10,360 research outputs found
Convergence of Monte Carlo Simulations to Equilibrium
We give two direct, elementary proofs that a Monte Carlo simulation converges
to equilibrium provided that appropriate conditions are satisfied. The first
proof requires detailed balance while the second is quite general.Comment: 4 pages. v2: published versio
A test of local Lorentz invariance with Compton scattering asymmetry
We report on a measurement of the constancy and anisotropy of the speed of
light relative to the electrons in photon-electron scattering. We used the
Compton scattering asymmetry measured by the new Compton polarimeter in Hall~C
at Jefferson Lab to test for deviations from unity of the vacuum refractive
index (). For photon energies in the range of 9 - 46 MeV, we obtain a new
limit of . In addition, the absence of sidereal
variation over the six month period of the measurement constrains any
anisotropies in the speed of light. These constitute the first study of Lorentz
invariance using Compton asymmetry. Within the minimal standard model extension
framework, our result yield limits on the photon and electron coefficients
, and .
Although, these limits are several orders of magnitude larger than the current
best limits, they demonstrate the feasibility of using Compton asymmetry for
tests of Lorentz invariance. Future parity violating electron scattering
experiments at Jefferson Lab will use higher energy electrons enabling better
constraints.Comment: 7 pages, 5 figure
Self similar Barkhausen noise in magnetic domain wall motion
A model for domain wall motion in ferromagnets is analyzed. Long-range
magnetic dipolar interactions are shown to give rise to self-similar dynamics
when the external magnetic field is increased adiabatically. The power spectrum
of the resultant Barkhausen noise is of the form , where
can be estimated from the critical exponents for interface
depinning in random media.Comment: 7 pages, RevTex. To appear in Phys. Rev. Let
Supercurrent as a Probe for Topological Superconductivity in Magnetic Adatom Chains
A magnetic adatom chain, proximity coupled to a conventional superconductor
with spin-orbit coupling, exhibits locally an odd-parity, spin-triplet pairing
amplitude. We show that the singlet-triplet junction, thus formed, leads to a
net spin accumulation in the near vicinity of the chain. The accumulated spins
are polarized along the direction of the local -vector for triplet
pairing and generate an enhanced persistent current flowing around the chain.
The spin polarization and the "supercurrent" reverse their directions beyond a
critical exchange coupling strength at which the singlet superconducting order
changes its sign on the chain. The current is strongly enhanced in the
topological superconducting regime where Majorana bound states appear at the
chain ends. The current and the spin profile offer alternative routes to
characterize the topological superconducting state in adatom chains and
islands.Comment: 5 pages, 3 figures, 5 pages of supplemental material
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