54 research outputs found
The Functional Renormalization Group and O(4) scaling
The critical behavior of the chiral quark-meson model is studied within the
Functional Renormalization Group (FRG). We derive the flow equation for the
scale dependent thermodynamic potential at finite temperature and density in
the presence of a symmetry-breaking external field. Within this scheme, the
critical scaling behavior of the order parameter, its transverse and
longitudinal susceptibilities as well as the correlation lengths near the
chiral phase transition are computed. We focus on the scaling properties of
these observables at non-vanishing external field when approaching the critical
point from the symmetric as well as from the broken phase. We confront our
numerical results with the Widom-Griffiths form of the magnetic equation of
state, obtained by a systematic epsilon-expansion of the scaling function. Our
results for the critical exponents are consistent with those recently computed
within Lattice Monte-Carlo studies of the O(4) spin system.Comment: 14 pages, 11 figure
Decoherence effects in Bose-Einstein condensate interferometry. I General Theory
The present paper outlines a basic theoretical treatment of decoherence and
dephasing effects in interferometry based on single component BEC in double
potential wells, where two condensate modes may be involved. Results for both
two mode condensates and the simpler single mode condensate case are presented.
A hybrid phase space distribution functional method is used where the
condensate modes are described via a truncated Wigner representation, and the
basically unoccupied non-condensate modes are described via a positive P
representation. The Hamiltonian for the system is described in terms of quantum
field operators for the condensate and non-condensate modes. The functional
Fokker-Planck equation for the double phase space distribution functional is
derived. Equivalent Ito stochastic equations for the condensate and
non-condensate fields that replace the field operators are obtained, and
stochastic averages of products of these fields give the quantum correlation
functions used to interpret interferometry experiments. The stochastic field
equations are the sum of a deterministic term obtained from the drift vector in
the functional Fokker-Planck equation, and a noise field whose stochastic
properties are determined from the diffusion matrix in the functional
Fokker-Planck equation. The noise field stochastic properties are similar to
those for Gaussian-Markov processes in that the stochastic averages of odd
numbers of noise fields are zero and those for even numbers of noise field
terms are sums of products of stochastic averages associated with pairs of
noise fields. However each pair is represented by an element of the diffusion
matrix rather than products of the noise fields themselves. The treatment
starts from a generalised mean field theory for two condensate mode. The
generalized mean field theory solutions are needed for calculations using the
Ito stochastic field equations.Comment: To be published in Annals of Physics. Full version of paper,
including all Appendices. Journal version only includes Appendix A.
Appendices are in online supplementary material. Cross references to material
in Appendices improved in Version 2 (5 July 2010). Minor amendments made in
Version 3 (23 Nov 2010), including reference to Takagi factorisation of
complex symmetric matrice
Neutrino oscillation studies with IceCube-DeepCore
AbstractIceCube, a gigaton-scale neutrino detector located at the South Pole, was primarily designed to search for astrophysical neutrinos with energies of PeV and higher. This goal has been achieved with the detection of the highest energy neutrinos to date. At the other end of the energy spectrum, the DeepCore extension lowers the energy threshold of the detector to approximately 10 GeV and opens the door for oscillation studies using atmospheric neutrinos. An analysis of the disappearance of these neutrinos has been completed, with the results produced being complementary with dedicated oscillation experiments. Following a review of the detector principle and performance, the method used to make these calculations, as well as the results, is detailed. Finally, the future prospects of IceCube-DeepCore and the next generation of neutrino experiments at the South Pole (IceCube-Gen2, specifically the PINGU sub-detector) are briefly discussed
A muon-track reconstruction exploiting stochastic losses for large-scale Cherenkov detectors
IceCube is a cubic-kilometer Cherenkov telescope operating at the South Pole. The main goal of IceCube is the detection of astrophysical neutrinos and the identification of their sources. High-energy muon neutrinos are observed via the secondary muons produced in charge current interactions with nuclei in the ice. Currently, the best performing muon track directional reconstruction is based on a maximum likelihood method using the arrival time distribution of Cherenkov photons registered by the experiment\u27s photomultipliers. A known systematic shortcoming of the prevailing method is to assume a continuous energy loss along the muon track. However at energies >1 TeV the light yield from muons is dominated by stochastic showers. This paper discusses a generalized ansatz where the expected arrival time distribution is parametrized by a stochastic muon energy loss pattern. This more realistic parametrization of the loss profile leads to an improvement of the muon angular resolution of up to 20% for through-going tracks and up to a factor 2 for starting tracks over existing algorithms. Additionally, the procedure to estimate the directional reconstruction uncertainty has been improved to be more robust against numerical errors
Acute dietary tryptophan depletion impairs maintenance of "affective set" and delayed visual recognition in healthy volunteers
Interrelation between Damage Variables of Continuum Damage Mechanics and Metallographical Parameters in Creep Damage
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