12 research outputs found
Moyal Brackets in M-Theory
The infinite limit of Matrix Theory in 4 and 10 dimensions is described in
terms of Moyal Brackets. In those dimensions there exists a Bogomol'nyi bound
to the Euclideanized version of these equations, which guarantees that
solutions of the first order equations also solve the second order Matrix
Theory equations. A general construction of such solutions in terms of a
representation of the target space co-ordinates as non-local spinor bilinears,
which are generalisations of the standard Wigner functions on phase space, is
given.Comment: 10 pages, Latex, no figures. References altered, typos correcte
Stabilization of the Yang-Mills chaos in non-Abelian Born-Infeld theory
We investigate dynamics of the homogeneous time-dependent SU(2) Yang-Mills
fields governed by the non-Abelian Born-Infeld lagrangian which arises in
superstring theory as a result of summation of all orders in the string slope
parameter . It is shown that generically the Born-Infeld dynamics is
less chaotic than that in the ordinary Yang-Mills theory, and at high enough
field strength the Yang-Mills chaos is stabilized. More generally, a smothering
effect of the string non-locality on behavior of classical fields is
conjectured.Comment: 7 pages, 5 figure
J/psi couplings to charmed resonances and to pi
We present an evaluation of the strong couplings JD^(*)D^(*) and
JD^(*)D^(*)pi by an effective field theory of quarks and mesons. These
couplings are necessary to calculate pi+J/psi --> D^(*)+barD^(*) cross
sections, an important background to the J/psi suppression signal in the
quark-gluon plasma. We write down the general effective lagrangian and compute
the relevant couplings in the soft pion limit and beyond.Comment: 11 pages, 4 figures, 2 reference added and minor comments, style
changed to RevTe
J/Psi suppression in colliding nuclei: statistical model analysis
We consider the suppression at a high energy heavy ion collision. An
ideal gas of massive hadrons in thermal and chemical equilibrium is formed in
the central region. The finite-size gas expands longitudinally in accordance
with Bjorken law. The transverse expansion in a form of the rarefaction wave is
taken into account. We show that suppression in such an environment,
when combined with the disintegration in nuclear matter, gives correct
evaluation of NA38 and NA50 data in a broad range of initial energy densities.Comment: 14 pages, 13 figures. Accepted for publication in Phys. Rev.
Multiplicity Distributions and Rapidity Gaps
I examine the phenomenology of particle multiplicity distributions, with
special emphasis on the low multiplicities that are a background in the study
of rapidity gaps. In particular, I analyze the multiplicity distribution in a
rapidity interval between two jets, using the HERWIG QCD simulation with some
necessary modifications. The distribution is not of the negative binomial form,
and displays an anomalous enhancement at zero multiplicity. Some useful
mathematical tools for working with multiplicity distributions are presented.
It is demonstrated that ignoring particles with pt<0.2 has theoretical
advantages, in addition to being convenient experimentally.Comment: 24 pages, LaTeX, MSUHEP/94071
The Finite Temperature SU(2) Savvidy Model with a Non-trivial Polyakov Loop
We calculate the complete one-loop effective potential for SU(2) gauge bosons
at temperature T as a function of two variables: phi, the angle associated with
a non-trivial Polyakov loop, and H, a constant background chromomagnetic field.
Using techniques broadly applicable to finite temperature field theories, we
develop both low and high temperature expansions. At low temperatures, the real
part of the effective potential V_R indicates a rich phase structure, with a
discontinuous alternation between confined (phi=pi) and deconfined phases
(phi=0). The background field H moves slowly upward from its zero-temperature
value as T increases, in such a way that sqrt(gH)/(pi T) is approximately an
integer. Beyond a certain temperature on the order of sqrt(gH), the deconfined
phase is always preferred. At high temperatures, where asymptotic freedom
applies, the deconfined phase phi=0 is always preferred, and sqrt(gH) is of
order g^2(T)T. The imaginary part of the effective potential is non-zero at the
global minimum of V_R for all temperatures. A non-perturbative magnetic
screening mass of the form M_m = cg^2(T)T with a sufficiently large coefficient
c removes this instability at high temperature, leading to a stable
high-temperature phase with phi=0 and H=0, characteristic of a
weakly-interacting gas of gauge particles. The value of M_m obtained is
comparable with lattice estimates.Comment: 28 pages, 5 eps figures; RevTeX 3 with graphic
Closed-flavor pi + J/psi and pi + Upsilon Cross Sections at Low Energies from Dipion Decays
The scale of low energy c-cbar and b-bbar cross sections on light hadrons is
of great importance to searches for the quark gluon plasma using the
heavy-quarkonium suppression signature. Unfortunately, little is known about
these near-threshold cross sections at present, and recent theoretical
estimates span many orders of magnitude. Here we use experimental data on the
four observed closed-flavor heavy quarkonium hadronic decays psi' -> pi pi
J/psi, Upsilon' -> pi pi Upsilon, Upsilon'' -> pi pi Upsilon and Upsilon'' ->
pi pi Upsilon', combined with simple models of the transition amplitudes, to
estimate the pion scattering cross sections of c-cbar and b-bbar mesons near
threshold. Specifically we consider the closed-flavor reactions pi J/psi -> pi
psi', pi Upsilon -> pi Upsilon', pi Upsilon -> pi Upsilon'' and pi Upsilon' ->
pi Upsilon'' and their time-reversed analogues. Our results may be useful in
constraining theoretical models of the strong interactions of heavy quarkonia,
and can be systematically improved through future detailed studies of dipion
decays, notably psi' -> pi pi J/psi and Upsilon'' -> pi pi Upsilon.Comment: 6 pages, 6 figure