108,873 research outputs found
A New S-S' Pair Creation Rate Expression Improving Upon Zener Curves for I-E Plots
To simplify phenomenology modeling used for charge density wave
(CDW)transport, we apply a wavefunctional formulation of tunneling Hamiltonians
to a physical transport problem characterized by a perturbed washboard
potential. To do so, we consider tunneing between states that are
wavefunctionals of a scalar quantum field. I-E curves that match Zener curves -
used to fit data experimentally with wavefunctionals congruent with the false
vacuum hypothesis. This has a very strong convergence with electron-positron
pair production representations.The similarities in plot behavior of the
current values after the threshold electric field values argue in favor of the
Bardeen pinning gap paradigm proposed for quasi-one-dimensional metallic
transport problems.Comment: 22 pages,6 figures, and extensive editing of certain segments.Paper
has been revised due to acceptance by World press scientific MPLB journal.
This is word version of file which has been submitted to MPLBs editor for
final proofing. Due for publication perhaps in mid spring to early summer
200
Expansions of the real field by open sets: definability versus interpretability
An open set U of the real numbers R is produced such that the expansion
(R,+,x,U) of the real field by U defines a Borel isomorph of (R,+,x,N) but does
not define N. It follows that (R,+,x,U) defines sets in every level of the
projective hierarchy but does not define all projective sets. This result is
elaborated in various ways that involve geometric measure theory and working
over o-minimal expansions of (R,+,x). In particular, there is a Cantor subset K
of R such that for every exponentially bounded o-minimal expansion M of
(R,+,x), every subset of R definable in (M,K) either has interior or is
Hausdorff null.Comment: 14 page
Measurement-dependent corrections to work distributions arising from quantum coherences
For a quantum system undergoing a unitary process work is commonly defined
based on the Two Projective Measurement (TPM) protocol which measures the
energies of the system before and after the process. However, it is well known
that projective measurements disregard quantum coherences of the system with
respect to the energy basis, thus removing potential quantum signatures in the
work distribution. Here we consider weak measurements of the system's energy
difference and establish corrections to work averages arising from initial
system coherences. We discuss two weak measurement protocols that couple the
system to a detector, prepared and measured either in the momentum or the
position eigenstates. Work averages are derived for when the system starts in
the proper thermal state versus when the initial system state is a pure state
with thermal diagonal elements and coherences characterised by a set of phases.
We show that by controlling only the phase differences between the energy
eigenstate contributions in the system's initial pure state, the average work
done during the same unitary process can be controlled. By changing the phases
alone one can toggle from regimes where the systems absorbs energy, i.e. a work
cost, to the ones where it emits energy, i.e. work can be drawn. This suggests
that the coherences are additional resources that can be used to manipulate or
store energy in a quantum system.Comment: 9 pages, 3 figure
An open question: Are topological arguments helpful in setting initial conditions for transport problems in condensed matter physics?
The tunneling Hamiltonian is a proven method to treat particle tunneling
between different states represented as wavefunctions in many-body physics. Our
problem is how to apply a wave functional formulation of tunneling Hamiltonians
to a driven sine-Gordon system. We apply a generalization of the tunneling
Hamiltonian to charge density wave (CDW) transport problems in which we
consider tunneling between states that are wavefunctionals of a scalar quantum
field. We present derived I-E curves that match Zenier curves used to fit data
experimentally with wavefunctionals congruent with the false vacuum hypothesis.
