Twistor Superstring in 2T-Physics

By utilizing the gauge symmetries of Two-Time Physics (2T-physics), a superstring with linearly realized global SU(2,2|4) supersymmetry in 4+2 dimensions (plus internal degrees of freedom) is constructed. It is shown that the dynamics of the Witten-Berkovits twistor superstring in 3+1 dimensions emerges as one of the many one time (1T) holographic pictures of the 4+2 dimensional string obtained via gauge fixing of the 2T gauge symmetries. In 2T-physics the twistor language can be transformed to usual spacetime language and vice-versa, off shell, as different gauge fixings of the same 2T string theory. Further holographic string pictures in 3+1 dimensions that are dual theories can also be derived. The 2T superstring is further generalized in the SU(4)=SO(6) sector of SU(2,2|4) by the addition of six bosonic dimensions, for a total of 10+2 dimensions. Excitations of the extra bosons produce a SU(2,2|4) current algebra spectrum that matches the classification of the high spin currents of N=4, d=4 super Yang Mills theory which are conserved in the weak coupling limit. This spectrum is interpreted as the extension of the SU(2,2|4 classification of the Kaluza-Klein towers of typeII-B supergravity compactified on AdS{5}xS(5), into the full string theory, and is speculated to have a covariant 10+2 origin in F-theory or S-theory. Further generalizations of the superstring theory to 3+2, 5+2 and 6+2 dimensions, based on the supergroups OSp(8|4), F(4), OSp(8*|4) respectively, and other cases, are also discussed. The OSp(8|4) case in 6+2 dimensions can be gauge fixed to 5+1 dimensions to provide a formulation of the special superconformal theory in six dimensions either in terms of ordinary spacetime or in terms of twistors.Comment: 26 pages, LaTeX. In version 3, section 5, it is argued that the 6+2 2T-superstring with OSp(8*|4) supersymmetry provides a description of the special d=6 superconformal theory based on the tensor supermultiplet (not d=6 SYM as mentioned in version 2

STRINGY EVIDENCE FOR D=11 STRUCTURE IN STRONGLY COUPLED TYPE II-A SUPERSTRING

Witten proposed that the low energy physics of strongly coupled D=10 type-IIA superstring may be described by D=11 supergravity. To explore the stringy aspects of the underlying theory we examine the stringy massive states. We propose a systematic formula for identifying non-perturbative states in D=10 type-IIA superstring theory, such that, together with the elementary excited string states, they form D=11 supersymmetric multiplets multiplets in SO(10) representations. This provides hints for the construction of a weakly coupled D=11 theory that is dual to the strongly coupled D=10 type IIA superstring.Comment: LaTeX, revtex, 2-column, 10 pages

Non-Singular String-Cosmologies From Exact Conformal Field Theories

Non-singular two and three dimensional string cosmologies are constructed using the exact conformal field theories corresponding to SO(2,1)/SO(1,1) and SO(2,2)/SO(2,1). {\it All} semi-classical curvature singularities are canceled in the exact theories for both of these cosets, but some new quantum curvature singularities emerge. However, considering different patches of the global manifolds, allows the construction of non-singular spacetimes with cosmological interpretation. In both two and three dimensions, we construct non-singular oscillating cosmologies, non-singular expanding and inflationary cosmologies including a de Sitter (exponential) stage with positive scalar curvature as well as non-singular contracting and deflationary cosmologies. Similarities between the two and three dimensional cases suggest a general picture for higher dimensional coset cosmologies: Anisotropy seems to be a generic unavoidable feature, cosmological singularities are generically avoided and it is possible to construct non-singular cosmologies where some spatial dimensions are experiencing inflation while the others experience deflation.Comment: Talk presented at the D.V. Volkov Memorial Conference "Supersymmetry and Quantum Field Theory" (25-29 July, 2000, Kharkov, Ukraine). Published in Nucl.Phys.B. (Proc. Suppl.) 102&103 (2001), p. 20

