseudogap regime of the high-
materials. In the experimental setup, two samples above are brought into
contact at a single point and the differential AC conductivity in the presence
of a constant applied bias voltage between the samples, , should be
measured. We argue the the pairing fluctuations will produce randomly
fluctuating Josephson current with zero mean, however the current-current
correlator will have a characteristic frequency given by Josephson frequency
. We predict that the differential AC conductivity
should have a peak at the Josephson frequency with the width determined by the
phase fluctuations time.Comment: 4 pages, 2 eps figure
Response of thin-film SQUIDs to applied fields and vortex fields: Linear SQUIDs
In this paper we analyze the properties of a dc SQUID when the London
penetration depth \lambda is larger than the superconducting film thickness d.
We present equations that govern the static behavior for arbitrary values of
\Lambda = \lambda^2/d relative to the linear dimensions of the SQUID. The
SQUID's critical current I_c depends upon the effective flux \Phi, the magnetic
flux through a contour surrounding the central hole plus a term proportional to
the line integral of the current density around this contour. While it is well
known that the SQUID inductance depends upon \Lambda, we show here that the
focusing of magnetic flux from applied fields and vortex-generated fields into
the central hole of the SQUID also depends upon \Lambda. We apply this
formalism to the simplest case of a linear SQUID of width 2w, consisting of a
coplanar pair of long superconducting strips of separation 2a, connected by two
small Josephson junctions to a superconducting current-input lead at one end
and by a superconducting lead at the other end. The central region of this
SQUID shares many properties with a superconducting coplanar stripline. We
calculate magnetic-field and current-density profiles, the inductance
(including both geometric and kinetic inductances), magnetic moments, and the
effective area as a function of \Lambda/w and a/w.Comment: 18 pages, 20 figures, revised for Phys. Rev. B, the main revisions
being to denote the effective flux by \Phi rather than
Superconducting Plasma Excitation at Microwave Frequencies in Parallel Magnetic Fields in
Josephson plasma resonance has been studied in a wide microwave frequency
range between 10 and 52 GHz in a magnetic field parallel to the -plane in
under-doped \BI. Above about 30 GHz two resonance modes were observed: one
(LT mode) appears at low temperatures and another (HT mode) at higher
temperatures, leaving a temperature gap between two regions. These two
resonance modes exhibit a sharp contrast each other both on temperture and
magnetic field dependences and show distinct characters different entirely from
the c-axis Josephson plasma resonance. From temperature and field scan
experiments at various frequencies it is suggested that the LT mode can be
attributed to the coupled Josephson plasma mode with Josephson vortices, while
the HT mode is a new plasma mode associated possibly with the periodic array of
Josephson vortices.Comment: submitted to Physica C (Prceedings of Plasma2000, Sendai
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