2,972 research outputs found
QCD Quark Condensate from SUSY and the Orientifold Large-N Expansion
We estimate the quark condensate in one-flavor massless QCD from the known
value of the gluino condensate in SUSY Yang-Mills theory using our newly
proposed "orientifold" large-N expansion. The numerical result for the quark
condensate renormalized at the scale 2 GeV is then given as a function of
alpha_s(2 GeV) and of possible corrections from sub-leading terms. Our value
can be compared with the quark condensate in (quenched) lattice QCD or with the
one extracted from the Gell-Mann--Oakes--Renner relation by virtue of
non-lattice determinations of the quark masses. In both cases we find quite a
remarkable agreement.Comment: 15 pages, LaTe
Exact Results on the Space of Vacua of Four Dimensional SUSY Gauge Theories
We consider four dimensional quantum field theories which have a continuous
manifold of inequivalent exact ground states -- a moduli space of vacua.
Classically, the singular points on the moduli space are associated with extra
massless particles. Quantum mechanically these singularities can be smoothed
out. Alternatively, new massless states appear there. These may be the
elementary massless particles or new massless bound states.Comment: 19 pages, RU-94-1
Lattice Perturbation Theory by Computer Algebra: A Three-Loop Result for the Topological Susceptibility
We present a scheme for the analytic computation of renormalization functions
on the lattice, using a symbolic manipulation computer language. Our first
nontrivial application is a new three-loop result for the topological
susceptibility.Comment: 15 pages + 2 figures (PostScript), report no. IFUP-TH 31/9
Seiberg Duality and e+ e- Experiments
Seiberg duality in supersymmetric gauge theories is the claim that two
different theories describe the same physics in the infrared limit. However,
one cannot easily work out physical quantities in strongly coupled theories and
hence it has been difficult to compare the physics of the electric and magnetic
theories. In order to gain more insight into the equivalence of two theories,
we study the ``e+ e-'' cross sections into ``hadrons'' for both theories in the
superconformal window. We describe a technique which allows us to compute the
cross sections exactly in the infrared limit. They are indeed equal in the
low-energy limit and the equality is guaranteed because of the anomaly matching
condition. The ultraviolet behavior of the total ``e+ e-'' cross section is
different for the two theories. We comment on proposed non-supersymmetric
dualities. We also analyze the agreement of the ``\gamma\gamma'' and ``WW''
scattering amplitudes in both theories, and in particular try to understand if
their equivalence can be explained by the anomaly matching condition.Comment: 24 pages, 2 figures, uses psfi
Collective Fluorescence Enhancement In Nanoparticle Clusters
Many nanoscale systems are known to emit light intermittently under continuous illumination. In the fluorescence of single semiconductor nanoparticles, the distributions of bright and dark periods (\u27on\u27 and \u27off\u27 times) follow Levy statistics. Although fluorescence from single-quantum dots and from macroscopic quantum dot ensembles has been studied, there has been little study of fluorescence from small ensembles. Here we show that blinking nanorods (NRs) interact with each other in a cluster, and the interactions affect the blinking statistics. The on-times in the fluorescence of a NR cluster increase dramatically; in a cluster with N NRs, the maximum on-time increases by a factor of N or more compared with the combined signal from N well-separated NRs. Our study emphasizes the use of statistical properties in identifying the collective dynamics. The scaling of this interaction-induced increase of on-times with number of NRs reveals a novel collective effect at the nanoscale
Explicitly solvable cases of one-dimensional quantum chaos
We identify a set of quantum graphs with unique and precisely defined
spectral properties called {\it regular quantum graphs}. Although chaotic in
their classical limit with positive topological entropy, regular quantum graphs
are explicitly solvable. The proof is constructive: we present exact periodic
orbit expansions for individual energy levels, thus obtaining an analytical
solution for the spectrum of regular quantum graphs that is complete, explicit
and exact
The New Fat Higgs: Slimmer and More Attractive
In this paper we increase the MSSM tree level higgs mass bound to a value
that is naturally larger than the LEP-II search constraint by adding to the
superpotential a term, as in the NMSSM, and UV
completing with new strong dynamics {\it before} becomes
non-perturbative. Unlike other models of this type the higgs fields remain
elementary, alleviating the supersymmetric fine-tuning problem while
maintaining unification in a natural way.Comment: 14 pages and 2 figures. Added references and updated argument about
constraints from reheating temperatur
Theory for the single-point velocity statistics of fully developed turbulence
We investigate the single-point velocity probability density function (PDF)
in three-dimensional fully developed homogeneous isotropic turbulence within
the framework of PDF equations focussing on deviations from Gaussianity. A
joint analytical and numerical analysis shows that these deviations may be
quantified studying correlations of dynamical quantities like pressure
gradient, external forcing and energy dissipation with the velocity. A
stationary solution for the PDF equation in terms of these quantities is
presented, and the theory is validated with the help of direct numerical
simulations indicating sub-Gaussian tails of the PDF.Comment: 6 pages, 4 figures, corrected typo in eq. (4
Chirally Symmetric Phase of Supersymmetric Gluodynamics
We argue that supersymmetric gluodynamics (theory of gluons and gluinos) has
a condensate-free phase. Unlike the standard phase, the discrete axial symmetry
of the Lagrangian is unbroken in this phase, and the gluino condensate does not
develop. Extra unconventional vacua are supersymmetric and are characterized by
the presence of (bosonic and fermionic) massless bound states. A set of
arguments in favor of the conjecture includes: (i) analysis of the effective
Lagrangian of the Veneziano-Yankielowicz type which we amend to properly
incorporate all symmetries of the model; (ii) consideration of an unsolved
problem with the Witten index; (iii) interpretation of a mismatch between the
strong-coupling and weak coupling instanton calculations of the gluino
condensate detected previously. Impact on Seiberg's results is briefly
discussed.Comment: Minor typos corrected; final version to appear in Phys. Rev.
Quantum geometrodynamics for black holes and wormholes
The geometrodynamics of the spherical gravity with a selfgravitating thin
dust shell as a source is constructed. The shell Hamiltonian constraint is
derived and the corresponding Schroedinger equation is obtained. This equation
appeared to be a finite differences equation. Its solutions are required to be
analytic functions on the relevant Riemannian surface. The method of finding
discrete spectra is suggested based on the analytic properties of the
solutions. The large black hole approximation is considered and the discrete
spectra for bound states of quantum black holes and wormholes are found. They
depend on two quantum numbers and are, in fact, quasicontinuous.Comment: Latex, 32 pages, 5 fig
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