BCS-BEC crossover in a gas of Fermi atoms with a p-wave Feshbach resonance

We investigate unconventional superfluidity in a gas of Fermi atoms with an anisotropic p-wave Feshbach resonance. Including the p-wave Feshbach resonance as well as the associated three kinds of quasi-molecules with finite orbital angular momenta $L_z=\pm1,0$, we calculate the transition temperature of the superfluid phase. As one passes through the p-wave Feshbach resonance, we find the usual BCS-BEC crossover phenomenon. The p-wave BCS state continuously changes into the BEC of bound molecules with L=1. Our calculation includes the effect of fluctuations associated with Cooper-pairs and molecules which are not Bose-condensed.Comment: 9 pages, 3 figures, 1 tabl

The ground state in a spin-one color superconductor

Color superconductors in which quarks of the same flavor form Cooper pairs are investigated. These Cooper pairs carry total spin one. A systematic group-theoretical classification of possible phases in a spin-one color superconductor is presented, revealing parallels and differences to the theory of superfluid $^3$He. General expressions for the gap parameter, the critical temperature, and the pressure are derived and evaluated for several spin-one phases, with special emphasis on the angular structure of the gap equation. It is shown that the (transverse) color-spin-locked phase is expected to be the ground state.Comment: 36 pages, 3 figures, error corrected in App. C, conclusion change

Development of the inner tracker detector electronics for LHCb

This paper describes the development and testing of the Inner Tracker detector modules including the silicon sensors and the electronic readout hybrid with the Beetle frontend chip. Testbeam measurements on the sensor performance including signal-to-noise and efficiency are discussed. We also present preformance studies on the digital optical transmission line. Talk presented at 8th workshop on Electronics for LHCb Experiments, Colmar, September 9-13, 200

Fate of the inert three-flavor, spin-zero color-superconducting phases

I investigate some of the inert phases in three-flavor, spin-zero color-superconducting quark matter: the CFL phase (the analogue of the B phase in superfluid $^3\rm He$), the A and A* phases, and the 2SC and sSC phases. I compute the pressure of these phases with and without the neutrality condition. It is shown that the 2SC phase is identical to the A* phase up to a color rotation. The CFL phase is the energetically favored phase except for a small region of intermediate densities where the 2SC/A* phase is favored.Comment: 9 pages, 1 figure; the version accepted to publish in PR

Causality vs. Ward identity in disordered electron systems

We address the problem of fulfilling consistency conditions in solutions for disordered noninteracting electrons. We prove that if we assume the existence of the diffusion pole in an electron-hole symmetric theory we cannot achieve a solution with a causal self-energy that would fully fit the Ward identity. Since the self-energy must be causal, we conclude that the Ward identity is partly violated in the diffusive transport regime of disordered electrons. We explain this violation in physical terms and discuss its consequences.Comment: 4 pages, REVTeX, 6 EPS figure

Spontaneous spin textures in dipolar spinor condensates

We have mapped out a detailed phase diagram that shows the ground state structure of a spin-1 condensate with magnetic dipole-dipole interactions. We show that the interplay between the dipolar and the spin-exchange interactions induces a rich variety of quantum phases that exhibit spontaneous magnetic ordering in the form of intricate spin textures.Comment: 4.1 pages, 4 figure

The LHCb Silicon Tracker: lessons learned (so far)

The LHCb Silicon Tracker is part of the main tracking system of the LHCb detector. It covers the full acceptance angle in front of the dipole magnet in the Tracker Turicensis (TT) station and the innermost part in the three Inner Tracker (IT) stations downstream of the magnet. We report on final elements of the production, the installation and commissioning process in the experiment. Focusing on electronic and hardware issues we describe the lessons learned and the pitfalls encountered. First experience of detector operation is presented

Theoretical description of mixed film formation at the air/water interface : carboxylic acids–fatty amines

Thermodynamic parameters of mixed monolayer formation of aliphatic amines CnH2n+1NH2 and carboxylic acids CnH2n+1COOH (n = 6–16) are calculated using the quantum chemical semiempirical PM3 method. Four types of mixed dimers and tetramers amine–acid are considered. The total contribution of interactions between the hydrophilic parts of amine and acid into clusterization Gibbs energy is slightly lower than the corresponding interactions for individual surfactants. It suggests a synergetic interaction between the regarded amphiphilic compounds as proved by experimental data in the literature. Two types of competitive film formation are possible: mixed 2D film 1, where the molecules of the minor component are single distributed among the molecules of the prevailing second component (mixture of components on molecular level), and 2D film 2 with a domain structure comprised of pure component “islands” linked together. The dependence of the Gibbs energy of clusterization per monomer for 2D film 1 on the component mole fraction shows that the maximum synergetic effect is typical for the case that both surfactants have the same even number of carbon atoms in the hydrocarbon chain and form an equimolar mixture. Formation of 2D film 1 is more preferable than that of 2D film 2, if the difference of the hydrocarbon chain lengths is not larger than 5 methylene units. The limiting mole fraction of carboxylic acids in such mixed monolayers is 66.7%

Two-fluid model for a rotating trapped Fermi gas in the BCS phase

We investigate the dynamical properties of a superfluid gas of trapped fermionic atoms in the BCS phase. As a simple example we consider the reaction of the gas to a slow rotation of the trap. It is shown that the currents generated by the rotation can be understood within a two-fluid model similar to the one used in the theory of superconductors, but with a position dependent ratio of normal and superfluid densities. The rather general result of this paper is that already at very low temperatures, far below the critical one, an important normal-fluid component appears in the outer regions of the gas. This renders the experimental observation of superfluidity effects more difficult and indicates that reliable theoretical predictions concerning other dynamical properties, like the frequencies of collective modes, can only be made by taking into account temperature effects.Comment: 6 pages, 4 figure

Scaling behavior of the momentum distribution of a quantum Coulomb system in a confining potential

We calculate the single-particle momentum distribution of a quantum many-particle system in the presence of the Coulomb interaction and a confining potential. The region of intermediate momenta, where the confining potential dominates, marks a crossover from a Gaussian distribution valid at low momenta to a power-law behavior valid at high momenta. We show that for all momenta the momentum distribution can be parametrized by a $q$-Gaussian distribution whose parameters are specified by the confining potential. Furthermore, we find that the functional form of the probability of transitions between the confined ground state and the $n^{th}$ excited state is invariant under scaling of the ratio $Q^2/\nu_n$, where $Q$ is the transferred momentum and $\nu_n$ is the corresponding excitation energy. Using the scaling variable $Q^2/\nu_n$ the maxima of the transition probabilities can also be expressed in terms of a $q$-Gaussian.Comment: 6 pages, 5 figure