1,221 research outputs found
Theory of Linear Spin Wave Emission from a Bloch Domain Wall
We report an analytical theory of linear emission of exchange spin waves from
a Bloch domain wall, excited by a uniform microwave magnetic field. The problem
is reduced to a one-dimensional Schr\"odinger-like equation with a
P\"oschl-Teller potential and a driving term of the same profile. The emission
of plane spin waves is observed at excitation frequencies above a threshold
value, as a result of a linear process. The height-to-width aspect ratio of the
P\"oschl-Teller profile for a domain wall is found to correspond to a local
maximum of the emission efficiency. Furthermore, for a tailored P\"oschl-Teller
potential with a variable aspect ratio, particular values of the latter can
lead to enhanced or even completely suppressed emission.Comment: added ancillary file
Recommended from our members
Molybdenum Disulfide Catalytic Coatings via Atomic Layer Deposition for Solar Hydrogen Production from Copper Gallium Diselenide Photocathodes
We demonstrate that applying atomic layer deposition-derived molybdenum disulfide (MoS2) catalytic coatings on copper gallium diselenide (CGSe) thin film absorbers can lead to efficient wide band gap photocathodes for photoelectrochemical hydrogen production. We have prepared a device that is free of precious metals, employing a CGSe absorber and a cadmium sulfide (CdS) buffer layer, a titanium dioxide (TiO2) interfacial layer, and a MoS2 catalytic layer. The resulting MoS2/TiO2/CdS/CGSe photocathode exhibits a photocurrent onset of +0.53 V vs RHE and a saturation photocurrent density of -10 mA cm-2, with stable operation for >5 h in acidic electrolyte. Spectroscopic investigations of this device architecture indicate that overlayer degradation occurs inhomogeneously, ultimately exposing the underlying CGSe absorber
Fermionic One-Loop Corrections to Soliton Energies in 1+1 Dimensions
We demonstrate an unambiguous and robust method for computing fermionic
corrections to the energies of classical background field configurations. We
consider the particular case of a sequence of background field configurations
that interpolates continuously between the trivial vacuum and a widely
separated soliton/antisoliton pair in 1+1 dimensions. Working in the continuum,
we use phase shifts, the Born approximation, and Levinson's theorem to avoid
ambiguities of renormalization procedure and boundary conditions. We carry out
the calculation analytically at both ends of the interpolation and numerically
in between, and show how the relevant physical quantities vary continuously. In
the process, we elucidate properties of the fermionic phase shifts and zero
modes.Comment: 12 pages, 4 figures, uses BoxedEPS;v2: fixed numerical error in
figure dat
SU(3) breaking in hyperon transition vector form factors
We present a calculation of the SU(3)-breaking corrections to the hyperon
transition vector form factors to in heavy baryon chiral
perturbation theory with finite-range regularisation. Both octet and decuplet
degrees of freedom are included. We formulate a chiral expansion at the
kinematic point , which can be conveniently accessed
in lattice QCD. The two unknown low-energy constants at this point are
constrained by lattice QCD simulation results for the
and transition form factors. Hence we determine
lattice-informed values of at the physical point. This work constitutes
progress towards the precise determination of from hyperon
semileptonic decays
The operator product expansion on the lattice
We investigate the Operator Product Expansion (OPE) on the lattice by
directly measuring the product (where J is the vector current) and
comparing it with the expectation values of bilinear operators. This will
determine the Wilson coefficients in the OPE from lattice data, and so give an
alternative to the conventional methods of renormalising lattice structure
function calculations. It could also give us access to higher twist quantities
such as the longitudinal structure function F_L = F_2 - 2 x F_1. We use overlap
fermions because of their improved chiral properties, which reduces the number
of possible operator mixing coefficients.Comment: 7 pages, 4 postscript figures. Contribution to Lattice 2007,
Regensbur
Quark structure from the lattice Operator Product Expansion
We have reported elsewhere in this conference on our continuing project to
determine non-perturbative Wilson coefficients on the lattice, as a step
towards a completely non-perturbative determination of the nucleon structure.
In this talk we discuss how these Wilson coefficients can be used to extract
Nachtmann moments of structure functions, using the case of off-shell
Landau-gauge quarks as a first simple example. This work is done using overlap
fermions, because their improved chiral properties reduce the difficulties due
to operator mixing.Comment: 7 pages, 3 figures. Talk given at the XXVII International Symposium
on Lattice Field Theory, July 26-31 2009, Peking University, Beijing, Chin
Energy, Central Charge, and the BPS Bound for 1+1 Dimensional Supersymmetric Solitons
We consider one-loop quantum corrections to soliton energies and central
charges in the supersymmetric and sine-Gordon models in 1+1
dimensions. In both models, we unambiguously calculate the correction to the
energy in a simple renormalization scheme and obtain ,
in agreement with previous results. Furthermore, we show that there is an
identical correction to the central charge, so that the BPS bound remains
saturated in the one-loop approximation. We extend these results to arbitrary
1+1 dimensional supersymmetric theories.Comment: 15 pages, RevTeX; v2: generalized energy result, added minor
clarifications, and fixed typos; v3: more minor clarifications and
corrections; v4: fixed factor of 2 in eq. (25); v5: fixed minor error in eq.
(55
- …