Antisymmetric Tensor Potential Research Articles

D-instanton induced interactions on a D3-brane

Non-perturbative features of the derivative expansion of the effective action of a single D3-brane are obtained by considering scattering amplitudes of open and closed strings. This motivates expressions for the coupling constant dependence of world-volume interactions of the form $(\partial F)^4$ (where F is the Born-Infeld field strength), $(\partial^2\phi)^4$ (where $\phi$ are the normal coordinates of the D3-brane) and other interactions related by $\calN=4$ supersymmetry. These include terms that transform with non-trivial modular weight under Montonen-Olive duality. The leading D-instanton contributions that enter into these effective interactions are also shown to follow from an explicit stringy construction of the moduli space action for the D-instanton/D3-brane system in the presence of D3-brane open-string sources (but in the absence of a background antisymmetric tensor potential). Extending this action to include closed-string sources leads to a unified description of non-perturbative terms in the effective action of the form (embedding curvature)$^2$ together with open-string interactions that describe contributions of the second fundamental form.

Dynamical non-Abelian two-form: BRST quantization

When an antisymmetric tensor potential is coupled to the field strength of a gauge field via a $B\wedge F$ coupling and a kinetic term for $B$ is included, the gauge field develops an effective mass. The theory can be made invariant under a non-abelian vector gauge symmetry by introducing an auxiliary vector field. The covariant quantization of this theory requires ghosts for ghosts. The resultant theory including gauge fixing and ghost terms is BRST-invariant by construction, and therefore unitary. The construction of the BRST-invariant action is given for both abelian and non-abelian models of mass generation.

Superbranes

We consider the doubly supersymmetric formulation of various p-branes, that is, we replace the worldsurface of a super p-brane by a super worldsurface and consider the embedding of the latter into a target superspace. The number of worldsurface fermionic coordinates is taken to be half as many as those of the target superspace. We show that a simple geometrical constraint and its integrability condition lead to manifestly worldsurface supersymmetric field equations for a large class of super p-branes. We illustrate this procedure in some detail in the case of the D = 11 superfivebrane. We also describe a class of super p-branes in which a worldsurface linear supermultiplet arises. In some cases we show that an additional constraint involving the curvature of an appropriate worldsurface antisymmetric tensor potential is needed to put the theory on-shell.

String cosmology with a time-dependent antisymmetric tensor potential.

We present a class of exact solutions for homogeneous, anisotropic cosmologies in four dimensions derived from the low-energy string effective action including a homogeneous dilaton $\phi$ and antisymmetric tensor potential $B_{\mu\nu}$. Making this potential time-dependent produces an anisotropic energy-momentum tensor, and leads us to consider a Bianchi I cosmology. The solution for the axion field must then only be a linear function of one spatial coordinate. This in turn places an upper bound on the product of the two scale factors evolving perpendicular to the gradient of the axion field. The only late-time isotropic solution is then a {\em contracting} universe.

CONSTRAINED DYNAMICS OF THE COUPLED ABELIAN TWO-FORM

I present the reduction of phase space of the theory of an antisymmetric tensor potential coupled to an Abelian gauge field, using Dirac's procedure. Duality transformations on the reduced phase space are also discussed.

Topological charges and central changes in 3 + 1 dimensional supersymmetry

We show that supersymmetric theories in 3+1 dimensions which have a topological charge generically have an extended N=2 supersymmetry algebra with two real central charges (the maximum number possible). One central charge is the topological charge. The other central charge arises due to the presence of an extra conserved current in the supermultiplet of the antisymmetric tensor potential for the topological current.

Kaluza-Klein origin for the superstring tension.

The natural configuration space of a string in a background antisymmetric tensor potential is not loop space, but a principal U(1) bundle over loop space. This allows a Kaluza-Klein--like interpretation of the string tension as momentum along the U(1) fiber, and a similar interpretation is possible for a {ital p}-dimensional object. The higher-dimensional'' action incorporating this momentum as a dynamical variable is given for a {ital p}-dimensional supersymmetric extended object, in a general supergravity background. Its relevance, for a flat background, to classical anomalies'' in the supersymmetry algebra is explained.

The cosmological constant is possibly zero, but the proof is probably wrong

Substituting a field configuration into an action and varying that action is not equivalent to substituting the configuration into the field equations. Consequently the cosmological constant measured experimentally is not in general given by the coefficient of √−g in some effective action but rather by the coefficient of gμν in the effective Einstein equations. In the case of a rank-three antisymmetric tensor potential, for example, these two quantities differ by a sign. This invalidates Hawking's proof that the cosmological constant is probably zero, and casts doubt on similar attempts based on maximizing the exponential of minus the euclidean action.

Minimal N = 2 supergravity in superspace

A systematic derivation of a new minimal N = 2 supergravity multiplet with 32+32 degrees of freedom is given. The physical fields are one graviton, two gravitinos, one photon, and a vector multiplet where the pseudoscalar is replaced by an antisymmetric tensor. One of the auxiliary fields is the gauge field of a local SO(2) symmetry. On-shell this multiplet describes the truncation of a N = 4 supergravity theory with an antisymmetric tensor potential.

Statics for the antisymmetric tensor potential due to closed strings

We study the properties, in the static limit of the antisymmetric tensor field, introduced by Kalb and Ramond to describe string interactions. Explicit expressions are obtained for a closed, circular string. These solutions indicate the lack of a monopole source. The coupling between two circular strings is calculated, leading to the hypothesis of a « sense » for closed strings.