The theme of this thesis is the study of field theories generically without Lorentz symmetry, but possessing an inhomogeneous scaling symmetry. A number of aspects of such models are explored, including the addition of supersymmetry, and their application in the construction of more conventional conformal field theories.
In Part I, we describe a scaling technique by which non-Lorentzian theories with an inhomogeneous scaling symmetry are obtained from Lorentzian supersymmetric models, while retaining all supersymmetry of the parent theory. The dynamics of the resulting theories are generically constrained to the moduli space of some BPS soliton. We explore this scaling technique and the resulting reduction to superconformal quantum mechanics for some examples, including several relevant to the branes of M-theory.
In Part II, we build from the ground up the theory of models in five dimensions with an exotic $SU(1,3)$ spacetime symmetry, including an inhomogeneous scaling. We derive and solve the corresponding Ward-Takahashi identities for correlators, and demonstrate how such models naturally describe any six-dimensional conformal field theory on a conformal compactification of Minkowski space. We derive necessary conditions for a generic $SU(1,3)$ theory to admit such a six-dimensional interpretation, and also explore a degenerate limit of the construction that recovers the standard DLCQ picture. Finally, we study in detail an explicit $SU(1,3)$ model, conjectured to provide a Lagrangian description of the non-Abelian $(2,0)$ theory. The theory is shown to realise six-dimensional physics through the inclusion of singular points carrying non-zero instanton charge, which are encoded by instanton operators in the path integral. We explore the constrained dynamics of the theory, which are shown to describe the propagation of Yang-Mills instanton-particles between such points.
Lorentzian signature D-branes of all dimensions for the Nappi-Witten string are constructed. This is done by rewriting the gluing condition $J_+=FJ_-$ for the model chiral currents on the brane as a well posed first order differential problem and by solving it for Lie algebra isometries $F$ other than Lie algebra automorphisms. By construction, these D-branes are not twined conjugacy classes. Metrically degenerate D-branes are also obtained.
We study D-branes in the Lorentzian signature 2D black hole string theory. We use the technique of gauged WZW models to construct the associated boundary conformal field theories. The main focus of this work is to discuss the (semi-classical) world-volume geometries of the D-branes. We also discuss comparison of our work with results in related gauged WZW models.
We study the exact construction of D-branes in Lorentzian AdS(3). We start by defining a family of conformal field theories that gives a natural Euclidean version of the SL(2,R) CFT and does not correspond to H(3)+, the analytic continuation of AdS(3). We argue that one can recuperate the exact CFT results of Lorentzian AdS(3), upon an analytic continuation in the moduli space of these conformal field theories. Then we construct exact boundary states for various symmetric and symmetry-breaking D-branes in AdS(3).
We consider string theory on the Lorentzian Melvin geometry, which is obtained by analytically continuing the two-parameter Euclidean Melvin background. Because this model provides a solvable conformal field theory that describes time-dependent twisted string dynamics, we study the string one-loop partition function and the D-brane spectrum. We found that both the wrapping D2-brane and the codimension-one D-string emit winding strings, and this behavior can be traced to the modified open string Hamiltonian on these probe D-branes.
