arXiv subjects

Clifford V. Johnson

Publications and source records attributed to Clifford V. Johnson.

At least 127 records · Page 7Linked to original sources

arXiv1998

On Second-Quantized Open Superstring Theory

The SO(32) theory, in the limit where it is an open superstring theory, is completely specified in the light-cone gauge as a second-quantized string theory in terms of a ``matrix string'' model. The theory is defined by the neighbourhood of a 1+1 dimensional fixed point theory, characterized by an Abelian gauge theory with type IB Green-Schwarz form. Non-orientability and SO(32) gauge symmetry arise naturally, and the theory effectively constructs an orientifold projection of the (weakly coupled) matrix type IIB theory (also discussed herein). The fixed point theory is a conformal field theory with boundary, defining the free string theory. Interactions involving the interior of open and closed strings are governed by a twist operator in the bulk, while string end-points are created and destroyed by a boundary twist operator.

hep-th↗

arXiv1998

Putting String Duality to Work

This presentation is intended to give a flavour of the physics to be studied and discovered by exploiting the interface between string theory, M-theory and field theory provided by the dynamics of extended objects called `branes', and their relationships under string duality. It is quite non-technical, with very few equations but many pictorial illustrations to aid the reader. There is only a moderate amount of text, as the content is based upon transparencies which were intended to be accompanied by extra words. (Hyperlinked transparencies of a talk given at the annual UK Particle Theory Meeting,Rutherford Appleton Laboratories, Didcot, Oxfordshire, England, 15th December 1997.)

hep-th↗

arXiv1997

Anatomy of a Duality

The nature of M-theory on K3 X I, where I is a line interval, is considered, with a view towards formulating a `matrix theory' representation of that situation. Various limits of this compactification of M-theory yield a number of well known N=1 six dimensional compactifications of the heterotic and type I string theories. Geometrical relations between these limits give rise to string/string dualities between some of these compactifications. At a special point in the moduli space of compactifications, this motivates a partial definition of the matrix theory representation of the M-theory on K3 X I as the large N limit of a certain type IA orientifold model probed by a conglomerate of N D-branes. Such a definition in terms of D-branes and orientifold planes is suggestive, but necessarily incomplete, due to the low amount of superymmetry. It is proposed - following hints from the orientifold model - that the complete matrix theory representation of the K3 X I compactified M-theory is given by the large N limit of compactification - on a suitable `dual' surface - of the `little heterotic string' N = 1 six dimensional quantum theories.

hep-th↗

arXiv1997

From M-theory to F-theory, with Branes

A duality relationship between certain brane configurations in type IIA and type IIB string theory is explored by exploiting the geometrical origins of each theory in M-theory. The configurations are dual ways of realising the non-perturbative dynamics of a four dimensional N=2 supersymmetric SU(2) gauge theory with four or fewer favours of fermions in the fundamental, and the spectral curve which organizes these dynamics plays a prominent role in each case. This is an illustration of how non-trivial F-theory backgrounds follow from M-theory ones, hopefully demystifying somewhat the origins of the former.

hep-th↗

arXiv1997

On the Orientifolding of Type II NS-Fivebranes

Dualities between certain supersymmetric gauge field theories in three and four dimensions have been studied in considerable detail recently, by realizing them as geometric manipulations of configurations of extended objects in type II string theory. These extended objects include `D-branes' and `NS-(five)branes'. In constructing the brane configurations which realize dualities for orthogonal and symplectic gauge groups, an `orientifold' was introduced, which results in non-orientable string sectors. Certain features of orientifolded NS-branes -such as their existence- were assumed in the original construction, which have not been verified directly. However, those features fit very well together with the properties of the relevant field theories, and subsequently yielded the known dualities. This letter describes how orientifolded NS-branes can exist in type II string theory by displaying explicitly that the assumed combinations of world-sheet and space-time symmetries do indeed leave the NS-brane invariant and therefore can be gauged. The resulting orientifolded NS-brane can be described in terms of background fields, and furthermore as an exact conformal field theory, to exactly the same extent as the standard NS-brane.

hep-th↗

arXiv1997

Orientifolds, Branes, and Duality of 4D Gauge Theories

Recently, a D-brane construction in type IIA string theory was shown to yield the electric/magnetic duality of four dimensional N=1 supersymmetric U(N_c) gauge theories with N_f flavours of quark. We present here an extension of that construction which yields the electric/magnetic duality for the SO(N_c) and USp(N_c) gauge theories with N_f quarks, by adding an orientifold plane which is consistent with the supersymmetry. Due to the intersection of the orientifold plane with the NS-NS fivebranes already present, new features arise which are crucial in determining the correct final structure of the dualities.

