Olaf Lechtenfeld

On the N=2 Supersymmetric Camassa-Holm and Hunter-Saxton Equations (2008)

N=4 superconformal n-particle quantum mechanics on the real line is governed by two prepotentials, U and F, which obey a system of partial nonlinear differential equations generalizing the...

Lenells, Jonatan, Lechtenfeld, Olaf

We consider N=2 supersymmetric extensions of the Camassa-Holm and Hunter-Saxton equations. We show that they admit geometric interpretations as Euler equations on the superconformal algebra of...

SU(3)-Equivariant Quiver Gauge Theories and Nonabelian Vortices (2008)

Lechtenfeld, Olaf, Popov, Alexander Df, Szabo, Richard J

We consider SU(3)-equivariant dimensional reduction of Yang-Mills theory on Kaehler manifolds of the form M x SU(3)/H, with H = SU(2) x U(1) or H = U(1) x U(1). The induced rank two quiver gauge...

SU(3)-Equivariant Quiver Gauge Theories and Nonabelian Vortices (2008)

Lechtenfeld, Olaf, Popov, Alexander D., Szabo, Richard J.

We consider SU(3)-equivariant dimensional reduction of Yang-Mills theory on Kaehler manifolds of the form M x SU(3)/H, with H = SU(2) x U(1) or H = U(1) x U(1). The induced rank two quiver gauge...

Yang-Mills Instantons and Dyons on Group Manifolds (2008)

WDVV solutions from orthocentric polytopes and Veselov systems (2008)

We consider Euclidean SU(N) Yang-Mills theory on the space GxR, where G is a compact semisimple Lie group, and introduce first-order BPS-type equations which imply the full Yang-Mills equations. For...

Non-anticommutative solitons (2008)

N=4 superconformal n-particle quantum mechanics on the real line is governed by two prepotentials, U and F, which obey a system of partial nonlinear differential equations generalizing the...

Ketov, Sergei V, Lechtenfeld, Olaf

Certain supersymmetric sigma models in 2+1 dimensions feature multi-soliton solutions, with and without scattering. We subject these systems to a non-anticommutative deformation by replacing the...

Non-anticommutative solitons (2008)

Ketov, Sergei V., Lechtenfeld, Olaf

Certain supersymmetric sigma models in 2+1 dimensions feature multi-soliton solutions, with and without scattering. We subject these systems to a non-anticommutative deformation by replacing the...

N=4 mechanics, WDVV equations and roots (2008)

Galajinsky, Anton, Lechtenfeld, Olaf, Polovnikov, Kirill

N=4 superconformal n-particle quantum mechanics on the real line is governed by two prepotentials, U and F, which obey a system of partial nonlinear differential equations generalizing the...

N=4 mechanics, WDVV equations and roots (2008)

Galajinsky, Anton, Lechtenfeld, Olaf, Polovnikov, Kirill

N=4 superconformal multi-particle quantum mechanics on the real line is governed by two prepotentials, U and F, which obey a system of partial differential equations linear in U and generalizing the...

References (2007)

J. Louis, H. Nicolai (eds, Phys Lett B, G. Chalmers, Nucl Phys B, ...

[55] K. Junemann, O. Lechtenfeld and A.D. Popov, hep-th/9901164 Non-local symmetries of the closed N=2 string, Nucl. Phys. B548 (1999) 449-474. [56] A. Galajinsky and O. Lechtenfeld, hep-th/9903149...

Noncommutative Solitons (2007)

Noncommutative Solitons (2007)

Solitonic objects play a central role in gauge and string theory (as, e.g., monopoles, black holes, D-branes, etc.). Certain string backgrounds produce a noncommutative deformation of the low-energy...

Scattering of Noncommutative Waves and Solitons in a Supersymmetric Chiral Model in 2+1 Dimensions (2007)

Solitonic objects play a central role in gauge and string theory (as, e.g., monopoles, black holes, D-branes, etc.). Certain string backgrounds produce a noncommutative deformation of the low-energy...

Gutschwager, Christian, Ivanova, Tatiana A., Lechtenfeld, Olaf

Interactions of noncommutative waves and solitons in 2+1 dimensions can be analyzed exactly for a supersymmetric and integrable U(n) chiral model extending the Ward model. Using the Moyal-deformed...

