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Krefl D.,Center for Theoretical Physics
Journal of High Energy Physics | Year: 2014

The β-ensemble with cubic potential can be used to study a quantum particle in a double-well potential with symmetry breaking term. The quantum mechanical perturbative energy arises from the ensemble free energy in a novel large N limit. A relation between the generating functions of the exact non-perturbative energy, similar in spirit to the one of Dunne-Ünsal, is found. The exact quantization condition of Zinn-Justin and Jentschura is equivalent to the Nekrasov-Shatashvili quantization condition on the level of the ensemble. Refined topological string theory in the Nekrasov-Shatashvili limit arises as a large N limit of quantum mechanics. © 2014 The Authors. Source


Ferrari R.,Center for Theoretical Physics | Ferrari R.,University of Milan
Acta Physica Polonica B | Year: 2012

In the present paper, we study the limit of zero mass in non-Abelian gauge theories both with Higgs mechanism and in the nonlinear realization of the gauge group (Stückelberg mass). We argue that in the first case the longitudinal modes undergo a metamorphosis process to the Goldstone scalar modes, while in the second, we guess, a decoupling process associated to a phase transformation. The two scenarios yield strikingly different behaviors at high energy, mainly ascribed to the presence of a massless Higgs doublet among the physical modes in the case of Higgs mechanism (i.e. not only the Higgs boson). The aim of this work is to show that the problem of unitarity at high energy in non-Abelian gauge theory with no Higgs boson can open new perspectives in quantum field theory. Source


Ferrari R.,National Institute of Nuclear Physics, Italy | Ferrari R.,Center for Theoretical Physics
Acta Physica Polonica B | Year: 2013

On the basis of extended simulations, we provide some results concerning the spectrum of Massive SU(2) Yang-Mills on the lattice. We study the "time" correlator of local gauge invariant operators integrated over the remaining three dimensions. The energy gaps are measured in the isospin I = 0,1 and internal spin J = 0,1 channels. No correlation is found in the I = 1, J = 0 channel. In the I = 1, J = 1 channel and far from the critical mass value mc, the energy gap roughly follows the bare valuem (vector mesons). In approaching the critical value mc at β fixed, there is a bifurcation of the energy gap: one branch follows the value m, while the new is much larger and it shows a more and more dominant weight. This phenomenon might be the sign of two important features: the long range correlation near the fixed point at β → ∞ implied by the low energy gap and the screening (or confining) mechanisms across the m = mc associated to the larger gap. The I = 0, J = 0,1 gaps are of the same order of magnitude, typically larger than the I = 1, J = 1 gap (for m > mc). For m ∼ m c, both I = 0 gaps have a dramatic drop with minima near the value m. This behavior might correspond to the formation of I = 0 bound states both in the J = 0 and J = 1 channels. Source


Janiuk A.,Center for Theoretical Physics | Czerny B.,pernicus Astronomical Center
Monthly Notices of the Royal Astronomical Society | Year: 2011

We discuss two important instability mechanisms that may lead to the limit-cycle oscillations of the luminosity of the accretion discs around compact objects: ionization instability and radiation pressure instability. Ionization instability is well established as a mechanism of X-ray novae eruptions in black hole binary systems, but its applicability to active galactic nuclei (AGN) is still problematic. Radiation pressure theory has still a very weak observational background in any of these sources. In this paper, we attempt to confront the parameter space of these instabilities with the observational data. At the basis of this simple survey of sources properties, we argue that the radiation pressure instability is likely to be present in several Galactic sources with the Eddington ratios being above 0.15 and in AGN with the Eddington ratio above 0.025. Our results favour the parametrization of the viscosity through the geometrical mean of the radiation and gas pressure in both Galactic sources and AGN. More examples of the quasi-regular outbursts in the time-scales of 100 s in Galactic sources and hundreds of years in AGN are needed to formulate firm conclusions. We also show that the disc sizes in the X-ray novae are consistent with the ionization instability. This instability may also considerably influence the lifetime cycle and overall complexity in the supermassive black hole environment. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS. Source


Sanders J.L.,Center for Theoretical Physics | Sanders J.L.,Institute of Astronomy | Binney J.,Center for Theoretical Physics
Monthly Notices of the Royal Astronomical Society | Year: 2015

We extend models of our Galaxy based on distribution functions that are analytic functions of the action integrals to extended distribution functions (EDFs), which have an analytic dependence on metallicity as well. We use a simple, but physically motivated, functional forms for the metallicity of the interstellar medium as a function of radius and time and for the star formation rate, and a model for the diffusion of stars through phase space to suggest the required functional form of an EDF.We introduce a simple prescription for radial migration that preserves the overall profile of the disc while allowing individual stars to migrate throughout the disc. Our models explicitly consider the thin and thick discs as two distinct components separated in age.We show how an EDF can be used to incorporate realistic selection functions in models, and to construct mock catalogues of observed samples. We show that the selection function of the Geneva-Copenhagen Survey (GCS) biases in favour of young stars, which have atypically small random velocities. With the selection function taken into account our models produce good fits of the GCS data in chemo-dynamical space and the Gilmore & Reid (1983) density data. From our EDF, we predict the structure of the Sloan Extension for Galactic Understanding and Exploration G-dwarf sample. The kinematics are successfully predicted. The predicted metallicity distribution has too few stars with [Fe/H]≃-0.5 dex and too many metal-rich stars. A significant problem may be the lack of any chemical-kinematic correlations in our thick disc. We argue that EDFs will prove essential tools for the analysis of both observational data and sophisticated models of Galaxy formation and evolution. © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Source

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