1,470 research outputs found
Revisiting Critical Vortices in Three-Dimensional SQED
We consider renormalization of the central charge and the mass of the supersymmetric Abelian vortices in 2+1 dimensions. We obtain
supersymmetric theory in 2+1 dimensions by dimensionally reducing the SQED in 3+1 dimensions with two chiral fields carrying opposite charges.
Then we introduce a mass for one of the matter multiplets without breaking N=2
supersymmetry. This massive multiplet is viewed as a regulator in the large
mass limit. We show that the mass and the central charge of the vortex get the
same nonvanishing quantum corrections, which preserves BPS saturation at the
quantum level. Comparison with the operator form of the central extension
exhibits fractionalization of a global U(1) charge; it becomes 1/2 for the
minimal vortex. The very fact of the mass and charge renormalization is due to
a "reflection" of an unbalanced number of the fermion and boson zero modes on
the vortex in the regulator sector.Comment: 24 pages, 2 figures Minor modifications, reference adde
A Remark on Supersymmetric Bubbles and Spectrum Crossover
Using an exact expression for the domain wall tension in a supersymmetric
model we show that a spectrum crossover takes place in passing from weak to
strong coupling. In the weak coupling regime elementary excitations are the
lightest states, while in the strong coupling regime solitonic objects of a
special type -- bubbles -- assume the role of the lightest states. The
crossover occurs at \lambda^2/(4\pi) \sim 0.4.Comment: 6 p., 1 fi
Persistent Challenges of Quantum Chromodynamics
Unlike some models whose relevance to Nature is still a big question mark,
Quantum Chromodynamics will stay with us forever. Quantum Chromodynamics (QCD),
born in 1973, is a very rich theory supposed to describe the widest range of
strong interaction phenomena: from nuclear physics to Regge behavior at large
E, from color confinement to quark-gluon matter at high densities/temperatures
(neutron stars); the vast horizons of the hadronic world: chiral dynamics,
glueballs, exotics, light and heavy quarkonia and mixtures thereof, exclusive
and inclusive phenomena, interplay between strong forces and weak interactions,
etc. Efforts aimed at solving the underlying theory, QCD, continue. In a
remarkable entanglement, theoretical constructions of the 1970s and 1990s
combine with today's ideas based on holographic description and strong-weak
coupling duality, to provide new insights and a deeper understanding.Comment: Julius Edgar Lilienfeld Prize Lecture at the April Meeting of APS,
Dallas, TX, April 22-25, 2006; v.2: reference added; v.3: reference adde
Supersymmetry Inspired QCD Beta Function
We propose an all orders beta function for ordinary Yang-Mills theories with
or without fermions inspired by the Novikov-Shifman-Vainshtein-Zakharov beta
function of N=1 supersymmetric gauge theories. The beta function allows us to
bound the conformal window. When restricting to one adjoint Weyl fermion we
show how the proposed beta function matches the one of supersymmetric
Yang-Mills theory. The running of the pure Yang-Mills coupling is computed and
the deviation from the two loop result is presented. We then compare the
deviation with the one obtained from lattice data also with respect to the two
loop running.Comment: 17 pages and 3 figures. References Adde
The Three-Loop Lattice Free Energy
We calculate the free energy of SU(N) gauge theories on the lattice, to three
loops. Our result, combined with Monte Carlo data for the average plaquette,
gives a more precise estimate of the gluonic condensate.Comment: 5 pages + 2 figures (PostScript); report no. IFUP-TH 17/9
Quantum Fusion of Domain Walls with Fluxes
We study how fluxes on the domain wall world volume modify quantum fusion of
two distant parallel domain walls into a composite wall. The elementary wall
fluxes can be separated into parallel and antiparallel components. The parallel
component affects neither the binding energy nor the process of quantum merger.
The antiparallel fluxes, instead, increase the binding energy and, against
naive expectations, suppress quantum fusion. In the small flux limit we
explicitly find the bounce solution and the fusion rate as a function of the
flux. We argue that at large (antiparallel) fluxes there exists a critical
value of the flux (versus the difference in the wall tensions), which switches
off quantum fusion altogether. This phenomenon of flux-related wall
stabilization is rather peculiar: it is unrelated to any conserved quantity.
Our consideration of the flux-related all stabilization is based on
substantiated arguments that fall short of complete proof.Comment: 17 pages, 3 figure
Three-Loop Results on the Lattice
We present some new three-loop results in lattice gauge theories, for the
Free Energy and for the Topological Susceptibility. These results are an
outcome of a scheme which we are developing (using a symbolic manipulation
language), for the analytic computation of renormalization functions on the
lattice.Comment: (Contribution to Lattice-92 conference). 4 page
Comments on Diquarks, Strong Binding and a Large Hidden QCD Scale
We present arguments regarding diquarks possible role in low-energy hadron
phenomenology that escaped theorists' attention so far. Good diquarks, i.e. the
states of two quarks, are argued to have a two-component structure with
one of the components peaking at distances several times shorter than a typical
hadron size (a short-range core). This can play a role in solving two old
puzzles of the 't Hooft 1/N expansion: strong quark mass dependence of the
vacuum energy density and strong violations of the Okubo-Zweig-Iizuka (OZI)
rule in the quark-antiquark channels. In both cases empiric data defy
't Hooft's 1/N suppression. If good diquarks play a role at an intermediate
energy scale they ruin 't Hoofts planarity because of their mixed-flavor
composition. This new scale associated with the good diquarks may be related to
a numerically large scale discovered in [V. Novikov, M. Shifman, A. Vainshtein
and V. Zakharov, Nucl. Phys. B 191, 301 (1981)] in a number of phenomena mostly
related to vacuum quantum numbers and glueball channels. If SU(3) of bona fide QCD is replaced by SU(2), diquarks become
well-defined gauge invariant objects. Moreover, there is an exact symmetry
relating them to pions. In this limit predictions regarding good diquarks are
iron-clad. If passage from SU(2) to SU(3) does not
lead to dramatic disturbances, these predictions remain qualitatively valid in
bona fide QCD.Comment: 18 pages, 3 figures; journal version, minor change
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