Quantum Aspects of the Noncommutative Sine-Gordon Model (2007)

Kurkcuoglu, Seckin, Lechtenfeld, Olaf

In this paper, we first use semi-classical methods to study quantum field theoretical aspects of the integrable noncommutative sine-Gordon model proposed in [hep-th/0406065]. In particular, we...

N=4 superconformal Calogero models (2007)

Galajinsky, Anton, Lechtenfeld, Olaf, Polovnikov, Kirill

We continue the research initiated in hep-th/0607215 and apply our method of conformal automorphisms to generate various N=4 superconformal quantum many-body systems on the real line from a set of...

Supersymmetric noncommutative solitons (2007)

Quiver Gauge Theory and Noncommutative Vortices (2007)

I consider a supersymmetric Bogomolny-type model in 2+1 dimensions originating from topological string theory. By a gauge fixing this model is reduced to a supersymmetric U(n) chiral model with a...

Lechtenfeld, Olaf, Popov, Alexander D., Szabo, Richard J.

We construct explicit BPS and non-BPS solutions of the Yang-Mills equations on noncommutative spaces R^{2n}_theta x G/H which are manifestly G-symmetric. Given a G-representation, by twisting with a...

Hierarchy of N=8 Mechanics Models (2007)

Ivanov, Evgeny, Lechtenfeld, Olaf, Sutulin, Anton

Using the N=4 superspace approach in one dimension (time), we construct general N=8 supersymmetric mechanics actions for the multiplets (b,8,8-b) classified in hep-th/0406015, with the main focus on...

Noncommutative Solitons in a Supersymmetric Chiral Model in 2+1 Dimensions (2007)

Construction of Noncommutative Instantons in 4k Dimensions (2007)

We consider a supersymmetric Bogomolny-type model in 2+1 dimensions originating from twistor string theory. By a gauge fixing this model is reduced to a modified U(n) chiral model with N

Broedel, Johannes, Ivanova, Tatiana A., Lechtenfeld, Olaf

We consider generalized self-duality equations for U(2r) Yang-Mills theory on R^{4k} with quaternionic structure and self-dual Moyal deformation. We employ the extended ADHM method in 4k dimensions...

Calogero models and nonlocal conformal transformations (2006)

Galajinsky, Anton, Lechtenfeld, Olaf, Polovnikov, Kirill

We propose a universal method of relating the Calogero model to a set of decoupled particles on the real line, which can be uniformly applied to both the conformal and nonconformal versions as well...

Noncommutative Solitons (2006)

Moduli-Space Dynamics of Noncommutative Abelian Sigma-Model Solitons (2006)

These lectures deal mainly with solitons in three-dimensional Moyal-deformed sigma models. The topics are: static and moving (multi-)solitons of the (integrable) Ward sigma model, with space-space...

Klawunn, Michael, Lechtenfeld, Olaf, Petersen, Stefan

In the noncommutative (Moyal) plane, we relate exact U(1) sigma-model solitons to generic scalar-field solitons for an infinitely stiff potential. The static k-lump moduli space C^k/S_k features a...

Rank Two Quiver Gauge Theory, Graded Connections and Noncommutative Vortices (2006)

Lechtenfeld, Olaf, Popov, Alexander D., Szabo, Richard J.

We consider equivariant dimensional reduction of Yang-Mills theory on K"ahler manifolds of the form M times CP^1 times CP^1. This induces a rank two quiver gauge theory on M which can be formulated...

Noncommutative Instantons on CP^n (2006)

Matrix Models and D-branes in Twistor String Theory (2005)

We construct explicit solutions of the Hermitian Yang-Mills equations on the noncommutative space C^n_\theta. In the commutative limit they coincide with the standard instantons on CP^n written in...

Lechtenfeld, Olaf, Saemann, Christian

We construct two matrix models from twistor string theory: one by dimensional reduction onto a rational curve and another one by introducing noncommutative coordinates on the fibres of the...

Emergence of Time from Dimensional Reduction in Noncommutative Geometry (2005)

Chu, Chong-Sun, Lechtenfeld, Olaf

By considering a new form of dimensional reduction for noncommutative field theory, we show that the signature of spacetime may be changed. In particular, it is demonstrated that a temporal dimension...

Time-Space Noncommutative Abelian Solitons (2005)

Chu, Chong-Sun, Lechtenfeld, Olaf

We demonstrate the construction of solitons for a time-space Moyal-deformed integrable U(n) sigma model (the Ward model) in 2+1 dimensions. These solitons cannot travel parallel to the noncommutative...

