A Gauge Field Theory for Continuous Spin Tachyons

We present a gauge field theory for unitary infinite dimensional tachyonic representations of the Poincar\'e group. It was obtained by a dimensional reduction from the gauge field theory for continuous spin particles in a cotangent bundle over Minkowski space-time. We discuss its BRST formulation and compute the partition function. Some cubic vertices are also presented and their properties discussed. In the massless limit the gauge theory for continuous spin tachyons reduces to the gauge theory for continuous spin particles.Comment: 22 pages, typos correcte

Noncommutative Supersymmetric Field Theories

We discuss some properties of noncommutative supersymmetric field theories which do not involve gauge fields. We concentrate on the renormalizability issue of these theories.Comment: 12 pages, updated version of a talk presented at the XXI Brazilian National Meeting on Particles and Fields, Sao Lorenco, MG, Oct. 23 - 26, 200

Duality in Noncommutative Maxwell-Chern-Simons Theory

Applying a master action technique we obtain the dual of the noncommutative Maxwell-Chern-Simons theory. The equivalence between the Maxwell-Chern-Simons theory and the self-dual model in commutative space-time does not survive in the non-commutative setting. We also point out an ambiguity in the Seiberg-Witten map.Comment: 10 pages; Fifth International Conference on Mathematical Methods in Physics, Rio de Janeiro, April 24-28, 2006; PoS documentclas

Remarks on a Gauge Theory for Continuous Spin Particles

We discuss in a systematic way the gauge theory for a continuous spin particle proposed by Schuster and Toro. We show that it is naturally formulated in a cotangent bundle over Minkowski spacetime where the gauge field depends on the spacetime coordinate ${x^\mu}$ and on a covector $\eta_\mu$. We discuss how fields can be expanded in $\eta_\mu$ in different ways and how these expansions are related to each other. The field equation has a derivative of a Dirac delta function with support on the $\eta$-hyperboloid $\eta^2+1=0$ and we show how it restricts the dynamics of the gauge field to the $\eta$-hyperboloid. We then show that on-shell the field carries one single irreducible unitary representation of the Poincar\'e group for a continuous spin particle. We also show how the field can be used to build a set of covariant equations found by Wigner describing the wave function of one-particle states for a continuous spin particle. Finally we show that it is not possible to couple minimally a continuous spin particle to a background abelian gauge field, and make some comments about the coupling to gravity.Comment: 21 pages, typos corrected, improved presentation of section VI, final versio

Gauge Theory Formulations for Continuous and Higher Spin Fields

We consider a gauge theory action for continuous spin particles formulated in a spacetime enlarged by an extra coordinate recently proposed by Schuster and Toro. It requires one scalar gauge field and has two local symmetries. We show that the local symmetries are reducible in the sense that the parameters also have a local symmetry. Using reducibility we get an action which has two scalar gauge fields and a reducible but simpler local symmetry. We then show how this action and equations of motion are related to previously proposed formulations for continuous spin particles and higher spin theories. We also discuss the physical contents of each formulation to reveal the physical degrees of freedom.Comment: 20 pages; typos corrected, added a improved discussion of the physical contents of each formulation; final version, typos correcte

Tunnelling of Pulsating Strings in Deformed Minkowski Spacetime

Using the WKB approximation we analyse the tunnelling of a pulsating string in deformed Minkowski spacetime

Quantization in Ads and the Ads/CFT Correspondence

The quantization of a scalar field in AdS leads to two kinds of normalizable modes, usually called regular and irregular modes. The regular one is easily taken into account in the standard prescription for the AdS/CFT correspondence. The irregular mode requires a modified prescription which we argue is not completely satisfactory. We discuss an alternative quantization in AdS which incorporates boundary terms in a natural way. Within this quantization scheme we present an improved prescription for the AdS/CFT correspondence which can be applied to both, regular and irregular modes. Boundary conditions other than Dirichlet are naturally treated in this new improved setting.Comment: 8 pages. Contribution to the Proceedings of the Second Londrina Winter School "Mathematical Methods in Physics", August 25-30, 2002, Londrina, PR, Brazil; v2: typos correcte