We show that the Bagger-Lambert-Gustavsson (BLG) theory with two pairs of negative norm generators is derived from the scaling limit of an orbifolded Aharony-Bergman-Jafferis-Maldacena (ABJM) theory. The BLG theory with many Lorentzian pairs is known to be reduced to the Dp-brane theory via Higgs mechanism, so our scaling procedure can be used to derive Dp-branes directly from M2-branes in the field theory language. In this paper, we focus on the D3-brane case and investigate the scaling limits of various quiver Chern-Simons theories obtained from different orbifolding actions. Remarkably, in …
M-theory on $AdS_7 \times S^4$ admits a description where the $AdS_7$ factor is constructed as a timelike Hopf fibration over a non-compact three dimensional complex projective space $\tilde{\mathbb{CP}}^3$. We consider the worldvolume theory for M5-branes at a fixed $\tilde{\mathbb{CP}}^3$ radius which, after reduction along the timelike fibre, is given by an $Ω$-deformed Yang-Mills theory with eight supercharges. Taking the radius to infinity then induces a classical RG flow. We construct the fixed point action which has an enhanced 24 supercharges and which can be understood as the $(2,0)$ …
Recently, a class of non-Lorentzian supersymmetric Lagrangian field theories was considered, in some cases describing M-theory brane configurations, but more generally found as fixed points of non-Lorentzian RG flows induced upon Lorentzian theories. In this paper, we demonstrate how the dynamics of such theories can be reduced to motion on the supersymmetric moduli space of BPS solitons of the parent theory. We focus first on the $\mathcal{N}=(1,1)$ $σ$-model in $(1+1)$-dimensions with potential, where we produce a supersymmetric extension to the standard geodesic approximation for slow kink …
We show that by adding a supersymmetric Faddeev-Popov ghost sector to the recently constructed Bagger-Lambert theory based on a Lorentzian three algebra, we obtain an action with a BRST symmetry that can be used to demonstrate the absence of negative norm states in the physical Hilbert space. We show that the combined theory, expanded about its trivial vacuum, is BRST equivalent to a trivial theory, while the theory with a vev for one of the scalars associated with a null direction in the three-algebra is equivalent to a reformulation of maximally supersymmetric 2+1 dimensional Yang-Mills theo…
The boundary states for AdS_2 D-branes in Lorentzian AdS_3 space-time are presented. AdS_2 D-branes are algebraically defined by twisted Dirichlet boundary conditions and are located on twisted conjugacy classes of SL(2,R). Using free field representation of symmetry currents in the SL(2,R) WZNW model, the twisted Dirichlet gluing conditions among currents are translated to matching conditions among free fields and then to boundary conditions among the modes of free fields. The Ishibashi states are written as coherent states on AdS_3 in the free field formalism and it is shown that twisted Dir…
We study Lorentzian D-particles in linear dilaton and the two dimensional black hole backgrounds. The D-particle trajectory follows an accelerated trajectory which is smeared by stringy corrections. For the black hole background we find that the portion of the trajectory behind the horizon appears to an asymptotic observer as ghost D-particle. This suggests a way of constructing a matrix model for the Lorentzian black hole background.
We analyze the coulomb branch of the non-unitary Lorentzian three algebra theory that has been proposed as a possible candidate for describing the world volume theory of multiple M2-branes. In order that it describes the theory of multiple M2-branes in flat eleven dimensional space-time, the ghost fields must decouple and the physical theory must be independent of the eight coordinates of the moduli space representing the center of mass coordinates of the branes. We show that the structure of the Coulomb branch is consistent with this requirement. While the full moduli space has the structure …
We consider superconformal and supersymmetric field theories on four-dimensional Lorentzian curved space-times, and their five-dimensional holographic duals. As in the Euclidean signature case, preserved supersymmetry for a superconformal theory is equivalent to the existence of a charged conformal Killing spinor. Differently from the Euclidean case, we show that the existence of such spinors is equivalent to the existence of a null conformal Killing vector. For a supersymmetric field theory with an R-symmetry, this vector field is further restricted to be Killing. We demonstrate how these res…
We investigate the supersymmetric index of N=2,3 SU(n) supersymmetric Yang-Mills Chern Simons theories at level k by using the brane configuration with a (p,q)5-brane. We can explain that the supersymmetry breaking occurs when k<n in terms of the s-rule for Type IIB branes. The supersymmetric index coincides with the number of the possible supersymmetric brane configurations. We also discuss a construction of a family of theories which have the same supersymmetric index.
We consider both the supersymmetric open 2-brane and bosonic open 2-brane, their quantization and spectrum under the flat metric condition. The supersymmetric spectrum turns out to be discrete, while the spectrum of purely bosonic open 2-brane is shown to be devoid of any massless states.
We describe a general process where a non-Lorentzian rescaling of a supersymmetric field theory leads to a scale-invariant fixed point action without Lorentz invariance but where the supersymmetry is preserved or even enhanced. We apply this procedure to five-dimensional maximally supersymmetric super-Yang-Mills, leading to a field theory with 24 super(conformal) symmetries. We also apply this procedure to the BLG model with 32 super(conformal) symmetries and ABJM models with 24 super(conformal) symmetries.
We study aspects of the interaction between a D-brane and an anti-D-brane in the maximally supersymmetric plane wave background of type IIB superstring theory, which is equipped with a mass parameter mu. An early such study in flat spacetime (mu=0) served to sharpen intuition about D-brane interactions, showing in particular the key role of the ``stringy halo'' that surrounds a D-brane. The halo marks the edge of the region within which tachyon condensation occurs, opening a gateway to new non-trivial vacua of the theory. It seems pertinent to study the fate of the halo for non--zero mu. We fo…
We extend the study on D-branes in the type IIB plane wave background to less supersymmetric configurations. We show that many new supersymmetric D-branes can be found by turning on electric as well as magnetic background fluxes, or constantly boosting D-branes.
