Search results for "REPRESENTATION"
showing 10 items of 1710 documents
Examples of pseudo-bosons in quantum mechanics
2010
We discuss two physical examples of the so-called {\em pseudo-bosons}, recently introduced in connection with pseudo-hermitian quantum mechanics. In particular, we show that the so-called {\em extended harmonic oscillator} and the {\em Swanson model} satisfy all the assumptions of the pseudo-bosonic framework introduced by the author. We also prove that the biorthogonal bases they produce are not Riesz bases.
Solution of the Lindblad equation in Kraus representation
2006
The so-called Lindblad equation, a typical master equation describing the dissipative quantum dynamics, is shown to be solvable for finite-level systems in a compact form without resort to writing it down as a set of equations among matrix elements. The solution is then naturally given in an operator form, known as the Kraus representation. Following a few simple examples, the general applicability of the method is clarified.
Systematic construction of spin liquids on the square lattice from tensor networks with SU(2) symmetry
2016
We elaborate a simple classification scheme of all rank-5 SU(2)-spin rotational symmetric tensors according to i) the on-site physical spin-$S$, (ii) the local Hilbert space $V^{\otimes 4}$ of the four virtual (composite) spins attached to each site and (iii) the irreducible representations of the $C_{4v}$ point group of the square lattice. We apply our scheme to draw a complete list of all SU(2)-symmetric translationally and rotationally-invariant Projected Entangled Pair States (PEPS) with bond dimension $D\leqslant 6$. All known SU(2)-symmetric PEPS on the square lattice are recovered and simple generalizations are provided in some cases. More generally, to each of our symmetry class can…
The strong coupling from ALEPH tau decays
2017
The strong coupling from ALEPH tau decays. We use the publically available non-strange spectral function from ALEPH tau decays to critically analyze the different determinations of αs(mτ2) that can be found in the literature and the numerical impact of their possible weaknesses. We also introduce some novel approaches. We find that perturbative uncertainties dominate. Our results with different approaches are very stable. Our final value is αs(mτ2)=0.328±0.013.
Identifying spin and parity of charmonia in flight with lattice QCD
2019
The spectrum of charmonium resonances contains a number of unanticipated states along with several conventional quark-model excitations. The hadrons of different quantum numbers $J^P$ appear in a fairly narrow energy band, where $J^P$ refers to the spin-parity of a hadron at rest. This poses a challenge for Lattice QCD studies of (coupled-channel) meson-meson scattering aimed at the determination of scattering amplitudes and resonance pole positions. A wealth of information for this purpose can be obtained from the lattice spectra in frames with nonzero total momentum. These are particularly dense since hadrons with different $J^P$ contribute to any given lattice irreducible representation.…
Nonperturbative Determination of the QCD Potential atO(1/m)
2006
The relativistic correction to the QCD static interquark potential at O(1/m) is investigated nonperturbatively for the first time by using lattice Monte Carlo QCD simulations. The correction is found to be comparable with the Coulombic term of the static potential when applied to charmonium, and amounts to one-fourth of the Coulombic term for bottomonium.
Noncompact Topological Quantum Groups
1995
A star-product construction of quantum semisimple real Lie groups is performed for the noncompact case.
Quarkonium spectral functions with complex potential
2011
Abstract We study quarkonium spectral functions at high temperatures using a potential model with complex potential. The real part of the potential is constrained by the lattice QCD data on static quark anti-quark correlation functions, while the imaginary part of the potential is taken from perturbative calculations. We find that the imaginary part of the potential has significant effect on quarkonium spectral functions, in particular, it leads to the dissolution of the 1S charmonium and excited bottomonium states at temperatures about 250 MeV and melting of the ground state bottomonium at temperatures slightly above 450 MeV.
FITTING LAW FOR THE DENSITY SHIFT OF Q(J) TRANSITIONS OF H2 IN H2–X (X: H2, He, N2) MIXTURES
1998
Abstract A variety of fitting laws have been developed for the purpose of modelling broadening effects in collisional processes, but only a few have been proposed for modelling collision-induced lineshifts in molecules. We analysed accurate stimulated Raman data obtained in several H2–X mixtures (X: H2, He and N2). For the first time, we show that an empirical law provides a very good representation of collisional lineshift coefficients in the range 300–1200 K and for J quantum number up to 9.
Classical anomalies of supersymmetric extended objects
1991
Abstract The hamiltonian form of the action for a p-extended supersymmetric object is presented, and used to deduce both the algebra generated by the constraints, in agreement with previous results for p=1,2, and the algebra of the supersymmetry charges. The “anomalous” contributions in each algebra (for given p) are shown to be related, and the origin of their different properties is exhibited. In particular, it is shown why only in the charge algebra are the “anomalous” contributions always topological and the commutators of the translations always zero.