98,794 research outputs found
Rigorous Approach to the Gravitational Lensing
We revisit a weak gravitational lensing problem by constructing a setup which
describes the actual system as accurately as possible and solving the null
geodesic equations. Details are given for the case of a Universe driven only by
a cosmological constant, \Lambda, which confirm the conventional results: The
conventional lensing analysis is correct as it is, without any need for
correction of O(\Lambda). We also treat the cases of the lensing in generic FRW
backgrounds.Comment: 6 pages, the discussion is revise
Genus Topology of the Cosmic Microwave Background from the WMAP 3-Year Data
We have independently measured the genus topology of the temperature
fluctuations in the cosmic microwave background seen in the Wilkinson Microwave
Anisotropy Probe (WMAP) 3-year data. A genus analysis of the WMAP data
indicates consistency with Gaussian random-phase initial conditions, as
predicted by standard inflation. We set 95% confidence limits on
non-linearities of -101 < f_{nl} < 107. We also find that the observed low l (l
<= 8) modes show a slight anti-correlation with the Galactic foreground, but
not exceeding 95% confidence, and that the topology defined by these modes is
consistent with that of a Gaussian random-phase distribution (within 95%
confidence).Comment: MNRAS LaTeX style (mn2e.cls), EPS and JPEG figure
Planetary companions orbiting M giants HD 208527 and HD 220074
Aims. The purpose of the present study is to research the origin of planetary
companions by using a precise radial velocity (RV) survey.
Methods. The high-resolution spectroscopy of the fiber-fed Bohyunsan
Observatory Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy
Observatory (BOAO) is used from September 2008 to June 2012.
Results. We report the detection of two exoplanets in orbit around HD 208527
and HD 220074 exhibiting periodic variations in RV of 875.5 +/- 5.8 and 672.1
+/- 3.7 days. The RV variations are not apparently related to the surface
inhomogeneities and a Keplerian motion of the planetary companion is the most
likely explanation. Assuming possible stellar masses of 1.6 +/- 0.4 and 1.2 +/-
0.3 M_Sun, we obtain the minimum masses for the exoplanets of 9.9 +/- 1.7 and
11.1 +/- 1.8 M_Jup around HD 208527 and HD 220074 with an orbital semi-major
axis of 2.1 +/- 0.2 and 1.6 +/- 0.1 AU and an eccentricity of 0.08 and 0.14,
respectively. We also find that the previously known spectral classification of
HD 208527 and HD 220074 was in error: Our new estimation of stellar parameters
suggest that both HD 208527 and HD 220074 are M giants. Therefore, HD 208527
and HD 220074 are so far the first candidate M giants to harbor a planetary
companion.Comment: 7 pages, 9 figures, 4 tables, accepted for publisation in Astronomy &
Astrophysic
Possible Suppression of Resonant Signals for Split-UED by Mixing at the LHC?
The mixing of the imaginary parts of the transition amplitudes of nearby
resonances via the breakdown of the Breit-Wigner approximation has been shown
to lead to potentially large modifications in the signal rates for new physics
at colliders. In the case of suppression, this effect may be significant enough
to lead to some new physics signatures being initially missed in searches at,
e.g., the LHC. Here we explore the influence of this `width mixing' on the
production of the nearly degenerate, level-2 Kaluza-Klein (KK) neutral gauge
bosons present in Split-UED. We demonstrate that in this particular case large
cross section modifications in the resonance region are necessarily absent and
explain why this is so based on the group theoretical structure of the SM.Comment: 10 pages, 2 figures; discussion and references adde
Isospin-violating dark matter from a double portal
We study a simple model that can give rise to isospin-violating interactions
of Dirac fermion asymmetric dark matter to protons and neutrons through the
interference of a scalar and U(1) gauge boson contribution. The model can
yield a large suppression of the elastic scattering cross section off Xenon
relative to Silicon thus reconciling CDMS-Si and LUX results while being
compatible with LHC findings on the 126 GeV Higgs, electroweak precision tests
and flavour constraints.Comment: 25 pages, 7 figure
Monte Carlo simulations of bosonic reaction-diffusion systems
An efficient Monte Carlo simulation method for bosonic reaction-diffusion
systems which are mainly used in the renormalization group (RG) study is
proposed. Using this method, one dimensional bosonic single species
annihilation model is studied and, in turn, the results are compared with RG
calculations. The numerical data are consistent with RG predictions. As a
second application, a bosonic variant of the pair contact process with
diffusion (PCPD) is simulated and shown to share the critical behavior with the
PCPD. The invariance under the Galilean transformation of this boson model is
also checked and discussion about the invariance in conjunction with other
models are in order.Comment: Publishe
- …