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.
We examine if there exists a zero-energy supersymmetric ground state for the fundamental five-brane. Looking for an $SO(6)\times SO(2)$- invariant ground state, we construct, in the light-cone gauge, perturbatively a Nicolai map up to third order in the inverse five-brane tension. We show that the Nicolai map equilibrates and the five-brane has a zero-energy normalizable supersymmetric vacuum state. For the other p-branes, we argue that only the three-brane has a zero-energy ground state.
We propose a generic supersymmetric and kappa-invariant action for describing coincident D0-branes with non-abelian matter fields on their worldline. The action is shown to be in agreement with the Matrix Theory limit of the ND0-brane effective action.
Using N=2 off-shell supergravity in five dimensions, we supersymmetrize the brane world scenario of Randall and Sundrum. We extend their construction to include supersymmetric matter at the fixpoints.
In certain regions of the moduli space of K3 and Calabi-Yau manifolds, D-branes wrapped on non-supersymmetric cycles may give rise to stable configurations. We show that in the orbifold limit, some of these stable configurations can be described by solvable boundary conformal field theories. The world-volume theory of N coincident branes of this type is described by a non-supersymmetric U(N) gauge theory. At the boundary of the region of stability, there are marginal deformations connecting the non-supersymmetric brane to a pair of D-branes wrapped on supersymmetric cycles. We also discuss var…
We refine a previous proposal for obtaining the multi-instanton partition function from the supersymmetric index of the 1d supersymmetric gauge theory on the worldline of D0-branes. We provide examples where the refinements are crucial for obtaining the correct result.
We derive superalgebras in many types of supersymmetric M-brane backgrounds. The backgrounds examined here include the cases of the M-wave and the M-Kaluza-Klein monopole. On the basis of the obtained algebras, we deduce all the supersymmetric non-orthogonal intersections of the M-Kaluza-Klein monopole and the M-5-brane at angles. In addition, we present a 1/4 supersymmetric worldvolume 3-brane soliton on the M-5-brane in the M-5-brane background as an extended solution of the 3-brane solitons of the M-5-brane by Howe, Lambert and West. This soliton can be interpreted as a certain intersection…
Leinweber Institute for Theoretical Physics and Department of Physics, University of California, Berkeley（加州大学伯克利分校莱因韦伯理论物理研究所和物理系）；Center of Gravity, The Niels Bohr Institute, Copenhagen University（哥本哈根大学尼尔斯玻尔研究所引力中心）；Nordita, KTH Royal Institute of Technology and Stockholm University（诺迪塔，皇家理工学院和斯德哥尔摩大学）；Department of Engineering Sciences, Istanbul University-Cerrahpaşa（伊斯坦布尔大学-杰拉帕萨工程学院）
We employ generalized complex geometry to investigate supersymmetric embeddings of D-brane probes in a large class of SU(2) structure manifolds. This class includes the gravity dual of mass deformation and marginal beta deformation of N=4 SYM gauge theory. We find supersymmetric configurations of D-branes with different dimensionality and propose their interpretation in the dual gauge theory.
We study supersymmetric intersections of M2 and M5 branes with different pp-waves of M-theory. We consider first M-brane probes in the background of pp-waves and determine under which conditions the embedding is supersymmetric. We particularize our formalism to the case of pp-waves with 32, 24 and 20 supersymmetries. We also construct supergravity solutions for the brane-wave system. Generically these solutions are delocalised along some directions transverse to the brane and preserve the same number of supersymmetries as in the brane probe approach.