Noncommutative Instantons in 4k Dimensions (2005)

Sigma-Model Solitons in the Noncommutative Plane: Construction and Stability Analysis (2004)

We consider Ward's generalized self-duality equations for U(2r) Yang-Mills theory on R^{4k} and their Moyal deformation under self-dual noncommutativity. Employing an extended ADHM construction we...

Domrin, Andrei V., Lechtenfeld, Olaf, Petersen, Stefan

Noncommutative multi-solitons are investigated in Euclidean two-dimensional U(n) and Grassmannian sigma models, using the auxiliary Fock-space formalism. Their construction and moduli spaces are...

Noncommutative Sine-Gordon Model (2004)

Non-anticommutative deformation of N=(1,1) hypermultiplets (2004)

As I briefly review, the sine-Gordon model may be obtained by dimensional and algebraic reduction from 2+2 dimensional self-dual U(2) Yang-Mills through a 2+1 dimensional integrable U(2) sigma model....

Ivanov, Evgeny, Lechtenfeld, Olaf, Zupnik, Boris

We study the SO(4)xSU(2) invariant and N=(1,0) supersymmetry-preserving nilpotent (non-anticommutative) Moyal deformation of hypermultiplets interacting with an abelian gauge multiplet, starting from...

Supertwistors and Cubic String Field Theory for Open N=2 Strings (2004)

Integrable Noncommutative Sine-Gordon Model (2004)

The known Lorentz invariant string field theory for open N=2 strings is combined with a generalization of the twistor description of anti-self-dual (super) Yang-Mills theories. We introduce a...

Lechtenfeld, Olaf, Mazzanti, Liuba, Penati, Silvia, Popov, Alexander D., Tamassia, Laura

Requiring an infinite number of conserved local charges or the existence of an underlying linear system does not uniquely determine the Moyal deformation of 1+1 dimensional integrable field theories....

Noncommutative Moduli for Multi-Instantons (2004)

Ivanova, Tatiana A., Lechtenfeld, Olaf, Mueller-Ebhardt, Helge

There exists a recursive algorithm for constructing BPST-type multi-instantons on commutative R^4. When deformed noncommutatively, however, it becomes difficult to write down non-singular instanton...

Noncommutative Instantons and Solitons (2004)

A note on fermionic flows of the N=(1|1) supersymmetric Toda lattice hierarchy (2004)

I explain how to construct noncommutative BPS configurations in four and lower dimensions by solving linear matrix equations. Examples are instantons in D=4 Yang-Mills, monopoles in D=3...

Lechtenfeld, Olaf, Sorin, Alexander S.

We extend the Sato equations of the N=(1|1) supersymmetric Toda lattice hierarchy by two new infinite series of fermionic flows and demonstrate that the algebra of the flows of the extended hierarchy...

N=4, d=1 supermultiplets from nonlinear realizations of D(2,1;\alpha) (2003)

Ivanov, Evgeny, Krivonos, Sergey, Lechtenfeld, Olaf

Proceeding from nonlinear realizations of the most general N=4, d=1 superconformal symmetry associated with the supergroup D(2,1;\alpha), we construct all known and two new off-shell N=4, d=1...

Noncommutative Instantons in Higher Dimensions, Vortices and Topological K-Cycles (2003)

Lechtenfeld, Olaf, Popov, Alexander D., Szabo, Richard J.

We construct explicit BPS and non-BPS solutions of the U(2k) Yang-Mills equations on the noncommutative space R^{2n}_\theta x S^2 with finite energy and topological charge. By twisting with a Dirac...

Nilpotent deformations of N=2 superspace (2003)

Ivanov, Evgeny, Lechtenfeld, Olaf, Zupnik, Boris

We investigate deformations of four-dimensional N=(1,1) euclidean superspace induced by nonanticommuting fermionic coordinates. We essentially use the harmonic superspace approach and consider...

Noncommutative Monopoles and Riemann-Hilbert Problems (2003)

Noncommutative Multi-Instantons on R^{2n} x S^2 (2003)

The Bogomolny equations for Yang-Mills-Higgs monopoles follow from a system of linear equations which may be solved through a parametric Riemann-Hilbert problem. We extend this approach to...

Solving String Field Equations: New Uses for Old Tools (2002)

Generalizing self-duality on R^2 x S^2 to higher dimensions, we consider the Donaldson-Uhlenbeck-Yau equations on R^{2n} x S^2 and their noncommutative deformation for the gauge group U(2). Imposing...

