31,870 research outputs found
Symmetry and anti-symmetry of the CMB anisotropy pattern
Given an arbitrary function, we may construct symmetric and antisymmetric
functions under a certain operation. Since statistical isotropy and homogeneity
of our Universe has been a fundamental assumption of modern cosmology, we do
not expect any particular symmetry or antisymmetry in our Universe. Besides
fundamental properties of our Universe, we may also figure our contamination
and improve the quality of the CMB data products, by matching the unusual
symmetries and antisymmetries of the CMB data with known contaminantions.
Noting this, we have investigated the symmetry and antisymmetry of CMB
anisotropy pattern, which provides the deepest survey. If we let the operation
to be a coordinate inversion, the symmetric and antisymmetric functions have
even and odd-parity respectively. The investigation on the parity of the recent
CMB data shows a large-scale odd-parity preference, which is very unlikely in
the statistical isotropic and homogeneous Universe. We have investigated the
association of the WMAP systematics with the anomaly, but not found a definite
non-cosmological cause. Additionally, we have investigated the phase of even
and odd multipole data respectively, and found the behavior distinct from each
other. Noting the odd-parity preference anomaly, we have fitted a cosmological
model respectively to even and odd multipole data, and found significant
parametric tension. Besides anomalies explicitly associated with parity, there
are anomalous lack of large-scale correlation in CMB data. Noting the
equivalence between the power spectrum and the correlation, we have
investigated the association between the lack of large-angle correlation and
the odd-parity preference of the angular power spectrum. From our analysis, we
find that the odd-parity preference at low multipoles is, in fact,
phenomenologically identical with the lack of large-angle correlation.Comment: review articl
A Model for the Thermodynamics of Globular Proteins
Comments: 6 pages RevTeX, 6 Postscript figures. We review a statistical
mechanics treatment of the stability of globular proteins based on a simple
model Hamiltonian taking into account protein self interactions and
protein-water interactions. The model contains both hot and cold folding
transitions. In addition it predicts a critical point at a given temperature
and chemical potential of the surrounding water. The universality class of this
critical point is new
Statistical mechanics of warm and cold unfolding in proteins
We present a statistical mechanics treatment of the stability of globular
proteins which takes explicitly into account the coupling between the protein
and water degrees of freedom. This allows us to describe both the cold and the
warm unfolding, thus qualitatively reproducing the known thermodynamics of
proteins.Comment: 5 pages, REVTex, 4 Postscript figure
Moving Multi-Channel Systems in a Finite Volume with Application to Proton-Proton Fusion
The spectrum of a system with multiple channels composed of two hadrons with
nonzero total momentum is determined in a finite cubic volume with periodic
boundary conditions using effective field theory methods. The results presented
are accurate up to exponentially suppressed corrections in the volume due to
the finite range of hadronic interactions. The formalism allows one to
determine the phase shifts and mixing parameters of pipi-KK isosinglet coupled
channels directly from Lattice Quantum Chromodynamics. We show that the
extension to more than two channels is straightforward and present the result
for three channels. From the energy quantization condition, the volume
dependence of electroweak matrix elements of two-hadron processes is extracted.
In the non-relativistic case, we pay close attention to processes that mix the
1S0-3S1 two-nucleon states, e.g. proton-proton fusion (pp -> d+ e^+ + nu_e),
and show how to determine the transition amplitude of such processes directly
from lattice QCD.Comment: 20 pages, 3 figure
Simulation of waviness in neutron guides
As the trend of neutron guide designs points towards longer and more complex
guides, imperfections such as waviness becomes increasingly important.
Simulations of guide waviness has so far been limited by a lack of reasonable
waviness models. We here present a stochastic description of waviness and its
implementation in the McStas simulation package. The effect of this new
implementation is compared to the guide simulations without waviness and the
simple, yet unphysical, waviness model implemented in McStas 1.12c and 2.0
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