122 research outputs found
Statistical transmutation of quantum bosonic strings coupled to general four-dimensional Chern-Simons theory
A bosonic string coupled to the generalized Chern-Simons theory in 3+1D
acquires a magnetic field along itself, when it is closed, and a topological
charge at its extremity, when it is open. We construct the creation operators
for the full quantum field states associated to these strings and determine the
dual algebra satisfied by them. We show that the creation operator fo the
composite state of a quantum closed bosonic string, bearing a magnetic flux,
and a topologically charged open bosonic string, possesses generalized
statistics. The relation of our results with previous approaches to the problem
is also established.Comment: 4 pages, Revtex
Quantized Skyrmion Fields in 2+1 Dimensions
A fully quantized field theory is developped for the skyrmion topological
excitations of the O(3) symmetric CP-Nonlinear Sigma Model in 2+1D. The
method allows for the obtainment of arbitrary correlation functions of quantum
skyrmion fields. The two-point function is evaluated in three different
situations: a) the pure theory; b) the case when it is coupled to fermions
which are otherwise non-interacting and c) the case when an electromagnetic
interaction among the fermions is introduced. The quantum skyrmion mass is
explicitly obtained in each case from the large distance behavior of the
two-point function and the skyrmion statistics is inferred from an analysis of
the phase of this function. The ratio between the quantum and classical
skyrmion masses is obtained, confirming the tendency, observed in semiclassical
calculations, that quantum effects will decrease the skyrmion mass. A brief
discussion of asymptotic skyrmion states, based on the short distance behavior
of the two-point function, is also presented.Comment: Accepted for Physical Review
BF models, Duality and Bosonization on higher genus surfaces
The generating functional of two dimensional field theories coupled to
fermionic fields and conserved currents is computed in the general case when
the base manifold is a genus g compact Riemann surface. The lagrangian density
is written in terms of a globally defined 1-form and a
multi-valued scalar field . Consistency conditions on the periods of
have to be imposed. It is shown that there exist a non-trivial dependence of
the generating functional on the topological restrictions imposed to . In
particular if the periods of the field are constrained to take values , with any integer, then the partition function is independent of the
chosen spin structure and may be written as a sum over all the spin structures
associated to the fermions even when one started with a fixed spin structure.
These results are then applied to the functional bosonization of fermionic
fields on higher genus surfaces. A bosonized form of the partition function
which takes care of the chosen spin structure is obtainedComment: 17 page
Monopoles and flux strings from SU(2) adjoint scalars
We construct, in an SU(2) gauge theory with two adjoint scalars, flux strings
with monopoles attached at the ends. One scalar breaks SU(2) to U(1) and
produces monopoles, the other then breaks the U(1) and produces strings.
Dualizing, we write the theory in terms of effective string variables and show
that the flux in the string is exactly saturated by the monopoles at the ends.Comment: 12 pp. v2: added several references and reworded some statement
High Superconductivity, Skyrmions and the Berry Phase
It is here pointed out that the antiferromagnetic spin fluctuation may be
associated with a gauge field which gives rise to the antiferromagnetic ground
state chirality. This is associated with the chiral anomaly and Berry phase
when we consider the two dimensional spin system on the surface of a 3D sphere
with a monopole at the centre. This realizes the RVB state where spinons and
holons can be understood as chargeless spins and spinless holes attached with
magnetic flux. The attachment of the magnetic flux of the charge carrier
suggest, that this may be viewed as a skyrmion. The interaction of a massless
fermion representing a neutral spin with a gauge field along with the
interaction of a spinless hole with the gauge field enhances the
antiferromagnetic correlation along with the pseudogap at the underdoped
region. As the doping increases the antiferromagnetic long range order
disappears for the critical doping parameter . In this framework,
the superconducting pairing may be viewed as caused by skyrmion-skyrmion bound
states.Comment: 10 pages, accepted in Phys. Rev.