Kling, Alexander, Lechtenfeld, Olaf, Popov, Alexander D., Uhlmann, Sebastian

It is argued that the (NS-sector) superstring field equations are integrable, i.e. their solutions are obtainable from linear equations. We adapt the 25-year-old solution-generating "dressing" method...

Noncommutative Instantons via Dressing and Splitting Approaches (2002)

Horvath, Zalan, Lechtenfeld, Olaf, Wolf, Martin

Almost all known instanton solutions in noncommutative Yang-Mills theory have been obtained in the modified ADHM scheme. In this paper we employ two alternative methods for the construction of the...

On Nonperturbative Solutions of Superstring Field Theory (2002)

Kling, Alexander, Lechtenfeld, Olaf, Popov, Alexander D., Uhlmann, Sebastian

Nonperturbative solutions to the nonlinear field equations in the NS sector of cubic as well as nonpolynomial superstring field theory can be obtained from a linear equation which includes a...

Exact Solutions of Berkovits' String Field Theory (2002)

Lechtenfeld, Olaf, Popov, Alexander D., Uhlmann, Sebastian

The equation of motion for Berkovits' WZW-like open (super)string field theory is shown to be integrable in the sense that it can be written as the compatibility condition ("zero-curvature...

Light-Cone Gauge for N=2 Strings (2002)

Lechtenfeld, Olaf, Siegel, Warren

Covariant quantization of self-dual strings in 2+2 flat dimensions reduces them to their zero modes, a consequence of extended world-sheet supersymmetry. We demonstrate how to arrive at the same...

Noncommutative 't Hooft Instantons (2001)

Scattering of Noncommutative Solitons in 2+1 Dimensions (2001)

We employ the twistor approach to the construction of U(2) multi-instantons `a la 't Hooft on noncommutative R^4. The noncommutative deformation of the Corrigan-Fairlie-'t Hooft-Wilczek ansatz is...

Noncommutative Multi-Solitons in 2+1 Dimensions (2001)

Interactions of noncommutative solitons in a modified U(n) sigma model in 2+1 dimensions can be analyzed exactly. Using an extension of the dressing method, we construct explicit time-dependent...

Noncommutative Solitons in Open N=2 String Theory (2001)

The study of noncommutative solitons is greatly facilitated if the field equations are integrable, i.e. result from a linear system. For the example of a modified but integrable U(n) sigma model in...

Lechtenfeld, Olaf, Popov, Alexander D., Spendig, Bernd

Coincident D2-branes in open N=2 fermionic string theory with a B-field background yield an integrable modified U(n) sigma model on noncommutative R^{2,1}. This model provides a showcase for an...

A Heterotic N=2 String with Space-Time Supersymmetry (2001)

Bellucci, Stefano, Galajinsky, Anton, Lechtenfeld, Olaf

We reconsider the issue of embedding space-time fermions into the four-dimensional N=2 world-sheet supersymmetric string. A new heterotic theory is constructed, taking the right-movers from the N=4...

Open N=2 strings in a B-field background and noncommutative self-dual Yang-Mills (2000)

Lechtenfeld, Olaf, Popov, Alexander D., Spendig, Bernd

In the presence of D-branes, fermionic N=2 strings in 2+2 dimensions can be coupled to a K"ahler NS-NS two-form B. We present the corresponding action which produces N=2 supersymmetric boundary...

On the Integrability of Covariant Field Theory for Open N=2 Strings (2000)

Hidden N=(2|2) supersymmetry of the N=(1|1) supersymmetric Toda lattice hierarchy (2000)

We discuss the integrability of the Berkovits-Siegel open string field equations and derive an infinite set of their non-local (solution-generating) symmetries. The string field equations are...

Hidden Symmetries of the Open N=2 String (2000)

An N=(2|2) superfield formulation of the N=(1|1) supersymmetric Toda lattice hierarchy is proposed, and its five real forms are presented.

N=2 Quantum String Scattering (2000)

It is known for ten years that self-dual Yang-Mills theory is the effective field theory of the open N=2 string in 2+2 dimensional spacetime. We uncover an infinite set of abelian rigid string...

Chalmers, Gordon, Lechtenfeld, Olaf, Niemeyer, Bernd

We calculate the genus-one three- and four-point amplitudes in the 2+2 dimensional closed N=(2,2) worldsheet supersymmetric string within the RNS formulation. Vertex operators are redefined with the...

