32,212 research outputs found
A Time Evolution Study of the Superhumps of the Dwarf Nova 1RXS J232953.9+062814 by Wavelet Transform
The time evolution behaviour of the superhumps of the dwarf nova 1RXS
J232953.9+062814 is investigated with the wavelet analysis method. On the basis
of two nights CCD photometry performed during its first superoutburst as well
as other published brightness data, we reveal the superhump's time-dependence
as a function of periods and time. Our light curves, which phased in the rapid
decay ending portion of the superoutburst and in the dawn of a following normal
outburst, are important to help trace the superhump evolution for the star.
Evident amplitude variations of the superhumps, reflecting the fading of
outbursts, are detected. The general profile of brightness fading over the
outbursts roughly followed an exponential decay law or a form of a five-order
polynomial. Both the superhump period and the orbital period of the binary
system are detected in the present data. We obtain P_sh=0.04575(5) d and
P_orb=0.04496(5) d. They agree with the existing values based on additional
data. The two periods exchanged their roles during the superhump evolution.Comment: 7 pages, 9 figures, submitted to Astronomy & Astrophysic
Upsilon Transverse Momentum at Hadron Colliders
We predict the shape of the transverse momentum p_T spectrum of Upsilon
production. The distribution at low p_T is dominated by the region of small
impact parameter b and may be computed reliably in perturbation theory. We
resum to all orders in the strong coupling alpha_s the process-independent
large logarithmic contributions that arise from initial-state gluon showers in
the small p_T (< M_Upsilon) region. The cross section at large p_T is
represented by the alpha_s^3 lowest-order non-vanishing perturbative
contribution.Comment: 4 pages, 5 figures. Presented at the 2004 Meeting of the APS Division
of Particles and Fields, University of California, Riverside, CA, Aug 26-31,
200
Breakdown of Conventional Factorization for Isolated Photon Cross Sections
Using as an example, we show that the
conventional factorization theorem in perturbative quantum chromodynamics
breaks down for isolated photon cross sections in a well defined part of phase
space. Implications and physical consequences are discussed.Comment: 11 pages, RevTex, 1 figure in postscrip
On fast radial propagation of parametrically excited geodesic acoustic mode
The spatial and temporal evolution of parametrically excited geodesic
acoustic mode (GAM) initial pulse is investigated both analytically and
numerically. Our results show that the nonlinearly excited GAM propagates at a
group velocity which is, typically, much larger than that due to finite ion
Larmor radius as predicted by the linear theory. The nonlinear dispersion
relation of GAM driven by a finite amplitude drift wave pump is also derived,
showing a nonlinear frequency increment of GAM. Further implications of these
findings for interpreting experimental observations are also discussed
Modular Equations and Distortion Functions
Modular equations occur in number theory, but it is less known that such
equations also occur in the study of deformation properties of quasiconformal
mappings. The authors study two important plane quasiconformal distortion
functions, obtaining monotonicity and convexity properties, and finding sharp
bounds for them. Applications are provided that relate to the quasiconformal
Schwarz Lemma and to Schottky's Theorem. These results also yield new bounds
for singular values of complete elliptic integrals.Comment: 23 page
Dimensional Regularization and Dimensional Reduction in the Light Cone
We calculate all the 2 to 2 scattering process in Yang-Mills theory in the
Light Cone gauge, with the dimensional regulator as the UV regulator. The IR is
regulated with a cutoff in . It supplements our earlier work, where a
Lorentz non-covariant regulator was used and the final results bear some
problems in gauge fixing. Supersymmetry relations among various amplitudes are
checked using the light cone superfields.Comment: current version accepted by PR
Dynamical properties of a trapped dipolar Fermi gas at finite temperature
We investigate the dynamical properties of a trapped finite-temperature
normal Fermi gas with dipole-dipole interaction. For the free expansion
dynamics, we show that the expanded gas always becomes stretched along the
direction of the dipole moment. In addition, we present the temperature and
interaction dependences of the asymptotical aspect ratio. We further study the
collapse dynamics of the system by suddenly increasing the dipolar interaction
strength. We show that, in contrast to the anisotropic collapse of a dipolar
Bose-Einstein condensate, a dipolar Fermi gas always collapses isotropically
when the system becomes globally unstable. We also explore the interaction and
temperature dependences for the frequencies of the low-lying collective
excitations.Comment: 11 pages, 7 figure
Effects of energetic particles on zonal flow generation by toroidal Alfven eigenmode
Generation of zonal ow (ZF) by energetic particle (EP) driven toroidal Alfven
eigenmode (TAE) is investigated using nonlinear gyrokinetic theory. It is found
that, nonlinear resonant EP contri- bution dominates over the usual Reynolds
and Maxwell stresses due to thermal plasma nonlinear response. ZF can be forced
driven in the linear growth stage of TAE, with the growth rate being twice the
TAE growth rate. The ZF generation mechanism is shown to be related to
polarization induced by resonant EP nonlinearity. The generated ZF has both the
usual meso-scale and micro- scale radial structures. Possible consequences of
this forced driven ZF on the nonlinear dynamics of TAE are also discussed.Comment: To be submitted to Physics of Plasma
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