Browsing by Author "Theodorakis, Stavros"
Now showing items 1-20 of 43
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Analytic Q ball solutions in a parabolic-type potential
Theodorakis, Stavros (2000)We introduce a piecewise parabolic potential for a complex scalar field and we show that it admits stable Q ball solutions. These solutions can be found analytically, unlike the case of polynomial potentials. We find stable ...
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Analytic solutions for the evolution of domain walls
Theodorakis, Stavros (1999)We introduce an unusual asymmetric double well potential, a piecewise parabolic one, and we show that the solutions for the evolution of its domain walls can be found analytically, in contrast with the case of the standard ...
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Analytic vortex solutions in an unusual Mexican-hat potential
Theodorakis, Stavros (1997)We introduce an unusual Mexican-hat potential, a piecewise parabolic one, and we show that its vortex solutions can be found analytically, in contrast to the case of the standard |Ψ|4 field theory.
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Bound states in a nonlinear Kronig-Penney model
Theodorakis, Stavros; Leontidis, Epameinondas (1997)We study the bound states of a Kronig Penney potential for a nonlinear one-dimensional Schrödinger equation. This potential consists of a large, but not necessarily infinite, number of equidistant δ-function wells. We show ...
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Bound states in a nonlinear Kronig-Penney model
Theodorakis, Stavros; Leontidis, Epameinondas (1997)We study the bound states of a Kronig Penney potential for a nonlinear one-dimensional Schrödinger equation. This potential consists of a large, but not necessarily infinite, number of equidistant δ-function wells. We show ...
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Certain similarities between the evolution of cooperation and phase transitions in physics
Theodorakis, Stavros (2001)The theory of evolution of cooperation presents a number of striking similarities to the theory of phase transitions in physics. A system that is in a higher energy phase P+ will make a transition to a lower energy phase ...
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Comment on "vortices with ferromagnetic superfluid core in He3-B"
Fetter, A. L.; Theodorakis, Stavros (1984)
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Emulation of the evolution of a Bose-Einstein condensate in a time-dependent harmonic trap
Theodorakis, Stavros; Constantinou, Y. (2007)We emulate the ground state of a Bose-Einstein condensate in a time-dependent isotropic harmonic trap by constructing analytic simulacra of a transformed wavefunction in the regions around the origin and far from the origin. ...
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Evolution of a Bose-Einstein condensate in a rapidly expanding circular box
Theodorakis, Stavros; Constantinou, Y. (2007)We examine the evolution of the ground state of a Bose-Einstein condensate in a two-dimensional circular box, the wall of which is initially at rest and then recedes with large and constant speed. The final state of the ...
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Field-independent anisotropy in layered superconductors
Theodorakis, Stavros; Feinberg, D. (1992)Multilayered superconducting SW structures with inequivalent layers are considered, where superconductivity in W (weakly superconducting) layers is induced through their proximity with the S (strongly superconducting) ...
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Fronts in a piecewise linear Schrödinger equation
Theodorakis, Stavros (2002)We examine the conditions that are necessary for the appearance of fronts as solutions of nonlinear Schrödinger-like equations. We show that fronts can appear even when the potential in these equations has only one minimum. ...
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Ginzburg-Landau modelisation of superconducting multilayers with proximity effect
Ettouhami, A. M.; Feinberg, D.; Theodorakis, Stavros (1994)A phenomenological modelisation of superlattices made of alternating superconducting (S) and normal (N) layers coupled by proximity effect is presented. It is shown that the anisotropy of such superconductors is not a ...
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Heavy family masses: Analytic results
Dimopoulos, Savas; Theodorakis, Stavros (1985)We solve analytically the one-loop renormalization group equations for the fermion mass matrices and the quartic coupling, assuming a perturbative SU(3)×SU(2)×U(1) desert, one elementary Higgs boson and any number of ...
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Hierarchy of Tc's in the thallium high-Tc superconductors
Theodorakis, Stavros (1988)We present a phenomenological formalism determining the critical temperatures of the various superconducting phases in the newly discovered thallium high-Tc superconductors. Tc cannot exceed 146 K (164 K) for the compounds ...
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Inequivalent layers can cause flux-lattice melting in layered superconductors
Theodorakis, Stavros (1990)The high-Tc superconductors consist typically of superconducting (S) and nonsuperconducting (W) layers. The latter layers acquire actually a nonzero order parameter through a proximity effect. We show that the vortices ...
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Inequivalent layers in the phenomenology of high Tc superconductors
Theodorakis, Stavros; Tešanović, Z. (1988)We present a phenomenological model describing the high Tc superconductors. The model accounts for the observed positive curvature in the temperature dependence of the H⊥ c2, in terms of a proximity effect between the ...
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Lagrangian of superfluid He3
Theodorakis, Stavros (1988)This paper presents a phenomenological Lagrangian that fully describes the dynamics of any homogeneous phase of superfluid He3, unitary or not, omitting relaxation. This Lagrangian is built by using the concept of a local ...
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Local pinning of trial wave functions: An optimization method without integrals for finding approximate solutions of field equations
Theodorakis, Stavros; Kindyni, N. (2010)We present an optimization method that requires no integrations for obtaining approximate solutions of field equations of the form F(Ψ(r{combining right arrow above}))=0. The expression F(Ψ(r{combining right arrow above})) ...
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Lopsided vortex cells in rotating Bose-Einstein condensates
Theodorakis, Stavros (2015)The amplitude |Ψ| of the wavefunction of a repulsive Bose-Einstein condensate in a two-dimensional axisymmetric harmonic trap decreases as we go from the center of the condensate towards its edge. Consequently the wavefunction ...
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Magnetic-field inversion in vortices in multilayers
Theodorakis, Stavros; Leontidis, Epameinondas (1997)We present a description of very dense vortex lattices in highly anisotropic multilayers, for high fields parallel to the layers. We show that a magnetic-field inversion can occur away from the center of a vortex, provided ...