Integrability of the Russian doll BCS model

We show that integrability of the BCS model extends beyond Richardson's model (where all Cooper pair scatterings have equal coupling) to that of the Russian doll BCS model for which the couplings have a particular phase dependence that breaks time-reversal symmetry. This model is shown to be integrable using the quantum inverse scattering method, and the exact solution is obtained by means of the algebraic Bethe ansatz. The inverse problem of expressing local operators in terms of the global operators of the monodromy matrix is solved. This result is used to find a determinant formulation of a correlation function for fluctuations in the Cooper pair occupation numbers. These results are used to undertake exact numerical analysis for small systems at half-filling.

Superconducting Correlations in Metallic Nanoparticles: Exact Solution of the BCS Model by the Algebraic Bethe Ansatz

Superconducting pairing of electrons in nanoscale metallic particles with discrete energy levels and a fixed number of electrons is described by the reduced Bardeen, Cooper, and Schrieffer model Hamiltonian. We show that this model is integrable by the algebraic Bethe ansatz. The eigenstates, spectrum, conserved operators, integrals of motion, and norms of wave functions are obtained. Furthermore, the quantum inverse problem is solved, meaning that form factors and correlation functions can be explicitly evaluated. Closed form expressions are given for the form factors and correlation functions that describe superconducting pairing.

Ground-State Entanglement of the BCS Model

The concept of local concurrence is used to quantify the entanglement between a single qubit and the remainder of a multiqubit system. For the ground state of the BCS model in the thermodynamic limit the set of local concurrences completely describes the entanglement. As a measure for the entanglement of the full system we investigate the average local concurrence (ALC). We find that the ALC satisfies a simple relation with the order parameter. We then show that for finite systems with a fixed particle number, a relation between the ALC and the condensation energy exposes a threshold coupling. Below the threshold, entanglement measures besides the ALC are significant.

Integrable coupling in a model for Josephson tunneling between non-identical BCS systems

We extend a recent construction for an integrable model describing Josephson tunneling between identical BCS systems to the case where the BCS systems have different single particle energy levels. The exact solution of this generalized model is obtained through the Bethe ansatz.

Integrability and exact solution for coupled BCS systems associated with the su(4) Lie algebra

We introduce an integrable model for two coupled BCS systems through a solution of the Yang-Baxter equation associated with the Lie algebra su(4). By employing the algebraic Bethe ansatz, we determine the exact solution for the energy spectrum. An asymptotic analysis is conducted to determine the leading terms in the ground state energy, the gap and some one point correlation functions at zero temperature. (C) 2002 Published by Elsevier Science B.V.

BCS-mittariston ja strategisten tavoitteiden viestintä taloushallinnon palvelukeskuksessa

Organisaation strategia ja visio jäävät työntekijöille usein kaukaisiksi ja vieraiksi asioiksi. Strategian toimeenpanon kannalta on oleellista, että tavoitteet ja toimintasuunnitelmat viestitään koko organisaatiolle. Sen vuoksi tämän tutkimuksen tavoitteena on laatia suunnitelma taloushallinnon palvelukeskuksen BSC-mittariston ja strategisten tavoitteiden viestimisestä. Henkilöstön tulee nähdä niiden yhteys omaan työhön. Tätä kautta jokainen voi vaikuttaa tavoitteiden toteutumiseen. Ta-voitteiden sisäistäminen lisää myös työtyytyväisyyttä. Tutkimus perustuu strategiaviestinnän ja Balanced scorecardin teoriaan. Empiiristä osuutta varten BSC-mittariston rakennetta ja tarkoitusta on selvitetty haastattelemalla palvelukeskuksen päällikköä. Haastattelumenetelminä on käytetty avointa haastattelua ja puolistrukturoitua haastattelua. Viestintäsuunnitelmassa viestintä tapahtuu avoimen keskustelun sekä tiimi- ja yksilökohtaisten mittaristojen avulla. Intranetiä ja ilmoitustauluja käytetään lisätiedon jakamiseen sekä palautteen keräämiseen. Työtyytyväisyyttä ja motivaatiota pa-rannetaan oman työn merkityksen ymmärtämisen kautta. Esimiehille tarjotaan tarpeen mukaan viestintään ja mittariston rakentamiseen liittyvää koulutusta.

Taxonomía, abundancia estacional, edad y crecimiento y biología reproductiva de Narcine entemedor Jordan y Starks (Chondrichthyes; Narcinidae), en Bahía Almejas, BCS., México

Tesis (Doctorado en Ciencias con Especialidad en Ecología Acuática y Pesca) UANL

COMP1205 LEPP: BCS Code of Conduct

Notes, slides, links

Pareamento BCS em um Líquido de Luttinger em 1D

In this work we investigate the effect of a BCS-type pairing term for free spinless fermions, with a propensity to form a condensate of pairs in a 1+1 dimension. Using the of bosonization technique we explore the possible condition of existence of quasiparticles in a superconducting state. Although there is no spontaneous breaking of chiral symmetry the propagator of one-particle fermion is massive and, in fact, resembles the one-particle Green s function of conventional quasiparticles

BCS superconductivity in the van Hove scenario in s and d waves

The effect of including a van Hove singularity in the density of state of a renormalized BCS equation in s and d waves and its appropriateness in describing some properties of high-Tc cuprates in the weak-coupling region are studied in two space dimensions. The specific heat and knight shift as a function of temperature exhibit scaling below the critical temperature in d wave. We also study the jump in the specific heat at the critical temperature Tc in s and d waves, which can have values significantly higher than the standard BCS values and which increases with Tc, as experimentally observed in many d-wave high-Tc materials. The experimental results on the specific heat and knight shift of the Y-123 system are compared with the theoretical predictions.

Universal scaling in a trapped Fermi super-fluid in the BCS-unitarity crossover

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

BCS-BEC crossover in a trapped Fermi super-fluid using a density-functional equation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Universal behavior of a trapped Fermi superfluid in the BCS-unitarity crossover

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nonlinear Schrodinger equation for a superfluid Fermi gas in the BCS-BEC crossover

We introduce a quasianalytic nonlinear Schrodinger equation with beyond mean-field corrections to describe the dynamics of a zero-temperature dilute superfluid Fermi gas in the crossover from the weak-coupling Bardeen-Cooper-Schrieffer (BCS) regime, where k(F)parallel to a parallel to << 1 with a the s-wave scattering length and k(F) the Fermi momentum, through the unitarity limit k(F)a ->+/-infinity to the Bose-Einstein condensation (BEC) regime where k(F)a > 0. The energy of our model is parametrized using the known asymptotic behavior in the BCS, BEC, and the unitarity limits and is in excellent agreement with accurate Green's-function Monte Carlo calculations. The model generates good results for frequencies of collective breathing oscillations of a trapped Fermi superfluid.