Hidden Symmetries of the Open N=2 String (2000)

The Erwin, Schrodinger International Boltzmanngasse, Olaf Lechtenfeld, Tatiana A. Ivanova, Tatiana A. Ivanova

It is known for ten years that self-dual Yang-Mills theory is the eective eld theory of the open N=2 string in 2+2 dimensional spacetime. We uncover an innite set of abelian rigid string symmetries,...

Mathematics and Physics of N=2 Strings (1999)

Closed N=2 Strings: Picture-Changing, Hidden Symmetries and SDG Hierarchy (1999)

Open and closed strings with two worldsheet supersymmetries in 2+2 dimensional spacetime are reviewed in the NSR formulation. I briefly discuss their quantization, mutual and self-interactions,...

Real forms of the complex twisted N=2 supersymmetric Toda chain hierarchy in real N=1 and twisted N=2 superspaces (1999)

We study the action of picture-changing and spectral flow operators on a ground ring of ghost number zero operators in the chiral BRST cohomology of the closed N=2 string and describe an infinite set...

Ward identities and the vanishing theorem for loop amplitudes of the closed N=2 string (1999)

Three nonequivalent real forms of the complex twisted N=2 supersymmetric Toda chain hierarchy (solv-int/9907021) in real N=1 superspace are presented. It is demonstrated that they possess a global...

Junemann, Klaus, Lechtenfeld, Olaf

The existence of a ground ring of ghost number zero operators in the chiral BRST cohomology of the N=2 string is used to derive an infinite set of Ward identities for the closed-string scattering...

Supersymmetric KP hierarchy in N=1 superspace and its N=2 reductions (1999)

Lechtenfeld, Olaf, Louis, Jan, Lüst, Dieter, Nicolai, Hermann C

A wide class of N=2 reductions of the supersymmetric KP hierarchy in N=1 superspace is described. This class includes a new N=2 supersymmetric generalization of the Toda chain hierarchy. The Lax pair...

Strings '99 (1999)

Towards a stringy extension of self-dual super Yang-Mills (1999)

Galajinsky, Anton, Lechtenfeld, Olaf

Motivated by the search for a space-time supersymmetric extension of the N=2 string, we construct a particle model which, upon quantization, describes (abelian) self-dual super Yang-Mills in 2+2...

Non-local symmetries of the closed N=2 string (1999)

Junemann, Klaus, Lechtenfeld, Olaf, Popov, Alexander D.

By carefully analysing the picture-dependence of the BRST cohomology an infinite set of symmetry charges of the closed N=2 string is identified. The transformation laws of the physical vertex...

Manifestly invariant actions for harmonic self-dual gauge theory (1998)

Lechtenfeld, Olaf, Zupnik, Boris

We discuss alternative descriptions of four-dimensional self-dual Yang-Mills fields in harmonic space with additional commuting spinor coordinates. In particular, the linear analyticity equation and...

Fermionic flows and tau function of the N=(1|1) superconformal Toda lattice hierarchy (1998)

String-induced Yang-Mills coupling to self-dual gravity (1998)

An infinite class of fermionic flows of the N=(1|1) superconformal Toda lattice hierarchy is constructed and their algebraic structure is studied. We completely solve the semi-infinite N=(1|1) Toda...

Devchand, Chandrashekar, Lechtenfeld, Olaf

By considering N=2 string amplitudes we determine the (2+2)-dimensional target space action for the physical degrees of freedom: self-dual gravity and self-dual Yang-Mills, together with their...

On the Self-Dual Geometry of N=2 Strings (1998)

Devchand, Chandrashekar, Lechtenfeld, Olaf

We discuss the precise relation of the open N=2 string to a self-dual Yang-Mills (SDYM) system in 2+2 dimensions. In particular, we review the description of the string target space action in terms...

String-induced Yang-Mills coupling to self-dual gravity (1998)

Rashekar Devch, Chandrashekar Devchand, Olaf Lechtenfeld, Olaf Lechtenfeld

By considering N=2 string amplitudes we determine the (2+2)-dimensional target space action for the physical degrees of freedom: self-dual gravity and self-dual YangMills, together with their...

On the self-dual geometry of N=2 strings (1998)

Rashekar Devch, Olaf Lechtenfeld, Chandrashekar Devchand

: We discuss the precise relation of the open N=2 string to a self-dual Yang-Mills (SDYM) system in 2+2 dimensions. In particular, we review the description of the string target space action in terms...

