31,870 research outputs found

    Symmetry and anti-symmetry of the CMB anisotropy pattern

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    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

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    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

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    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

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    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

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    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

    Application of Dimethyl Ether in Compression Ignition Engines

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    De sidste dages heldige:om krimifiktion og Gunnar Staalesens forfatterskab

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