5,823 research outputs found
Thermodynamic identities and particle number fluctuations in weakly interacting Bose--Einstein condensates
We derive exact thermodynamic identities relating the average number of
condensed atoms and the root-mean-square fluctuations determined in different
statistical ensembles for the weakly interacting Bose gas confined in a box.
This is achieved by introducing the concept of {\it auxiliary partition
functions} for model Hamiltonians that do conserve the total number of
particles. Exploiting such thermodynamic identities, we provide the first,
completely analytical prediction of the microcanonical particle number
fluctuations in the weakly interacting Bose gas. Such fluctuations, as a
function of the volume V of the box are found to behave normally, at variance
with the anomalous scaling behavior V^{4/3} of the fluctuations in the ideal
Bose gas.Comment: 5 pages, 1 figur
Condensate statistics in interacting Bose gases: exact results
Recently, a Quantum Monte Carlo method alternative to the Path Integral Monte
Carlo method was developed for the numerical solution of the N-boson problem;
it is based on the stochastic evolution of classical fields. Here we apply it
to obtain exact results for the occupation statistics of the condensate mode in
a weakly interacting trapped one-dimensional Bose gas. The temperature is
varied across the critical region down to temperatures lower than the trap
level spacing. We verify that the number-conserving Bogoliubov theory gives
accurate predictions provided that the non-condensed fraction is small.Comment: 4 pages, 3 figures; typo corrected in eq.5; references adde
Quantized Roentgen Effect in Bose-Einstein Condensates
A classical dielectric moving in a charged capacitor can create a magnetic
field (Roentgen effect). A quantum dielectric, however, will not produce a
magnetization, except at vortices. The magnetic field outside the quantum
dielectric appears as the field of quantized monopoles
Alternative translation initiation in rat brain yields K2P2.1 potassium channels permeable to sodium.
K(2P) channels mediate potassium background currents essential to central nervous system function, controlling excitability by stabilizing membrane potential below firing threshold and expediting repolarization. Here, we show that alternative translation initiation (ATI) regulates function of K(2P)2.1 (TREK-1) via an unexpected strategy. Full-length K(2P)2.1 and an isoform lacking the first 56 residues of the intracellular N terminus (K(2P)2.1Delta1-56) are produced differentially in a regional and developmental manner in the rat central nervous system, the latter passing sodium under physiological conditions leading to membrane depolarization. Control of ion selectivity via ATI is proposed to be a natural, epigenetic mechanism for spatial and temporal regulation of neuronal excitability
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