Results 1 - 10 of 5978
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[en] The authors consider a model of superconducting pairing with a gap function that is odd in k-kF. In this case superconductivity is possible even in the presence of arbitrarily strong point repulsion between electrons, which is an attractive feature from the viewpoint of the theory of high-Tc metal oxides. The authors suggest a model of pairing interaction in which the equations of the BCS theory can be solved exactly, which makes it possible to fully analyze the ranges of existence of ordinary (open-quotes evenclose quotes) and open-quotes oddclose quotes pairing in terms of the interaction parameters. The authors show that normal impurities (disorder) lead to extremely strong suppression of open-quotes oddclose quotes pairing, even stronger than magnetic impurities do in conventional superconductors
[en] We present the first study of pairing in nuclei including three-nucleon forces. We perform systematic calculations of the odd-even mass staggering generated using a microscopic pairing interaction at first order in chiral low-momentum interactions. Significant repulsive contributions from the leading chiral three-nucleon forces are found. Two- and three-nucleon interactions combined account for approximately 70% of the experimental pairing gaps, which leaves room for self-energy and induced interaction effects that are expected to be overall attractive in nuclei.
[en] We study trace formulas for the exponentials of general fermion bilinears, including pairing terms and including non-Hermitian forms. In particular, we give elementary derivations for determinant and Pfaffian formulae for such traces and use these to obtain general expressions for the full counting statistics in states associated with quadratic Hamiltonians, including BCS-like pairing terms and fermion parity in a prescribed region or set of modes. We also derive Pfaffian expressions for state overlaps and counting statistics in states built out of the vacuum by creation of pairs of particles. (paper)
[en] This is a partly non-technical introduction to selected topics on tensor network methods, based on several lectures and introductory seminars given on the subject. It should be a good place for newcomers to get familiarized with some of the key ideas in the field, specially regarding the numerics. After a very general introduction we motivate the concept of tensor network and provide several examples. We then move on to explain some basics about Matrix Product States (MPS) and Projected Entangled Pair States (PEPS). Selected details on some of the associated numerical methods for 1d and 2d quantum lattice systems are also discussed. - Highlights: • A practical introduction to selected aspects of tensor network methods is presented. • We provide analytical examples of MPS and 2d PEPS. • We provide basic aspects on several numerical methods for MPS and 2d PEPS. • We discuss a number of applications of tensor network methods from a broad perspective
[en] In the years 1964-66 several physicists from several groups were searching quite independently for new symmetries related to the proton-neutron pairing interaction. They exploited the so-called quasi-spin method introduced earlier to apply to the system of electrons and then to identical nucleons (only protons or only neutrons). In what follows, a short introduction to the quasi-spin method is presented and then its application to the pairing interaction of neutrons (protons) is given. With the help of the quasi-spin method, the orthogonal symmetry groups SO(5) and SO(8) are shown to deal with proton-neutron pairing interaction in j - j and L - S coupling schemes, respectively. Comments about chronology of published papers related to the symmetry of pairing interaction written by inventors of the new symmetries are also made. (author)
[en] We propose a simple criterion for revealing the breaking of pair interaction symmetry in strongly coupled dissipative systems. The criterion is based on the analysis of correlations between the velocities of strongly interacting particles, which can be measured relatively easily in experiments with macroparticles in various media. We derive analytic relations that make it possible to calculate the derivatives of the interaction force between a pair of particles from the data on the correlations of their velocities and coordinates. The proposed criterion and relations are verified using the results of numerical simulation of the dynamics of dust particles in a plasma.
[en] The Gutzwiller approach to the repulsive Hubbard model is extended to the negative-U case. The repulsion-attraction transformation of the Hamiltonian is shown to be valid also for this particular mean field approximation. The physical meaning of the results is discussed. (Author)