We construct a class of Lie 3-algebras with an arbitrary number of pairs of generators with Lorentzian signature metric. Some examples are given and corresponding BLG models are studied. We show that such a system in general describes a supersymmetric massive vector multiplets after the ghost fields are Higgsed. Simple systems with nontrivial interaction are realized by infinite dimensional Lie 3-algebras associated with the loop algebras. The massive fields are then naturally identified with the Kaluza-Klein modes by the toroidal compactification triggered by the ghost fields. For example, Dp…
In the orbifold limit of K3, one can give exact conformal field theory description of D-branes wrapped on certain non-supersymmetric cycles of K3. We study the effect of switching on the `non-geometric blow up modes' corresponding to anti-symmetric tensor gauge field flux through the 2-cycles on these D-branes. Working to first order in the blow up parameter, we determine the region of the moduli space in which these D-branes are stable. Across the boundary of this region, the D-brane wrapped on the non-supersymmetric cycle decays to a pair of D-branes, each wrapped on a supersymmetric cycle, …
We use dyonic brane configurations of type 0 string theory to study large N non-supersymmetric 4d gauge theories. The brane configurations define theories similar to the supersymmetric ones which arise in type II. We find the non-SUSY analogues of N=2 and N=1. In particular we suggest new non-SUSY CFT's and a brane realization of a non-SUSY Seiberg duality.
We study the correspondence between the moduli space of vacua of three-dimensional supersymmetric Yang-Mills (Maxwell) Chern-Simons theories and brane configurations with (p,q)5-brane. For Coulomb branches, the number of the massless adjoint scalar fields in various supersymmetric theories exactly coincides with the number of the freely moving directions of D3-branes stretched between two 5-branes. When we include a matter superfield into the supersymmetric Chern-Simons theory two distinct symmetric and asymmetric phase appear. The symmetric phase is peculiar to this Chern-Simons Higgs system.…
Generalizing the work by Cherkis and Schwarz [1], we carry out the double dimensional reduction of supersymmetric M5 brane on K3 to obtain the supersymmetric action of heterotic string in 7-dimensional flat space-time. Motivated by this result, we propose the supersymmetric heterotic action in 10-dimensional flat space-time where the current algebra is realized in a novel way. We explicitly verify the kappa-symmetry of the proposed action.
We systematically analyze supersymmetric D-branes in the type IIB plane wave background using Green-Schwarz superstring theory. We find several new supersymmetric oblique and curved D-branes. The supersymmetries preserved by various configurations of these D-branes including their intersections are also identified. In particular, we show that $D_+$-branes of type (+,-,n,n) for n=1,2,3,4 preserve 4 dynamical supersymmetries by introducing gauge field excitations and newly discovered oblique D5- and D7-branes also preserve four or two dynamical supersymmetries with gauge field condensates. Furth…
We study non-supersymmetric SO(3)-invariant deformations of d=3, N=8 super Yang-Mills theory and their type IIA string theory dual. By adding both gaugino mass and scalar mass, dielectric D4-brane potential coincides with D5-brane potential in type IIB theory. We find the region of parameter space where the non-supersymmetric vacuum is described by stable dielectric NS5-branes. By considering the generalized action for NS5-branes in the presence of D4-flux, we also analyze the properties of dielectric NS5-branes.
A supersymmetric action functional describing the interaction of the fundamental superstring with the D=10, type IIB Dirichlet super-9-brane is presented. A set of supersymmetric equations for the coupled system is obtained from the action principle. It is found that the interaction of the string endpoints with the super-D9-brane gauge field requires some restrictions for the image of the gauge field strength. When those restrictions are not imposed, the equations imply the absence of the endpoints, and the equations coincide either with the ones of the free super-D9-brane or with the ones for…
We present two classes of regular supergravity backgrounds dual to supersymmetric and non-supersymmetric gauge theories living on the world-volume of wrapped branes. In particular we consider the Maldacena Nunez and the Klebanov Strassler models, describing N=1 and N=2 theories, and find their non supersymmetric generalization by explicitly solving the second order equation of motion. We also study various aspects of these solutions, including the supersymmetry breaking issue and the vacuum energy.
We study D-branes of N=2 supersymmetric sigma models. Supersymmetric nonlinear sigma models with 2-dimensional target space have D0,D1,D2-branes, which are realized as A-,B-type supersymmetric boundary conditions on the worldsheet. When we embed the models in the string theory, the Kahler potential is restricted and leads to a 2-dim black hole metric with a dilaton background. The D-branes in this model are susy cycles and consistent with the analysis of conjugacy classes. The generalized metrics with U(n) isometry is proposed and dynamics on them are realized by linear sigma models. We invest…
A class of p-brane solutions for supersymmetric gravity theories with negative cosmological constant are proposed and analyzed. The solutions are purely bosonic and contain a worldsheet and a transverse section. The classification relays on the number of intrinsic Killing spinors on the worldsheet and the transverse section. A explicit discussion of the classification is performed for the four dimensional worldsheet case.
