3,712 research outputs found
The Cabibbo-Kobayashi-Maskawa density matrices
The flavor changing charged currents of the weak sector of the Standard Model
are studied in the framework of a quantum statistical approach. The quantum
superposition of same-type quarks, generated by the Cabibbo-Kobayashi-Maskawa
matrix, is used to define three density matrices, one for each quark family.
The properties of such density matrices are analyzed, in particular, the
associated von Neumann entropy. It is proven that, due to the unitarity of the
Cabibbo-Kobayashi-Maskawa matrix, the quantum mixtures of quarks resulting from
the weak interaction do not increase entropy and, therefore, the violation of
CP and T symmetries cannot be related to the second law of thermodynamics.Comment: 3 page
Tricritical Point in Quantum Phase Transitions of the Coleman-Weinberg Model at Higgs Mass
The tricritical point, which separates first and second order phase
transitions in three-dimensional superconductors, is studied in the
four-dimensional Coleman-Weinberg model, and the similarities as well as the
differences with respect to the three-dimensional result are exhibited. The
position of the tricritical point in the Coleman-Weinberg model is derived and
found to be in agreement with the Thomas-Fermi approximation in the
three-dimensional Ginzburg-Landau theory. From this we deduce a special role of
the tricritical point for the Standard Model Higgs sector in the scope of the
latest experimental results, which suggests the unexpected relevance of
tricritical behavior in the electroweak interactions.Comment: 5 pages, 1 figure, published in Phys. Lett.
Phenomenological correlations in high-temperature superconductors
An interpretation of the quadratic parameter of the Ginzburg-Landau theory of
superconductivity is presented in this paper. The negative term in the
potential, which allows the spontaneous symmetry breaking, is interpreted as a
direct contribution from the energy gap at the Fermi surface to the effective
potential. As a result, in the London approximation of the Ginzburg-Landau
theory for type-II superconductors, a strong correlation is predicted and
observed between the upper critical field at zero kelvin and the critical
temperature in high temperature superconductors.Comment: 4 pages, 2 figure
Metallic slabs: Perturbative treatments based on jellium
We examine first-order perturbative results based on jellium for the surface
energy of slabs of simple metals, using various local pseudopotentials
(Ashcroft, Heine-Abarenkov and evanescent core). The difference between the
pseudopotential and the jellium potential is averaged along the plane parallel
to the surface. We compare these perturbative results with those of the
stabilized jellium model (a modification of the regular jellium model in which
the perturbation appears in the energy functional right from the outset) and
with the output of other perturbative and non-perturbative calculations.Comment: 15 pages, 2 figures, to appear in Prog. Surf. Sc
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