hep-th↗

arXiv1996

Notes on D-Branes

This is a series of remedial lectures on open and unoriented strings for the heterotic string generation. The particular focus is on the interesting features that arise under T-duality---D-branes and orientifolds. The final lecture discusses the application to string duality. There will be no puns. Lectures presented by J. P. at the ITP from Nov. 16 to Dec. 5, 1995. References updated through Jan. 25, 1996.

hep-th↗

arXiv1996

Aspects of Type IIB Theory on ALE Spaces

D-brane technology and strong/weak coupling duality supplement traditional orbifold techniques by making certain background geometries more accessible. In this spirit, we consider some of the geometric properties of the type IIB theory on R^6 \times M where M is an `Asymptotically Locally Euclidean (ALE)' gravitational instanton. Given the self-duality of the theory, we can extract the geometry (both singular and resolved) seen by the weakly coupled IIB string by studying the physics of a D1-brane probe. The construction is both amusing and instructive, as the physics of the probe completely captures the mathematics of the construction of ALE instantons via `HyperKahler Quotients', as presented by Kronheimer. This relation has been noted by Douglas and Moore for the A-series. We extend the explicit construction to the case of the D- and E-series -- uncovering a quite beautiful structure -- and highlight how all of the elements of the mathematical construction find their counterparts in the physics of the type IIB D-string. We discuss the explicit ALE metrics which may be obtained using these techniques, and comment on the role duality plays in relating gauged linear sigma models to conformal field theories.

hep-th↗

arXiv1996

Introduction to D-Branes, with Applications

A brief review of some of the central ideas, terminology and techniques of the technology of orientifolds and D-branes is presented. Some applications are reviewed, including the construction of dual solitonic strings in the context of string/string duality, the computation of the Bekenstein-Hawking entropy/area law for extremal black holes, and the construction of N=1 string vacua in dimensions lower than ten. (Contribution to the proceedings of the fourth International Workshop on Supersymmetry and Unification of Fundamental Interactions (SUSY '96), held at the University of Maryland at College Park, May 29 - June 1, 1996.)

hep-th↗

arXiv1996

K3 Orientifolds

We study string theory propagating on R^6 times K3 by constructing orientifolds of Type IIB string theory compactified on the T^4/Z_N orbifold limits of the K3 surface. This generalises the Z_2 case studied previously. The orientifold models studied may be divided into two broad categories, sometimes related by T-duality. Models in category A require either both D5- and D9-branes, or only D9-branes, for consistency. Models in category B require either only D5-branes, or no D-branes at all. This latter case is an example of a consistent purely closed unoriented string theory. The spectra of the resulting six dimensional N=1 supergravity theories are presented. Precise statements are made about the relation of the Z_N ALE spaces and D5-branes to instantons in the dual heterotic string theory.

hep-th↗

arXiv1996

Multiple Realisations of N=1 Vacua in Six Dimensions

A while ago, examples of N=1 vacua in D=6 were constructed as orientifolds of Type IIB string theory compactified on the K3 surface. Among the interesting features of those models was the presence of D5-branes behaving like small instantons, and the appearance of extra tensor multiplets. These are both non-perturbative phenomena from the point of view of heterotic string theory. Although the orientifold models are a natural setting in which to study these non-perturbative Heterotic string phenomena, it is interesting and instructive to explore how such vacua are realised in Heterotic string theory, M-theory and F-theory, and consider the relations between them. In particular, we consider models of M-theory compactified on K3 x S^1/Z_2 with fivebranes present on the interval. There is a family of such models which yields the same spectra as a subfamily of the orientifold models. By further compactifying on T^2 to four dimensions we relate them to Heterotic string spectra. We then use Heterotic/Type IIA duality to deduce the existence of Calabi-Yau 3-folds which should yield the original six dimensional orientifold spectra if we use them to compactify F-theory. Finally, we show in detail how to take a limit of such an F-theory compactification which returns us to the Type IIB orientifold models.

hep-th↗

arXiv1996

Entropy of 4D Extremal Black Holes

We derive the Bekenstein-Hawking entropy formula for four-dimensional Reissner-Nordstrom extremal black holes in type II string theory. The derivation is performed in two separate (T-dual) weak coupling pictures. One uses a type IIB bound state problem of D5- and D1-branes, while the other uses a bound state problem of D0- and D4-branes with macroscopic fundamental type IIA strings. In both cases, the D-brane systems are also bound to a Kaluza-Klein monopole, which then yields the four-dimensional black hole at strong coupling.

hep-th↗

arXiv1995

Is string theory a theory of strings?