We construct a class of supersymmetric boundary interactions in N=2 field theories on the half-space, which depend on parameters that are not at all renormalized or not renormalized in perturbation theory beyond one-loop. This can be used to study D-branes wrapped on a certain class of Lagrangian submanifolds as well as holomorphic cycles. The construction of holomorphic D-branes is in close relationship with the background independent open string field theory approach to brane/anti-brane systems. As an application, mirror pairs of Lagrangian and holomorphic D-branes are identified. The mirror…
We study webs of D3- and D5-branes in type IIB supergravity. These webs preserve at least 8 supercharges. By solving the Killing spinor equations we determine the form of supergravity solutions for the system. We then turn to the sub-class of the intersecting D3/D5 brane system and elucidate some of its features.
In this paper we investigate the form of calibrated M5-branes in the presence of a nonvanishing 3-form field H. We discuss the influence of the H-field on the deformation of supersymmetric n-cycles (in particular SLAG submanifolds in R^n). In addition we argue for a construction which relates calibrated M5-branes of different curved dimensions to each other.
We find a class of flat supersymmetric brane-antibrane configurations. They follow from ordinary brane-antibrane systems by turning on a specific worldvolume background electric field, which corresponds to dissolved fundamental strings. We have clarified in detail how they arise and identified their constituent charges as well as the corresponding supergravity solutions. Adopting the matrix theory description, we construct the worldvolume gauge theories and prove the absence of any tachyonic degrees. We also study supersymmetric solitons of the worldvolume theories.
We construct non-supersymmetric four dimensional gauge theories arising as effective theories of D-branes placed on various singularities in Type 0B string theory. We mostly focus on models which are conformal in the large N limit and present both examples appearing on self-dual D3-branes on orbifold singularities and examples including orientifold planes. Moreover, we derive type 0 Hanany-Witten setups with NS 5-branes intersected by D-branes and the corresponding rules for determining the massless spectra. Finally, we discuss possible duality symmetries (Seiberg-duality) for non-supersymmetr…
We derive an energy bound for a `baryonic' D5-brane probe in the $adS_5\times S^5$ background near the horizon of $N$ D3-branes. Configurations saturating the bound are shown to be 1/4 supersymmetric $S^5$-wrapped D5-branes, with a total Born-Infeld charge $N$. Previous results are recovered as a special case. We derive a similar energy bound for a `baryonic' M5-brane probe in the background of $N$ M5-branes. Configurations saturating the bound are again 1/4 supersymmetric and, in the $adS_7\times S^4$ near-horizon limit, provide a worldvolume realization of the `baryon string' vertex of the (…
In the last few years, brane tilings have proven to be an efficient and convenient way of studying supersymmetric gauge theories living on D3-branes or M2-branes. In these pages we present a quick and simple introduction to the subject, hoping this could tickle the reader's curiosity to learn more on this extremely fascinating subject.
We consider supersymmetric extensions of a recently proposed partonic description of a bosonic p-brane which reformulates the Nambu-Goto action as an interacting multi-particle action with Filippov-Lie algebra gauge symmetry. We construct a worldline supersymmetric action by postulating, among others, a p-form fermion. Demanding a local worldline supersymmetry rather than the full worldvolume supersymmetry, we circumvent a known no-go theorem against the construction of a Ramond-Neveu-Schwarz supersymmetric action for a p-brane of p>1. We also derive a spacetime supersymmetric Green-Schwarz ex…
We study the supersymmetric properties of D7-branes in the warped deformed conifold. We consider the $κ$-symmetry conditions on D7-branes in this specific warped background, taking into account the background NS-NS 2-form flux. While any holomorphic embedding defines a supersymmetric D7-brane in the absence of background H-flux, most of the D7-brane embeddings considered in the literature do not preserve supersymmetry for the warped deformed conifold without also including brane worldvolume flux. For the simplest such embedding, we construct numerically the worldvolume fluxnecessary to restore…
We consider a supersymmetric extension of the SL(2;Z)-covariant D3-brane action proposed by Nurmagambetov, and prove its kappa-symmetry in an on-shell type-IIB supergravity background.
