25,006 research outputs found
Little Higgs Model Completed with a Chiral Fermionic Sector
The implementation of the little Higgs mechanism to solve the hierarchy
problem provides an interesting guiding principle to build particle physics
models beyond the electroweak scale. Most model building works, however, pay
not much attention to the fermionic sector. Through a case example, we
illustrate how a complete and consistent fermionic sector of the TeV effective
field theory may actually be largely dictated by the gauge structure of the
model. The completed fermionic sector has specific flavor physics structure,
and many phenomenological constraints on the model can thus be obtained beyond
gauge, Higgs, and top physics. We take a first look on some of the quark sector
constraints.Comment: 14 revtex pages with no figure, largely a re-written version of
hep-ph/0307250 with elaboration on flavor sector FCNC constraints; accepted
for publication in Phys.Rev.
X-ray Localization of the Globular Cluster G1 with XMM-Newton
We present an accurate X-ray position of the massive globular cluster G1 by
using XMM-Newton and the Hubble Space Telescope (HST). The X-ray emission of G1
has been detected recently with XMM-Newton. There are two possibilities for the
origin of the X-ray emission. It can be either due to accretion of the central
intermediate-mass black hole, or by ordinary low-mass X-ray binaries. The
precise location of the X-ray emission might distinguish between these two
scenarios. By refining the astrometry of the XMM-Newton and HST data, we
reduced the XMM-Newton error circle to 1.5". Despite the smaller error circle,
the precision is not sufficient to distinguish an intermediate-mass black hole
and luminous low-mass X-ray binaries. This result, however, suggests that
future Chandra observations may reveal the origin of the X-ray emission.Comment: 4 pages, 2 figures; accepted for publication in Ap
Time-Periodic Solutions of the Einstein's Field Equations II
In this paper, we construct several kinds of new time-periodic solutions of
the vacuum Einstein's field equations whose Riemann curvature tensors vanish,
keep finite or take the infinity at some points in these space-times,
respectively. The singularities of these new time-periodic solutions are
investigated and some new physical phenomena are found. The applications of
these solutions in modern cosmology and general relativity can be expected.Comment: 10 pages, 1 figur
New Results for Diffusion in Lorentz Lattice Gas Cellular Automata
New calculations to over ten million time steps have revealed a more complex
diffusive behavior than previously reported, of a point particle on a square
and triangular lattice randomly occupied by mirror or rotator scatterers. For
the square lattice fully occupied by mirrors where extended closed particle
orbits occur, anomalous diffusion was still found. However, for a not fully
occupied lattice the super diffusion, first noticed by Owczarek and Prellberg
for a particular concentration, obtains for all concentrations. For the square
lattice occupied by rotators and the triangular lattice occupied by mirrors or
rotators, an absence of diffusion (trapping) was found for all concentrations,
except on critical lines, where anomalous diffusion (extended closed orbits)
occurs and hyperscaling holds for all closed orbits with {\em universal}
exponents and . Only one point on these critical lines can be related to a
corresponding percolation problem. The questions arise therefore whether the
other critical points can be mapped onto a new percolation-like problem, and of
the dynamical significance of hyperscaling.Comment: 52 pages, including 18 figures on the last 22 pages, email:
[email protected]
Radiative corrections to the Casimir force and effective field theories
Radiative corrections to the Casimir force between two parallel plates are
considered in both scalar field theory of one massless and one massive field
and in QED. Full calculations are contrasted with calculations based on
employing ``boundary-free'' effective field theories. The difference between
two previous results on QED radiative corrections to the Casimir force between
two parallel plates is clarified and the low-energy effective field theory for
the Casimir effect in QED is constructed.Comment: 17 pages, revte
Single grain heating due to inelastic cotunneling
We study heating effects of a single metallic quantum dot weakly coupled to
two leads. The dominant mechanism for heating at low temperatures is due to
inelastic electron cotunneling processes. We calculate the grain temperature
profile as a function of grain parameters, bias voltage, and time and show that
for nanoscale size grains the heating effects are pronounced and easily
measurable in experiments.Comment: 4 pages, 3 figures, revtex4, extended and corrected versio
Phonon self-energy corrections to non-zero wavevector phonon modes in single-layer graphene
Phonon self-energy corrections have mostly been studied theoretically and
experimentally for phonon modes with zone-center (q = 0) wave-vectors. Here,
gate-modulated Raman scattering is used to study phonons of a single layer of
graphene (1LG) in the frequency range from 2350 to 2750 cm-1, which shows the
G* and the G'-band features originating from a double-resonant Raman process
with q \not= 0. The observed phonon renormalization effects are different from
what is observed for the zone-center q = 0 case. To explain our experimental
findings, we explored the phonon self-energy for the phonons with non-zero
wave-vectors (q \not= 0) in 1LG in which the frequencies and decay widths are
expected to behave oppositely to the behavior observed in the corresponding
zone-center q = 0 processes. Within this framework, we resolve the
identification of the phonon modes contributing to the G* Raman feature at 2450
cm-1 to include the iTO+LA combination modes with q \not= 0 and the 2iTO
overtone modes with q = 0, showing both to be associated with wave-vectors near
the high symmetry point K in the Brillouin zone
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