Chiral BRST Cohomology of N=2 Strings at Arbitrary Ghost and Picture Number (1997)

Junemann, Klaus, Lechtenfeld, Olaf

We compute the BRST cohomology of the holomorphic part of the N=2 string at arbitrary ghost and picture number. We confirm the expectation that the relative cohomology at non-zero momentum consists...

Extended Self-Dual Yang-Mills from the N=2 String (1997)

Devchand, Chandrashekar, Lechtenfeld, Olaf

We show that the physical degrees of freedom of the critical open string with N=2 superconformal symmetry on the worldsheet are described by a self-dual Yang-Mills field on a hyperspace parametrised...

N=2 Worldsheet Instantons Yield Cubic Self-Dual Yang-Mills (1997)

Lechtenfeld, Olaf, Siegel, Warren

When the gauge instantons on the N=2 string worldsheet are properly included in the sum over topologies, the breaking of SO(2,2) Lorentz symmetry in R^{2,2} is parametrized by a spacetime twistor...

Extended self-dual Yang-Mills from the N=2 String (1997)

Rashekar Devch, Chandrashekar Devchand, Olaf Lechtenfeld, Olaf Lechtenfeld

We show that the physical degrees of freedom of the critical open string with N=2 superconformal symmetry on the worldsheet are described by a self-dual Yang-Mills field on a hyperspace parametrised...

Path-Integral Quantization of the (2,2) String (1996)

Bischoff, Jan, Lechtenfeld, Olaf

A complete treatment of the (2,2) NSR string in flat (2+2) dimensional space-time is given, from the formal path integral over N=2 super Riemann surfaces to the computational recipe for amplitudes at...

Scalar Deformations of Schwarzschild Holes and Their Stability (1996)

Dennhardt, Helge, Lechtenfeld, Olaf

We construct two solutions of the minimally coupled Einstein-scalar field equations, representing regular deformations of Schwarzschild black holes by a self-interacting, static, scalar field. One...

Restoring Reality for the Self-Dual N=2 String (1996)

Bischoff, Jan, Lechtenfeld, Olaf

It is known that the critical N=(2,2) string describes 2+2 dimensional self-dual gravity in a non-covariant form, since it requires the choice of a complex structure in the target, which leaves only...

The Self-Dual Critical N=2 String (1996)

Integration Measure and Spectral Flow in the Critical N=2 String (1995)

I review the covariant quantization of the closed fermionic string with (2,2) extended world-sheet supersymmetry on R^{2,2}. Results on n-point scattering amplitudes are presented, for tree- and...

On the BRST Cohomology of N=2 Strings (1995)

I present the moduli space of the (2+2)-dimensional critical closed fermionic string with two world-sheet supersymmetries. The integration of fermionic and Maxwell moduli in the presence of punctures...

The String Measure and Spectral Flow of Critical N=2 Strings (1995)

We analyze the BRST cohomology of the critical N=2 NSR string using chiral bosonization. Picture-changing and spectral flow is made explicit in a holomorphic field basis. The integration of fermionic...

Ketov, Sergei, Lechtenfeld, Olaf

The general structure of N=2 moduli space at arbitrary genus and instanton number is investigated. The N=2 NSR string measure is calculated, yielding picture- and U(1) ghost number-changing operator...

Exact Black-Hole Solution With Self-Interacting Scalar Field (1995)

Bechmann, Olaf, Lechtenfeld, Olaf

Einstein gravity minimally coupled to a self-interacting scalar field is investigated in the static and isotropic situation. We explicitly construct in partially closed form a new black-hole solution...

From N=2 Fermionic Strings to Superstrings? (1994)

Collective Field Theory for D=0 Matrix Models (1993)

I review the covariant quantization of the critical $N{=}2$ fermionic string with and without a global ${\bf Z}_2$ twist. The BRST analysis yields massless bosonic and fermionic vertex operators in...

Dilaton Gravity and No-Hair Theorem in Two Dimensions (1992)

I investigate non-perturbative aspects of zero-dimensional matrix models. Subtleties in the large-$N$ limit of the semiclassical picture are pointed out. The tunneling of eigenvalues is seen to...

Lechtenfeld, Olaf, Nappi, Chiara

We study a general class of two-dimensional theories of the dilaton-gravity type inspired by string theory and show that they admit charged multiple-horizon black holes. These solutions are proved to...

Semiclassical Approach to Finite-N Matrix Models (1991)