Boson star with particle size effects

A simple model to study boson stars is to consider these stellar objects as quantum systems of $N$ identical self-gravitating particles within a non-relativistic framework. Some results obtained with point-like particles are recalled as well as the validity limits of this model. Approximate analytical calculations are performed using envelope theory for a truncated Coulomb-like potential simulating a particle size. If the boson mass is sufficiently small, the description of small mass boson stars is possible within non-relativistic formalism. The mass and radius of these stellar objects are strongly dependent on the value of the truncation parameter.Comment: Proceedings of the Workshop in honour of the 65th birthday of Professor Philippe Spindel (UMONS, 2015

Bound cyclic systems with the envelope theory

Approximate but reliable solutions of a quantum system with $N$ identical particles can be easily computed with the envelope theory, also known as the auxiliary field method. This technique has been developed for Hamiltonians with arbitrary kinematics and one- or two-body potentials. It is adapted here for cyclic systems with $N$ identical particles, that is to say systems in which a particle $i$ has only an interaction with particles $i-1$ and $i+1$ (with $N+1\equiv 1$)

Mass formula for strange baryons in large NcN_c QCD versus quark model

A previous work establishing a connection between a quark model, with relativistic kinematics and a $Y$-confinement plus one gluon exchange, and the $1/N_c$ expansion mass formula is extended to strange baryons. Both methods predict values for the SU(3)-breaking mass terms which are in good agreement with each other. Strange and nonstrange baryons are shown to exhibit Regge trajectories with an equal slope, but with an intercept depending on the strangeness. Both approaches agree on the value of the slope and of the intercept and on the existence of a single good quantum number labeling the baryons within a given Regge trajectory.Comment: 2 figure

Comment on `Glueball spectrum from a potential model'

In a recent article, W.-S. Hou and G.-G. Wong [Phys. Rev. D {\bf 67}, 034003 (2003)] have investigated the spectrum of two-gluon glueballs below 3 GeV in a potential model with a dynamical gluon mass. We point out that, among the 18 states calculated by the authors, only three are physical. The other states either are spurious or possess a finite mass only due to an arbitrary restriction of the variational parameter.Comment: Comment on pape

Observer with a constant proper acceleration

Relying on the equivalence principle, a first approach of the general theory of relativity is presented using the spacetime metric of an observer with a constant proper acceleration. Within this non inertial frame, the equation of motion of a freely moving object is studied and the equation of motion of a second accelerated observer with the same proper acceleration is examined. A comparison of the metric of the accelerated observer with the metric due to a gravitational field is also performed.Comment: 5 figure

Towers of hybrid mesons

A hybrid meson is a quark-antiquark pair in which, contrary to ordinary mesons, the gluon field is in an excited state. In the framework of constituent models, the interaction potential is assumed to be the energy of an excited string. An approximate, but accurate, analytical solution of the Schr\"{o}dinger equation with such a potential is presented. When applied to hybrid charmonia and bottomonia, towers of states are predicted in which the masses are a linear function of a harmonic oscillator band number for the quark-antiquark pair. Such a formula could be a reliable guide for the experimental detection of heavy hybrid mesons.Comment: 3 figure

The SUSY Yang-Mills plasma in a TT-matrix approach

The thermodynamic properties of ${\cal N}=1$ supersymmetric Yang-Mills theory with an arbitrary gauge group are investigated. In the confined range, we show that identifying the bound state spectrum with a Hagedorn one coming from non-critical closed superstring theory leads to a prediction for the value of the deconfining temperature $T_c$ that agrees with recent lattice data. The deconfined phase is studied by resorting to a $T$-matrix formulation of statistical mechanics in which the medium under study is seen as a gas of quasigluons and quasigluinos interacting nonperturbatively. Emphasis is put on the temperature range (1-5)~$T_c$, where the interaction are expected to be strong enough to generate bound states. Binary bound states of gluons and gluinos are indeed found to be bound up to 1.4 $T_c$ for any gauge group. The equation of state is then computed numerically for SU($N$) and $G_2$, and discussed in the case of an arbitrary gauge group. It is found to be nearly independent of the gauge group and very close to that of non-supersymmetric Yang-Mills when normalized to the Stefan-Boltzmann pressure and expressed as a function of $T/T_c$.Comment: The main conclusions of our previous versions are unchanged. This version is improved and is a fusion of our papers arXiv:1408.0958v2 and arXiv:1408.497

(2+1)(2+1)-dd Glueball Spectrum within a Constituent Picture

The quantum numbers and mass hierarchy of the glueballs observed in $(2+1)$-dimensional lattice QCD with gauge group SU($N_c$) are shown to be in agreement with a constituent picture. The agreement is maintained when going from glueballs to gluelumps, and when the gauge group SO($2N_c$) is taken instead of SU($N_c$)