Search results for "REPRESENTATION"
showing 10 items of 1710 documents
Construction of pseudo-bosons systems
2010
In a recent paper we have considered an explicit model of a PT-symmetric system based on a modification of the canonical commutation relation. We have introduced the so-called {\em pseudo-bosons}, and the role of Riesz bases in this context has been analyzed in detail. In this paper we consider a general construction of pseudo-bosons based on an explicit {coordinate-representation}, extending what is usually done in ordinary supersymmetric quantum mechanics. We also discuss an example arising from a linear modification of standard creation and annihilation operators, and we analyze its connection with coherent states.
Kac-Moody group representations and generalization of the Sugawara construction of the Virasoro algebra
1988
We discuss the dynamical structure of the semidirect product of the Virasoro and affine Kac-Moody groups within the framework of a group quantization formalism. This formalism provides a realization of the Virasoro algebra acting on Kac-Moody Fock states which generalizes the Sugawara construction. We also give an explicit construction of the standard Kac-Moody group representations associated with strings on SU(2) and recover, in particular, the ‘renormalization’ β factor of L(z)
Charmonium properties in hot quenched lattice QCD
2012
We study the properties of charmonium states at finite temperature in quenched QCD on large and fine isotropic lattices. We perform a detailed analysis of charmonium correlation and spectral functions both below and above $T_c$. Our analysis suggests that both S wave states ($J/\psi$ and $\eta_c$) and P wave states ($\chi_{c0}$ and $\chi_{c1}$) disappear already at about $1.5 T_c$. The charm diffusion coefficient is estimated through the Kubo formula and found to be compatible with zero below $T_c$ and approximately $1/\pi T$ at $1.5 T_c\lesssim T\lesssim 3 T_c$.
Two-flavour lattice QCD correlation functions in the deconfinement transition region
2013
We report on a lattice QCD calculation with two dynamical flavors of the isovector vector correlator in the high-temperature phase. We analyze the correlator in terms of the associated spectral function by performing a fit for the difference of the thermal and vacuum spectral functions, using also an exact sum rule that constrains this difference. Additonally we carry out a direct fit for the thermal spectral function, and obtain good agreement between the two analyses for frequencies below the two-pion threshold. Under the assumption that the spectral function is smooth in that region, we give an estimate of the electrical conductivity.
Effective Lagrangians for QCD: Deconfinement and Chiral Symmetry Restoration
2004
Effective Lagrangians for Quantum Chromodynamics (QCD) especially suited for understanding deconfinement and chiral symmetry restoration at nonzero temperature and matter density are reviewed. These effective theories allow one to study generic properties of phase transitions using non-order parameter fields without loosing the information encoded in the true order parameter. {}For the pure gauge theory we demonstrate that, near the deconfining phase transition, the center group symmetry is naturally linked to the conformal anomaly. Another relevant outcome is that when the theory contains also quarks we can explain the intertwining of chiral symmetry restoration and deconfinement for QCD w…
Non-Markovianity of Gaussian Channels
2015
We introduce a necessary and sufficient criterion for the non-Markovianity of Gaussian quantum dynamical maps based on the violation of divisibility. The criterion is derived by defining a general vectorial representation of the covariance matrix which is then exploited to determine the condition for the complete positivity of partial maps associated to arbitrary time intervals. Such construction does not rely on the Choi-Jamiolkowski representation and does not require optimization over states.
Quantum deformations of singletons and of free zero-mass fields
1993
We consider quantum deformations of the real symplectic (or anti-De Sitter) algebra sp(4), ℝ ≅ spin(3, 2) and of its singleton and (4-dimensional) zero-mass representations. For q a root of −1, these representations admit finite-dimensional unitary subrepresentations. It is pointed out that Uq(sp(4, ℝ)), unlike Uq(su(2, 2)), contains Uq(sl2) as a quantum subalgebra.
Modular symmetry origin of texture zeros and quark-lepton unification
2020
The even weight modular forms of level $N$ can be arranged into the common irreducible representations of the inhomogeneous finite modular group $\Gamma_N$ and the homogeneous finite modular group $\Gamma'_N$ which is the double covering of $\Gamma_N$, and the odd weight modular forms of level $N$ transform in the new representations of $\Gamma'_N$. We find that the above structure of modular forms can naturally generate texture zeros of the fermion mass matrices if we properly assign the representations and weights of the matter fields under the modular group. We perform a comprehensive analysis for the $\Gamma'_3\cong T'$ modular symmetry. The three generations of left-handed quarks are a…
Charmonium dissociation and heavy quark transport in hot quenched lattice QCD
2012
We study the properties of charmonium states at finite temperature in quenched lattice QCD on large and fine isotropic lattices. We perform a detailed analysis of charmonium correlation and spectral functions both below and above Tc. Our analysis suggests that the S wave states disappear at about 1.5 Tc. The charm diffusion coefficient is estimated and found to be approximately 1/{\pi}T at 1.5Tc {\leq} T {\leq} 3Tc.
About two equivalent descriptions of quark antisymmetrization
1992
We analyze the wave function for a two-hadron system when the quark symmetrization principle is incorporated. Two alternative mathematical descriptions are considered. The representation method of Hund constructs a system of generators of thesinglet⊗singlet type. The method of Young-Froebenius incorporates hidden-color components in order to describe the representation basis. By taking a naive model we show that the two descriptions, are equivalent and thus no physical meaning should be attached to their mathematical differences. The results of our analysis are then applied to the more realisticN-N (deuteron) system. We end by discussing the structure of the Pauli correlations which we comp…