THe open question is whether the coefficients picked in both the
wavefunctionals and the magnitude of the coefficents of the driven sine Gordon
physical system should be picked by topological charge arguements that in
principle appear to assign values that have a tie in with the false vacuum
hypothesis first presented by Sidney ColemanComment: 17 pages, 4 figures (1a to 2b) on two pages. Specific emphasis on if
or not topological arguements a la Trodden, Su et al add to formulation of
condensed matter transport problem
Thermal distortions of non-Gaussian beams in Fabry–Perot cavities
Thermal effects are already important in currently operating interferometric gravitational wave detectors. Planned upgrades of these detectors involve increasing optical power to combat quantum shot noise. We consider the ramifications of this increased power for one particular class of laser beams—wide, flat-topped, mesa beams. In particular we model a single mesa beam Fabry–Perot cavity having thermoelastically deformed mirrors. We calculate the intensity profile of the fundamental cavity eigenmode in the presence of thermal perturbations, and the associated changes in thermal noise. We also outline an idealized method of correcting for such effects. At each stage we contrast our results with those of a comparable Gaussian beam cavity. Although we focus on mesa beams the techniques described are applicable to any azimuthally symmetric system
Transonic aerodynamic and aeroelastic characteristics of a variable sweep wing
The flow over the B-1 wing is studied computationally, including the aeroelastic response of the wing. Computed results are compared with results from wind tunnel and flight tests for both low-sweep and high-sweep cases, at 25.0 deg. and 67.5 deg., respectively, for selected transonic Mach numbers. The aerodynamic and aeroelastic computations are made by using the transonic unsteady code ATRAN3S. Steady aerodynamic computations compare well with wind tunnel results for the 25.0 deg. sweep case and also for small angles of attack at the 67.5 deg. sweep case. The aeroelastic response results show that the wing is stable at the low sweep angle for the calculation at the Mach number at which there is a shock wave. In the higher sweep case, for the higher angle of attack at which oscillations were observed in the flight and wind tunnel tests, the calculations do not show any shock waves. Their absence lends support to the hypothesis that the observed oscillations are due to the presence of leading edge separation vortices and are not due to shock wave motion as was previously proposed
Food insecurity in veteran households: findings from nationally representative data
OBJECTIVE: The present study is the first to use nationally representative data to compare rates of food insecurity among households with veterans of the US Armed Forces and non-veteran households. DESIGN: We used data from the 2005-2013 waves of the Current Population Survey - Food Security Supplement to identify rates of food insecurity and very low food security in veteran and non-veteran households. We estimated the odds and probability of food insecurity in veteran and non-veteran households in uncontrolled and controlled models. We replicated these results after separating veteran households by their most recent period of service. We weighted models to create nationally representative estimates. SETTING: Nationally representative data from the 2005-2013 waves of the Current Population Survey - Food Security Supplement. SUBJECTS: US households (n 388 680). RESULTS: Uncontrolled models found much lower rates of food insecurity (8·4 %) and very low food security (3·3 %) among veteran households than in non-veteran households (14·4 % and 5·4 %, respectively), with particularly low rates among households with older veterans. After adjustment, average rates of food insecurity and very low food security were not significantly different for veteran households. However, the probability of food insecurity was significantly higher among some recent veterans and significantly lower for those who served during the Vietnam War. CONCLUSIONS: Although adjusting eliminated many differences between veteran and non-veteran households, veterans who served from 1975 and onwards may be at higher risk for food insecurity and should be the recipients of targeted outreach to improve nutritional outcomes
Extended Feynman Formula for the Harmonic Oscillator by the Discrete Time Method
We calculate the Feynman formula for the harmonic oscillator beyond and at
caustics by the discrete formulation of path integral. The extension has been
made by some authors, however, it is not obtained by the method which we
consider the most reliable regularization of path integral. It is shown that
this method leads to the result with, especially at caustics, more rigorous
derivation than previous.Comment: 9 page
Break in the VHE spectrum of PG 1553+113: new upper limit on its redshift?
PG 1553+113 is a known BL Lac object, newly detected in the GeV-TeV energy
range by H.E.S.S and MAGIC. The redshift of this source is unknown and a lower
limit of was recently estimated. The very high energy (VHE) spectrum
of PG 1553+113 is attenuated due to the absorption by the low energy photon
field of the extragalactic background light (EBL). Here we correct the combined
H.E.S.S and MAGIC spectrum of PG 1553+113 for this absorption assuming a
minimum density of the evolving EBL. We use an argument that the intrinsic
photon index cannot be harder than and derive an upper limit on
the redshift of . Moreover, we find that a redshift above
implies a possible break of the intrinsic spectrum at about 200 GeV. Assuming
that such a break is absent, we derive a much stronger upper limit of . Alternatively, this break might be attributed to an additional emission
component in the jet of PG 1553+113. This would be the first evidence for a
second component is detected in the VHE spectrum of a blazar.Comment: revised version submitted to Ap
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