Relativistic particle dynamics in D=2+1
We propose a SUSY variant of the action for a massless spinning particles via
the inclusion of twistor variables. The action is constructed to be invariant
under SUSY transformations and -reparametrizations even when an
interaction field is including. The constraint analysis is achieved and the
equations of motion are derived. The commutation relations obtained for the
commuting spinor variables show that the particle states have
fractional statistics and spin. At once we introduce a possible massive term
for the non-interacting model.Comment: 11 page
Quantum Criticality and Superconductivity in Quasi-Two-Dimensional Dirac Electronic Systems
We present a theory describing the superconducting (SC) interaction of Dirac
electrons in a quasi-two-dimensional system consisting of a stack of N planes.
The occurrence of a SC phase is investigated both at T=0 and T\neq 0, in the
case of a local interaction, when the theory must be renormalized and also in
the situation where a natural physical cutoff is present in the system. In both
cases, at T=0, we find a quantum phase transition connecting the normal and SC
phases at a certain critical coupling. The phase structure is shown to be
robust against quantum fluctuations. The SC gap is determined for T=0 and T\neq
0, both with and without a physical cutoff and the interplay between the gap
and the SC order parameter is discussed. Our theory qualitatively reproduces
the SC phase transition occurring in the underdoped regime of the high-Tc
cuprates. This fact points to the possible relevance of Dirac electrons in the
mechanism of high-Tc superconductivity.Comment: To be published in Nuclear Physics, Section B. 24 pages, 4 figure
A Geometric Approach to Massive p-form Duality
Massive theories of abelian p-forms are quantized in a generalized
path-representation that leads to a description of the phase space in terms of
a pair of dual non-local operators analogous to the Wilson Loop and the 't
Hooft disorder operators. Special atention is devoted to the study of the
duality between the Topologically Massive and the Self-Dual models in 2+1
dimensions. It is shown that these models share a geometric representation in
which just one non local operator suffices to describe the observables.Comment: 26 pages, LaTeX. The discussion about the equivalence between the
Proca model and two seldual models, with opposite spins, was eliminated.
Typos correcte
Superconductivity in graphene stacks: from the bilayer to graphite
We study the superconducting phase transition, both in a graphene bilayer and
in graphite. For that purpose we derive the mean-field effective potential for
a stack of graphene layers presenting hopping between adjacent sheets. For
describing superconductivity, we assume there is an on-site attractive
interaction between electrons and determine the superconducting critical
temperature as a function of the chemical potential. This displays a
dome-shaped curve, in agreement with previous results for two-dimensional Dirac
fermions. We show that the hopping between adjacent layers increases the
critical temperature for small values of the chemical potential. Finally, we
consider a minimal model for graphite and show that the transition temperature
is higher than that for the graphene bilayer for small values of chemical
potential. This might explain why intrinsic superconductivity is observed in
graphite
Effective Action for QED with Fermion Self-Interaction in D=2 and D=3 Dimensions
In this work we discuss the effect of the quartic fermion self-interaction of
Thirring type in QED in D=2 and D=3 dimensions. This is done through the
computation of the effective action up to quadratic terms in the photon field.
We analyze the corresponding nonlocal photon propagators nonperturbatively in %
\frac{k}{m}, where k is the photon momentum and m the fermion mass. The poles
of the propagators were determined numerically by using the Mathematica
software. In D=2 there is always a massless pole whereas for strong enough
Thirring coupling a massive pole may appear . For D=3 there are three regions
in parameters space. We may have one or two massive poles or even no pole at
all. The inter-quark static potential is computed analytically in D=2. We
notice that the Thirring interaction contributes with a screening term to the
confining linear potential of massive QED_{2}. In D=3 the static potential must
be calculated numerically. The screening nature of the massive QED
prevails at any distance, indicating that this is a universal feature of % D=3
electromagnetic interaction. Our results become exact for an infinite number of
fermion flavors.Comment: Latex, 13 pages, 3 figure
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