81 research outputs found
Nucleon-Nucleon Scattering and Large N(c) QCD
Nucleon-nucleon scattering observables are discussed in the context of large
Nc QCD. As is well known, the baryon spectrum in the large Nc limit exhibits
contracted SU(2Nf) spin-flavor sym- metry. This symmetry can be used to derive
model-independent relations between proton-proton and proton-neutron total
cross sections. These relations are valid in the kinematic regime in which the
relative momentum of two nucleons is of order of Nc. In this semiclassical
regime the nucleon-nucleon scattering can be described in the time-dependent
mean field approximation. These model-independent results are compared to
experimental data for spin-independent and polarized total nucleon-nucleon
cross sections.Comment: 9 pages, 3 figures. Invited talk, Xth Quark Confinement and the
Hadron Spectrum, October 201
Heavy Baryons: A Combined Large N_c and Heavy Quark Expansion for Electroweak Currents
The combined large N_c and heavy quark limit for baryons containing a single
heavy quark is discussed. The combined large N_c and heavy quark expansion of
the heavy quark bilinear operators is obtained. In the combined expansion the
corrections proportional to m_N/m_Q are summed to all orders. In particular,
the combined expansion can be used to determine semileptonic form factors of
heavy baryons in the combined limit.Comment: 8 pages. Presented at The Phenomenology of Large N_c QCD, Tempe,
Arizona, 9-11 Jan 200
Classical Strongly Coupled QGP II: Screening and Equation of State
We analyze the screening and bulk energy of a classical and strongly
interacting plasma of color charges, a model we recently introduced for the
description of a quark-gluon plasma at T=(1-3)Tc. The partition function is
organized around the Debye-Huckel limit. The linear Debye-Huckel limit is
corrected by a virial expansion. For the pressure, the expansion is badly
convergent even in the dilute limit. The non-linear Debye-Huckel theory is
studied numerically as an alternative for moderately strong plasmas. We use
Debye theory of solid to extend the analysis to the crystal phase at very
strong coupling. The analytical results for the bulk energy per particle
compare well with the numerical results from molecular dynamics simulation for
all couplings.Comment: 9 pages, 5 figure
New near-threshold mesons
We show that under a number of rather plausible assumptions QCD spectrum may
contain a number of mesons which have not been predicted or observed. Such
states will have the quantum numbers of two existing mesons and masses very
close to the dissociation threshold into the two mesons. Moreover, at least one
of the two mesonic constituents itself must be very close to its dissociation
threshold. In particular, one might expect the existence of loosely bound
systems of and \D; similarly, and \ff, and \ff, and
and and can be bound. The mechanism for binding in these
cases is the S-wave kaon exchange. The nearness of one of the constituents to
its decay threshold into a kaon plus a remainder, implies that the range of the
kaon exchange force becomes abnormally long--significantly longer than
which greatly aids the binding.Comment: 5 page
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Rich state, poor state, red state, blue state: What's the matter with Connecticut?
For decades, the Democrats have been viewed as the party of the poor, with the Republicans representing the rich. Recent presidential elections, however, have shown a reverse pattern, with Democrats performing well in the richer blue states in the northeast and coasts, and Republicans dominating in the red states in the middle of the country and the south. Through multilevel modeling of individual-level survey data and county- and state-level demographic and electoral data, we reconcile these patterns. Furthermore, we find that income matters more in red America than in blue America. In poor states, rich people are much more likely than poor people to vote for the Republican presidential candidate, but in rich states (such as Connecticut), income has a very low correlation with vote preference
Classical Strongly Coupled QGP I: The Model and Molecular Dynamics Simulations
We propose a model for the description of strongly interacting quarks and
gluon quasiparticles at , as a classical and nonrelativistic
colored Coulomb gas. The sign and strength of the inter-particle interactions
are fixed by the scalar product of their classical {\it color vectors} subject
to Wong's equations. The model displays a number of phases as the Coulomb
coupling is increased ranging from a gas, to a liquid, to a crystal with
antiferromagnetic-like color ordering. We analyze the model using Molecular
Dynamics (MD) simulations and discuss the density-density correlator in real
time. We extract pertinent decorrelation times, diffusion and viscosity
constants for all phases. The classical results when extrapolated to the sQGP
suggest that the phase is liquid-like, with a diffusion constant and a bulk viscosity to entropy density ratio .Comment: 11 pages, 14 figure
Nucleon-Nucleon Scattering Observables in Large- QCD
Nucleon-nucleon scattering observables are considered in the context of the
large limit of QCD for initial states with moderately high momenta (). The scattering is studied in the framework of the time-dependent
mean-field approximation. We focus on the dependence of those observables on
the spin and isospin of the initial state which may be computed using
time-dependent mean-field theory. We show that, up to corrections, all such
observables must be invariant under simultaneous spin and isospin flips ({\it
i.e.} rotations through in both spin and isospin) acting on either
particle. All observables of this class obtained from spin unpolarized
measurements must be isospin independent up to corrections. Moreover,
it can be shown that the leading correction is of relative order
rather than .Comment: 4 page
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