65,006 research outputs found
Thermal Inflation and the Moduli Problem
In supersymmetric theories a field can develop a vacuum expectation value , even though its mass is of order to
. The finite temperature in the early Universe can hold such a
field at zero, corresponding to a false vacuum with energy density . When the temperature falls below , the thermal energy
density becomes negligible and an era of thermal inflation begins. It ends when
the field rolls away from zero at a temperature of order , corresponding to
of order 10 -folds of inflation which does not affect the density
perturbation generated during ordinary inflation. Thermal inflation can solve
the Polonyi/moduli problem if is within one or two orders of magnitude of
.Comment: Revised version to appear in Phys Rev D. Improved discussion of the
possible effect of parametric resonance. Latex, 31 page
Evaluation of the Processing Centers
published or submitted for publicatio
Energy Spectrum of the Electrons Accelerated by a Reconnection Electric Field: Exponential or Power Law?
The direct current (DC) electric field near the reconnection region has been
proposed as an effective mechanism to accelerate protons and electrons in solar
flares. A power-law energy spectrum was generally claimed in the simulations of
electron acceleration by the reconnection electric field. However in most of
the literature, the electric and magnetic fields were chosen independently. In
this paper, we perform test-particle simulations of electron acceleration in a
reconnecting magnetic field, where both the electric and magnetic fields are
adopted from numerical simulations of the MHD equations. It is found that the
accelerated electrons present a truncated power-law energy spectrum with an
exponential tail at high energies, which is analogous to the case of diffusive
shock acceleration. The influences of reconnection parameters on the spectral
feature are also investigated, such as the longitudinal and transverse
components of the magnetic field and the size of the current sheet. It is
suggested that the DC electric field alone might not be able to reproduce the
observed single or double power-law distributions.Comment: 18 pages, 6 figures, published in Ap
Radial Velocities with CRIRES: Pushing precision down to 5-10 m/s
With the advent of high-resolution infrared spectrographs, Radial Velocity
(RV) searches enter into a new domain. As of today, the most important
technical question to address is which wavelength reference is the most
suitable for high-precision RV measurements.
In this work we explore the usage of atmospheric absorption features. We make
use of CRIRES data on two programs and three different targets. We re-analyze
the data of the TW Hya campaign, reaching a dispersion of about 6 m/s on the RV
standard in a time scale of roughly 1 week. We confirm the presence of a
low-amplitude RV signal on TW Hya itself, roughly 3 times smaller than the one
reported at visible wavelengths. We present RV measurements of Gl 86 as well,
showing that our approach is capable of detecting the signal induced by a
planet and correctly quantifying it.
Our data show that CRIRES is capable of reaching a RV precision of less than
10 m/s in a time-scale of one week. The limitations of this particular approach
are discussed, and the limiting factors on RV precision in the IR in a general
way. The implications of this work on the design of future dedicated IR
spectrographs are addressed as well.Comment: 9 pages, accepted for publication in A&
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