1,125 research outputs found
Mesonic Spectra of Bosonized QCD_2 Models
We discuss bosonized two-dimensional QCD with massless fermions in the
adjoint and multi-flavor fundamental representations. We evaluate the massive
mesonic spectra of several models by using the light-front quantization and
diagonalizing the mass operator . We recover previous results in
the case of one flavor adjoint fermions and we find the exact massive spectrum
of multi flavor QCD in the limit of large number of flavors.Comment: 17 pages, Late
The string tension in massive
We compute the string tension in massive . It is shown that the string
tension vanishes when the mass of the dynamical quark is zero, with no
dependence on the representations of the dynamical or of the external charges.
When a small mass () is added, a tension appears and we calculate its
value as a function of the representations.Comment: 10 pages, Late
Screening and confinement in large N_f QCD_2 and in N=1 SYM_2
The screening nature of the potential between external quarks in massless
is derived using an expansion in - the number of
flavors. Applying the same method to the massive model, we find a confining
potential. We consider the N=1 super Yang Mills theory, reveal certain
problematic aspects of its bosonized version and show the associated screening
behavior by applying a point splitting method to the scalar current.Comment: 23 pages, Latex. 1 figur
The spectrum of multi-flavor QCD_2 and the non-Abelian Schwinger equation
Massless is dominated by classical configurations in the large
limit. We use this observation to study the theory by finding solutions to
equations of motion, which are the non-Abelian generalization of the Schwinger
equation. We find that the spectrum consists of massive mesons with which correspond to Abelian solutions. We generalize previously
discovered non-Abelian solutions and discuss their interpretation. We prove a
no-go theorem ruling out the existence of soliton solutions. Thus the
semi-classical approximation shows no baryons in the case of massless quarks, a
result derived before in the strong-coupling limit only.Comment: 17 pages, Latex. 1 figur
The spectrum of states with one current acting on the adjoint vacuum of massless QCD2
We consider a ``one current'' state, which is obtained by the application of
a color current on the ``adjoint'' vacuum. This is done in , with the
underlying quarks in the fundamental representation. The quarks are taken to be
massless, in which case the theory on the light-front can be ``currentized'',
namely, formulated in terms of currents only. The adjoint vacuum is shown to be
the application of a current derivative, at zero momentum, on the singlet
vacuum. We apply the operator on these states and find that in
general they are not eigenstates of apart from the large limit.
Problems with infra-red regularizations are pointed out. We discuss the
fermionic structure of these states.Comment: 18 pages, no figures. v2: minor corrections. v3: added some
clarifications and remarks, mainly on the contribution of zero modes. Typos
corrected, references added. To appear in Nuclear Physics
Screening in Supersymmetric Gauge Theories in Two Dimensions
We show that the string tension in N=1 two-dimensional super Yang-Mills
theory vanishes independently of the representation of the quark anti-quark
external source. We argue that this result persists in SQCD_2 and in
two-dimensional gauge theories with extended supersymmetry or in chiral
invariant models with at least one massless dynamical fermion. We also compute
the string tension for the massive Schwinger model, as a demonstration of the
method of the calculation.Comment: 8 pages, Latex. Minor changes. Accepted to Phys.Lett.
Subtleties in QCD theory in Two Dimensions
It is shown that in a formulation of Yang-Mills theory in two dimensions in
terms of A=if^{-1}\pa f, \bar A=i\bar f\bpa\bar f^{-1} with ,
the complexification of , reveals
certain subtleties. ``Physical" massive color singlet states seem to exist.
When coupled to quarks the coupling constant is renormalized in such a
way that it vanishes for the pure Yang- Mills case. This renders the above
states massless and unphysical. In the abelian case, on the other hand, the
known results of the Schwinger model are reproduced with no need of such a
renormalization.
The massless theory is analyzed in similar terms and peculiar massive
states appear, with a mass of .Comment: 21 page
The String Tension in Two Dimensional Gauge Theories
We review and elaborate on properties of the string tension in
two-dimensional gauge theories. The first model we consider is massive QED in
the limit. We evaluate the leading string tension both in the
fermionic and bosonized descriptions. We discuss the next to leading
corrections in . The next-to-leading terms in the long distance behavior
of the quark-antiquark potential, are evaluated in a certain region of external
versus dynamical charges. The finite temperature behavior is also determined.
In we review the results for the string tension of quarks in cases with
dynamical quarks in the fundamental, adjoint, symmetric and antisymmetric
representations. The screening nature of is re-derived.Comment: 25 pages, Latex. v2: several changes, mainly in section
On the stability of quark solitons in QCD
We critically re-examine our earlier derivation of the effective low energy action for QCD in 4 dimensions with chiral fields transforming non-trivially under both color and flavor, using the method of anomaly integration. We find several changes with respect to our previous results, leading to much more compact expressions, and making it easier to compare with results of other approaches to the same problem. With the amended effective action, we find that there are no stable soliton solutions. In the context of the quark soliton program, we interpret this as an indication that the full low-energy effective action must include additional terms, reflecting possible modifications at short distances and/or the non-trivial structure of the gauge fields in the vacuum, such as \neq 0. Such terms are absent in the formalism based on anomaly integration
-models on the quantum group manifolds , , and infinitesimal trasformations
The differential and variational calculus on the group is
constructed. The spontaneous breaking symmetry in the WZNW model with
quantum group symmetry and in the -models with
, quantum group symmetry is considered.
The Lagrangian formalism over the quantum group manifolds is discussed. The
classical solution of {}-model is obtained.Comment: LaTex, 7 page
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