1,328 research outputs found
Sparticle masses in deflected mirage mediation
We discuss the sparticle mass patterns that can be realized in deflected
mirage mediation scenario of supersymmetry breaking, in which the moduli,
anomaly, and gauge mediations all contribute to the MSSM soft parameters.
Analytic expression of low energy soft parameters and also the sfermion mass
sum rules are derived, which can be used to interpret the experimentally
measured sparticle masses within the framework of the most general mixed
moduli-gauge-anomaly mediation. Phenomenological aspects of some specific
examples are also discussed.Comment: 43 pages, 17 figures, references adde
Scattering by impurity-induced order parameter ``holes'' in d-wave superconductors
Nonmagnetic impurities in d-wave superconductors cause strong local
suppressions of the order parameter. We investigate the observable effects of
the scatterigng off such suppressions in bulk samples by treating the order
parameter "hole" as a pointlike off-diagonal scatterer treated within a
self-consistent t-matrix approximation. Strong scattering potentials lead to a
finite-energy spectral feature in the d-wave "impurity band", the observable
effects of which include enhanced low-temperature microwave power absorption
and a stronger sensitivity of the London penetration depth to disorder than
found previously in simpler ``dirty'' d-wave models.Comment: 5 pp. Revtex including 4 postscript figures, submitted to Phys. Rev.
Effect of Nyquist Noise on the Nyquist Dephasing Rate in 2d Electron Systems
We measure the effect of externally applied broadband Nyquist noise on the
intrinsic Nyquist dephasing rate of electrons in a two-dimensional electron gas
at low temperatures. Within the measurement error, the phase coherence time is
unaffected by the externally applied Nyquist noise, including applied noise
temperatures of up to 300 K. The amplitude of the applied Nyquist noise from
100 MHz to 10 GHz is quantitatively determined in the same experiment using a
microwave network analyzer.Comment: 5 pages, 4 figures. Author affiliation clarified; acknowledgements
modified. Replacement reason clarifie
Nuclear spin-lattice relaxation rate in the D+iD superconducting state: implications for CoO superconductor
We calculated the nuclear spin-lattice relaxation rate for the D+iD
superconducting state with impurities. We found that small amount of unitary
impurities quickly produces the residual density of states inside the gap. As a
result, the T-linear behavior in 1/T is observed at low temperatures. Our
results show that the D+iD pairing symmetry of the superconducting state of
NaCoOH O is compatible with recent Co 1/T
experiments of several groups.Comment: 5 pages, 4 figures, minor change
Poincare Invariant Algebra From Instant to Light-Front Quantization
We present the Poincare algebra interpolating between instant and light-front
time quantizations. The angular momentum operators satisfying SU(2) algebra are
constructed in an arbitrary interpolation angle and shown to be identical to
the ordinary angular momentum and Leutwyler-Stern angular momentum in the
instant and light-front quantization limits, respectively. The exchange of the
dynamical role between the transverse angular mometum and the boost operators
is manifest in our newly constructed algebra.Comment: 21 pages, 3 figures, 1 tabl
Transition Form Factors between Pseudoscalar and Vector Mesons in Light-Front Dynamics
We study the transition form factors between pseudoscalar and vector mesons
using a covariant fermion field theory model in dimensions. Performing
the light-front calculation in the frame in parallel with the
manifestly covariant calculation, we note that the suspected nonvanishing
zero-mode contribution to the light-front current does not exist in our
analysis of transition form factors. We also perform the light-front
calculation in a purely longitudinal frame and confirm that the form
factors obtained directly from the timelike region are identical to the ones
obtained by the analytic continuation from the spacelike region. Our results
for the decay process satisfy the constraints on the
heavy-to-heavy semileptonic decays imposed by the flavor independence in the
heavy quark limit.Comment: 20 pages, 14 figure
Angular Conditions,Relations between Breit and Light-Front Frames, and Subleading Power Corrections
We analyze the current matrix elements in the general collinear (Breit)
frames and find the relation between the ordinary (or canonical) helicity
amplitudes and the light-front helicity amplitudes. Using the conservation of
angular momentum, we derive a general angular condition which should be
satisfied by the light-front helicity amplitudes for any spin system. In
addition, we obtain the light-front parity and time-reversal relations for the
light-front helicity amplitudes. Applying these relations to the spin-1 form
factor analysis, we note that the general angular condition relating the five
helicity amplitudes is reduced to the usual angular condition relating the four
helicity amplitudes due to the light-front time-reversal condition. We make
some comments on the consequences of the angular condition for the analysis of
the high- deuteron electromagnetic form factors, and we further apply the
general angular condition to the electromagnetic transition between spin-1/2
and spin-3/2 systems and find a relation useful for the analysis of the
N- transition form factors. We also discuss the scaling law and the
subleading power corrections in the Breit and light-front frames.Comment: 24 pages,2 figure
Thermoelectric power of MgBBe
We investigated thermoelectric power of MgBBe (,
0.2, 0.3, 0.4, and 0.6). decreases systematically with , suggesting
that the hole density increases. Our band calculation shows that the increase
occurs in the -band. With the hole-doping, decreases.
Implication of this phenomenon is discussed within the BCS framework. While the
Mott formula explains only the linear part of at low temperature,
incorporation of electron-phonon interaction enables us to explain over
wide temperature range including the anomalous behavior at high temperature.Comment: 4 pages, 4 figure
Distinguishing d-wave from highly anisotropic s-wave superconductors
Systematic impurity doping in the Cu-O plane of the hole-doped cuprate
superconductors may allow one to decide between unconvention al ("d-wave") and
anisotropic conventional ("s-wave") states as possible candidates for the order
parameter in these materials. We show that potential scattering of any strength
always increases the gap minima of such s-wave states, leading to activated
behavior in temperature with characteristic impurity concentration dependence
in observable quantities such as the penetration depth. A magnetic component to
the scattering may destroy the energy gap and give rise to conventional gapless
behavior, or lead to a nonmonotonic dependence of the gap on impurity
concentration. We discuss how experiments constrain this analysis.Comment: 5 page
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