We derive level-rank duality in pure Chern-Simons gauge theories from a non-supersymmetric Seiberg duality by using a non-supersymmetric brane configuration in type IIB string theory. The brane configuration consists of fivebranes, N D3 antibranes and an O3 plane. By swapping the fivebranes we derive a 3d non-supersymmetric Seiberg duality. After level shifts from loop effects, this identifies the IR of Sp(2N)_{2k-2N+2} and Sp(2k-2N+2)_{-2N} pure Chern-Simons theories, which is a level-rank pair. We also derive level-rank duality in a Chern-Simons theory based on a unitary group.
We discuss how to incorporate non-supersymmetric branes in compactifications of type II string theories. We particularly focus on flux compactifications on $SU(3)\times SU(3)$ structure manifolds to four dimensions, so that a linear $\mathcal{N}=1$ supersymmetry is spontaneously broken by spacetime filling Dp-branes. Anti-Dp-branes are a very special subset of such branes but our analysis is generic. We show that the backreaction of non-supersymmetric branes can be incorporated into the standard 4d $\mathcal{N}=1$ supergravity by including a nilpotent chiral multiplet. Supersymmetry in such se…
For a given attractor black hole with generic D6-D4-D2-D0-charges in four dimensions we identify the set of supersymmetric branes, static or stationary in global coordinates, of the corresponding eleven-dimensional near horizon geometry. The set of these BPS states, which includes branes which partially or fully wrap the horizon, should play a role in understanding the partition function of black holes with D6-charges.
A recent study of filtered deformations of (graded subalgebras of) the minimal five-dimensional Poincaré superalgebra resulted in two classes of maximally supersymmetric spacetimes. One class are the well-known maximally supersymmetric backgrounds of minimal five-dimensional supergravity, whereas the other class does not seem to be related to supergravity. This paper is a study of the Kaluza--Klein reductions to four dimensions of this latter class of maximally supersymmetric spacetimes. We classify the lorentzian and riemannian Kaluza--Klein reductions of these backgrounds, determine the frac…
We study wrapped brane configurations via possible maximally supersymmetric gauged supergravities. First, we construct various supersymmetric wrapped D3 brane configurations from D=5 N=8 SO(6) gauged supergravity. This procedure provides certain new examples of wrapped D3 branes around supersymmetric cycles inside non-compact special holonomy manifolds. We analyze their behaviors numerically in order to discuss a correspondence to Higgs and Coulomb branches of sigma models on wrapped D3 branes. We also realize supersymmetric wrapped M2 branes from D=4 N=8 SO(8) gauged supergravity. Then, we st…
We study the vacuum polarization of supersymmetric toroidal D-brane placed in the constant electromagnetic field. Explicit calculation of the one-loop effective potential is performed for membrane with constant magnetic or electric background. We find the one-loop potentials vanish as the effect of supersymmetry,
We find various supersymmetric configurations of toroidal M2 brane solutions in $\AdS_4 \times S^7$ or, more generally, in $\AdS_4 \times S^7/Z_k$. In this class we identify solutions preserving 1/4 and 1/8 supersymmetries of the background. The supersymmetric M2 branes have angular momenta and winding on $S^7$, and null world-volumes. In certain cases they collapse to string-like configurations. These configurations can be viewed as a higher-dimensional (membrane) analog of BMN states. We compute the energy and angular momenta, showing that all supersymmetric configurations obey the BPS relat…
We review the salient features of spacetime and worldvolume supersymmetric super p-brane actions. These are sigma models for maps from a worldvolume superspace to the target superspace. For p-branes, the symmetries of the model depend crucially on the existence of closed super (p+1)-forms on a worldvolume superspace, built out of the pull-backs of the Kalb-Ramond super (p+1)-form in target superspace and its curvature. This formulation of super p-branes is usually referred to as the twistor-like formulation.
We obtain new examples of partially supersymmetric M-brane solutions defined on products of Ricci-flat manifolds, which contain two-dimensional Lorentzian submanifold R^{1,1}_{*}/Z_2 with one parallel spinor. The examples belong to the following configurations: M2, M5, M2-M5 and M5-M5. Among them a M2 solution with N =1/32 fractional number of preserved supersymmetries is presented. The examples with three M-branes were considered earlier in our paper with A.A. Golubtsova.
We construct type II A brane configuration of N=(4,4) supersymmetric two dimensional gauge theory with gauge group U(1) and N_f hypermultiplets in the fundamental representation. By lifting to M-theory (strong coupling), we can see the origin of the R-symmetry enhancement of the Coulomb branch. One can also find two theories which become equivalent at strong coupling.
