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The Top Triangle Moose
We introduce a deconstructed model that incorporates both Higgsless and
top-color mechanisms. The model alleviates the typical tension in Higgsless
models between obtaining the correct top quark mass and keeping delta-rho
small. It does so by singling out the top quark mass generation as arising from
a Yukawa coupling to an effective top-Higgs which develops a small vacuum
expectation value, while electroweak symmetry breaking results largely from a
Higgsless mechanism. As a result, the heavy partners of the SM fermions can be
light enough to be seen at the LHC
High temperature thermoelectric efficiency in Ba8Ga16Ge30
The high thermoelectric figure of merit (zT) of Ba8Ga16Ge30 makes it one of the best n-type materials for thermoelectric power generation. Here, we describe the synthesis and characterization of a Czochralski pulled single crystal of Ba8Ga16Ge30 and polycrystalline disks. Measurements of the electrical conductivity, Hall effect, specific heat, coefficient of thermal expansion, thermal conductivity, and Seebeck coefficient were performed up to 1173 K and compared with literature results. Dilatometry measurements give a coefficient of thermal expansion of 16Ă10^â6 K^â1 up to 1175 K. The trend in electronic properties with composition is typical of a heavily doped semiconductor. The maximum in the thermoelectric figure of merit is found at 1050 K with a value of 0.8. The correction of zT due to thermal expansion is not significant compared to the measurement uncertainties involved. Comparing the thermoelectric efficiency of segmented materials, the effect of compatibility makes Ba8Ga16Ge30 more efficient than the higher zT n-type materials SiGe or skutterudite CoSb3
1/S-expansion study of spin waves in a two-dimensional Heisenberg antiferromagnet
We study the effects of quantum fluctuations on excitation spectra in the
two-dimensional Heisenberg antiferromagnet by means of the 1/S expansion. We
calculate the spin-wave dispersion and the transverse dynamical structure
factor up to the second order of 1/S in comparison with inelastic neutron
scattering experiments. The spin-wave energy at momentum is found to
be about 2% smaller than that at due to the second-order
correction. In addition, we study the dimensional crossover from two dimensions
to one dimension by weakening exchange couplings in one direction. It is found
that the second-order correction becomes large with approaching the quasi-one
dimensional situation and makes the spin-wave energy approach to the des
Cloizeaux-Pearson boundary for . The transverse dynamical structure
factor is also calculated up to the second order of 1/S. It is shown that the
intensity of spin-wave peak is strongly reduced while the intensity of
three-spin-wave continuum becomes large and exceeds that of the spin-wave peak
in the quasi-one dimensional situation.Comment: 20 pages, 6 figures, revised text, added curves in Figs. 3 and 6 for
J'/J=0.075 and corrected typos in Table
Photon-pair generation by non-instantaneous spontaneous four-wave mixing
We present a general model, based on a Hamiltonian approach, for the joint
quantum state of photon pairs generated through pulsed spontaneous four-wave
mixing, including nonlinear phase-modulation and a finite material response
time. For the case of a silica fiber, it is found that the pair-production rate
depends weakly on the waveguide temperature, due to higher-order Raman
scattering events, and more strongly on pump-pair frequency detuning. From the
analytical model, a numerical scheme is derived, based on the well-known
split-step method. This scheme allows computation of joint states where
nontrivial effects are included, such as group-velocity dispersion and Raman
scattering. In this work, the numerical model is used to study the impact of
the non-instantaneous response on the pre-filtering purity of heralded single
photons. We find that for pump pulses shorter than 1 ps, a significant
detuning-dependent change in quantum-mechanical purity may be observed in
silica
Universality Class of One-Dimensional Directed Sandpile Models
A general n-state directed `sandpile' model is introduced. The stationary
properties of the n-state model are derived for n < infty, and analytical
arguments based on a central limit theorem show that the model belongs to the
universality class of the totally asymmetric Oslo model, with a crossover to
uncorrelated branching process behavior for small system sizes. Hence, the
central limit theorem allows us to identify the existence of a large
universality class of one-dimensional directed sandpile models.Comment: 4 pages, 2 figure
Screening in (2+1)D pure gauge theory at high temperatures
We compute heavy quark potentials in pure gauge at high temperatures
in dimensions and confront them with expectations emerging from
perturbative calculations.Comment: 3 pages, latex, 4 figures, uu, Contribution to LATTICE 9
Engineering spectrally unentangled photon pairs from nonlinear microring resonators through pump manipulation
The future of integrated quantum photonics relies heavily on the ability to
engineer refined methods for preparing the quantum states needed to implement
various quantum protocols. An important example of such states are
quantum-correlated photon pairs, which can be efficiently generated using
spontaneous nonlinear processes in integrated microring-resonator structures.
In this work, we propose a method for generating spectrally unentangled photon
pairs from a standard microring resonator. The method utilizes interference
between a primary and a delayed secondary pump pulse to effectively increase
the pump spectral width inside the cavity. This enables on-chip generation of
heralded single photons with state purities in excess of 99 % without spectral
filtering.Comment: 5 pages, 5 figure
Parity violation and the nature of charges
The origin of parity violation in physics is still unknown. At the present
time, it is introduced in the theory by requiring that the SU(2) subgroup
entering the description of interactions involves the left components. In the
present contribution, one elaborates upon a suggestion made by Landau that
particles and antiparticles could be like "stereo-isomeric" molecules, which
would naturally provides parity violation. Particles and antiparticles could
thus be combinations of the parity doublets associated with a chiral symmetry
realized in the Wigner-Weyl mode. Consequences of such a description and the
possible problems it could raise are examined.Comment: 3 pages, contribution to the 3rd international workshop: "From parity
violation to hadronic structure and more ..." (PAVI06), to appear in the
proceedings (EPJA
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