The M5-brane on K3 x T^2

We discuss the low energy effective theory of an M5-brane wrapped on a smooth holomorphic four-cycle of K3 x T^2, including the special case of T^6. In particular we give the lowest order equations of motion and resolve a puzzle concerning the counting of massless modes that was reported in hep-th/9906094. In order to find agreement with black hole entropy and anomaly inflow arguments we propose that some of the moduli become massive.Comment: 17 pages LaTex, reference adde

Heterotic M2-branes

We construct the action for N M2-branes on $S^1/{Z}_2$. The resulting theory has a gauge anomaly but this can be cancelled if the two fixed point planes each support 8 chiral Fermions in the fundamental of U(N). Taking the low energy limit leads to the worldsheet theory of N free heterotic strings whose quantization induces an $E_8$ spacetime gauge symmetry on each fixed point plane. Thus this paper presents a non-abelian worldvolume analogue of the classic Horava-Witten analysis.Comment: reference adde

Calibrations, Monopoles and Fuzzy Funnels

We present new non-Abelian solitonic configurations in the low energy effective theory describing a collection of N parallel D1--branes. These configurations preserve 1/4, 1/8, 1/16 and 1/32 of the spacetime supersymmetry. They are solutions to a set of generalised Nahm's equations which are related to self-duality equations in eight dimensions. Our solutions represent D1--branes which expand into fuzzy funnel configurations ending on collections of intersecting D3--branes. Supersymmetry dictates that such intersecting D3--branes must lie on a calibrated three-surface of spacetime and we argue that the generalised Nahm's equations encode the data for the construction of magnetic monopoles on the relevant three-surfaces.Comment: 19 pages. Latex. v2: added references and acknowledgmen

Null Reductions of M5-Branes

We perform a general reduction of an M5-brane on a spacetime that admits a null Killing vector, including couplings to background 4-form fluxes and possible twisting of the normal bundle. We give the non-abelian extension of this action and present its supersymmetry transformations. The result is a class of supersymmetric non-lorentzian gauge theories in 4+1 dimensions, which depend on the geometry of the six-dimensional spacetime. These can be used for DLCQ constructions of M5-branes reduced on various manifolds.Comment: 21 pages; more typos corrected and additional comment in the introduction, to appear in JHEP (hopefully

Non-Lorentzian Field Theories with Maximal Supersymmetry and Moduli Space Dynamics

We present gauge theories in 2+1 and 4+1 dimensions with 16 supersymmetries which are invariant under rotations and translations but not boosts. The on-shell conditions reduce the dynamics to motion on a moduli space of BPS states graded by a topologically conserved quantity. On each component of the moduli space only half the supersymmetry is realised. We argue that these theories describe M2-branes and M5-branes which have been infinitely boosted so that their worldvolume `time' has become null.Comment: Minor corrections including an extra term in the susy variation of G_{ij

Flux and Freund-Rubin Superpotentials in M-theory

We discuss the effective action for weak G_2 compactifications of M-theory. The presence of fluxes acts as a source for the the axions and drives the Freund-Rubin parameter to zero. The result is a stable non-supersymmetric vacuum with a negative cosmological constant. We also give the superpotential which generates the effective potential and discuss a simple model which aims to incorporate the effects of supersymmetry breaking by the gauge sector.Comment: Discussion of KK-scale and cosmological scales revise

Enhanced Coset Symmetries and Higher Derivative Corrections

After dimensional reduction to three dimensions, the lowest order effective actions for pure gravity, M-theory and the Bosonic string admit an enhanced symmetry group. In this paper we initiate study of how this enhancement is affected by the inclusion of higher derivative terms. In particular we show that the coefficients of the scalar fields associated to the Cartan subalgebra are given by weights of the enhanced symmetry group.Comment: 37 pages Latex. Reference added and other minor correction

Duality Groups, Automorphic Forms and Higher Derivative Corrections

We study the higher derivative corrections that occur in type II superstring theories in ten dimensions or less. Assuming invariance under a discrete duality group G(Z) we show that the generic functions of the scalar fields that occur can be identified with automorphic forms. We then give a systematic method to construct automorphic forms from a given group G(Z) together with a chosen subgroup H and a linear representation of G(Z). This construction is based on the theory of non-linear realizations and we find that the automorphic forms contain the weights of G. We also carry out the dimensional reduction of the generic higher derivative corrections of the IIB theory to three dimensions and find that the weights of E_8 occur generalizing previous results of the authors on M-theory. Since the automorphic forms of this theory contain the weights of E_8 we can interpret the occurrence of weights in the dimensional reduction as evidence for an underlying U-duality symmetry.Comment: Typos corrected and a reference adde

Perturbation Theory From Automorphic Forms

Using our previous construction of Eisenstein-like automorphic forms we derive formulae for the perturbative and non-perturbative parts for any group and representation. The result is written in terms of the weights of the representation and the derivation is largely group theoretical. Specialising to the E_{n+1} groups relevant to type II string theory and the representation associated with node n+1 of the E_{n+1} Dynkin diagram we explicitly find the perturbative part in terms of String Theory variables, such as the string coupling g_d and volume V_n. For dimensions seven and higher we find that the perturbation theory involves only two terms. In six dimensions we construct the SO(5,5) automorphic form using the vector representation. Although these automorphic forms are generally compatible with String Theory, the one relevant to R^4 involves terms with g_d^{-6} and so is problematic. We then study a constrained SO(5,5) automorphic form, obtained by summing over null vectors, and compute its perturbative part. We find that it is consistent with String Theory and makes precise predictions for the perturbative results. We also study the unconstrained automorphic forms for E_6 in the 27 representation and E_7 in the 133 representation, giving their perturbative part and commenting on their role in String Theory.Comment: Typos fixed and other minor corrections. A 'note added' include

Non-Abelian Field Theory of stable non-BPS Branes

We derive the action for the non-abelian field theory living on parallel non-BPS D3-branes in type IIA theory on the orbifold T^4/I_4(-1)^F_L. The classical moduli space for the massless scalars originating in the ``would be'' tachyonic sector shows an interesting structure. In particular, it contains non-abelian flat directions. At a generic point in this branch of the moduli space the scalars corresponding to the the separations of the branes acquire masses and the branes condense. Although these tree level flat directions are removed by quantum corrections we argue that within the loop approximation the branes still condense.Comment: 1 reference adde