Recently a great deal of evidence has been found indicating that type IIA string theory compactified on K3 is equivalent to heterotic string theory compactified on T^4. Under the transformation which relates the two theories, the roles of fundamental and solitonic string solutions are interchanged. In this letter we show that there exists a solitonic membrane solution of the heterotic string theory which becomes a singular solution of the type IIA theory, and should therefore be interpreted as a fundamental membrane in the latter theory. We speculate upon the implications that the complete type IIA theory is a theory of membranes, as well as strings.

hep-th↗

arXiv1995

Heterotic Coset Models and (0,2) String Vacua

A Lagrangian definition of a large family of (0,2) supersymmetric conformal field theories may be made by an appropriate gauge invariant combination of a gauged Wess-Zumino-Witten model, right-moving supersymmetry fermions, and left-moving current algebra fermions. Throughout this paper, use is made of the interplay between field theoretic and algebraic techniques (together with supersymmetry) which is facilitated by such a definition. These heterotic coset models are thus studied in some detail, with particular attention paid to the (0,2) analogue of the N=2 minimal models, which coincide with the `monopole' theory of Giddings, Polchinski and Strominger. A family of modular invariant partition functions for these (0,2) minimal models is presented. Some examples of N=1 supersymmetric four dimensional string theories with gauge groups E_6 X G and SO(10) X G are presented, using these minimal models as building blocks. The factor G represents various enhanced symmetry groups made up of products of SU(2) and U(1).

hep-th↗

arXiv1995

Heterotic Coset Models

A description is given of how to construct (0,2) supersymmetric conformal field theories as coset models. These models may be used as non-trivial backgrounds for Heterotic String Theory. They are realised as a combination of an anomalously gauged Wess-Zumino-Witten model, right-moving supersymmetric fermions, and left-moving current algebra fermions. Requiring the sum of the gauge anomalies from the bosonic and fermionic sectors to cancel yields the final model. Applications discussed include exact models of extremal four-dimensional charged black holes and Taub-NUT solutions of string theory. These coset models may also be used to construct important families of (0,2) supersymmetric Heterotic String compactifications. The Kazama-Suzuki models are the left-right symmetric special case of these models.

hep-th↗

arXiv1995

A Conformal Field Theory of a Rotating Dyon

A conformal field theory representing a four-dimensional classical solution of heterotic string theory is presented. The low-energy limit of this solution has U(1) electric and magnetic charges, and also nontrivial axion and dilaton fields. The low-energy metric contains mass, NUT and rotation parameters. We demonstrate that this solution corresponds to part of an extremal limit of the Kerr-Taub-NUT dyon solution. This limit displays interesting `remnant' behaviour, in that asymptotically far away from the dyon the angular momentum vanishes, but far down the infinite throat in the neighbourhood of the horizon (described by our CFT) there is a non-zero angular velocity. A further natural generalization of the CFT to include an additional parameter is presented, but the full physical interpretation of its role in the resulting low energy solution is unclear.

hep-th↗

arXiv1994

Stringy Twists of the Taub--Nut Metric

In the low-energy limit, string theory has two remarkable symmetries, O(d,d+p) and SL(2,R). We illustrate the use of these transformations as techniques to generate new solutions by applying them to the Taub--NUT metric.

hep-th↗

arXiv1994

Heterotic Cosets

A description is given of how to construct $(0,2)$ supersymmetric conformal field theories as coset models. These models may be used as non--trivial backgrounds for Heterotic String Theory. They are realised as a combination of an anomalously gauged Wess--Zumino--Witten model, right--moving supersymmetric fermions, and left--moving current algebra fermions. Requiring the sum of the gauge anomalies from the bosonic and fermionic sectors to cancel yields the final model. Applications discussed include exact models of extremal four--dimensional charged black holes and Taub--NUT solutions of string theory. These coset models may also be used to construct important families of $(0,2)$ supersymmetric Heterotic String compactifications. The Kazama--Suzuki models are the left--right symmetric special case of these models.

hep-th↗