Superstar in Noncommutative Superspace via Covariant Quantization of the Superparticle

A covariant quantization method is developed for the off-shell superparticle in 10 dimensions. On-shell it is consistent with lightcone quantization, while off-shell it gives a noncommutative superspace that realizes non-linearly a hidden 11-dimensional super Poincare symmetry. The non-linear commutation rules are then used to construct the supersymmetric generalization of the covariant Moyal star product in noncommutative superspace. As one of the possible applications, we propose this new product as the star product in supersymmetric string field theory. Furthermore, the formalism introduces new techniques and concepts in noncommutative (super)geometry.Comment: 17 pages, LaTe

The bosonic string and superstring models in 26+2 and 10+2 dimensional space--time, and the generalized Chern-Simons action

We have covariantized the Lagrangians of the U(1)_V * U(1)_A models, which have U(1)_V * U(1)_A gauge symmetry in two dimensions, and studied their symmetric structures. The special property of the U(1)_V * U(1)_A models is the fact that all these models have an extra time coordinate in the target space-time. The U(1)_V * U(1)_A models coupled to two-dimensional gravity are string models in 26+2 dimensional target space-time for bosonic string and in 10+2 dimensional target space-time for superstring. Both string models have two time coordinates. In order to construct the covariant Lagrangians of the U(1)_V * U(1)_A models the generalized Chern-Simons term plays an important role. The supersymmetric generalized Chern-Simons action is also proposed. The Green-Schwarz type of U(1)_V * U(1)_A superstring model has another fermionic local symmetry as well as \kappa-symmetry. The supersymmetry of target space-time is different from the standard one.Comment: 27 pages, no figure

Noncommutative Sp(2,R) Gauge Theories - A Field Theory Approach to Two-Time Physics

Phase-space and its relativistic extension is a natural space for realizing Sp(2,R) symmetry through canonical transformations. On a Dx2 dimensional covariant phase-space, we formulate noncommutative field theories, where Sp(2,R) plays a role as either a global or a gauge symmetry group. In both cases these field theories have potential applications, including certain aspects of string theories, M-theory, as well as quantum field theories. If interpreted as living in lower dimensions, these theories realize Poincare' symmetry linearly in a way consistent with causality and unitarity. In case Sp(2,R) is a gauge symmetry, we show that the spacetime signature is determined dynamically as (D-2,2). The resulting noncommutative Sp(2,R) gauge theory is proposed as a field theoretical formulation of two-time physics: classical field dynamics contains all known results of `two-time physics', including the reduction of physical spacetime from D to (D-2) dimensions, with the associated `holography' and `duality' properties. In particular, we show that the solution space of classical noncommutative field equations put all massless scalar, gauge, gravitational, and higher-spin fields in (D-2) dimensions on equal-footing, reminiscent of string excitations at zero and infinite tension limits.Comment: 32 pages, LaTe

New Coherent String States and Minimal Uncertainty in WZWN Models

We study the properties of {\bf exact} (all level $k$) quantum coherent states in the context of string theory on a group manifold (WZWN models). Coherent states of WZWN models may help to solve the unitarity problem: Having positive norm, they consistently describe the very massive string states (otherwise excluded by the spin-level condition). These states can be constructed by (at least) two alternative procedures: (i) as the exponential of the creation operator on the ground state, and (ii) as eigenstates of the annhilation operator. In the $k\to\infty$ limit, all the known properties of ordinary coherent states are recovered. States (i) and (ii) (which are equivalent in the context of ordinary quantum mechanics and string theory in flat spacetime) are not equivalent in the context of WZWN models. The set (i) was constructed by these authors in a previous article. In this paper we provide the construction of states (ii), we compare the two sets and discuss their properties. We analyze the uncertainty relation, and show that states (ii) satisfy automatically the {\it minimal uncertainty} condition for any $k$; they are thus {\it quasiclassical}, in some sense more classical than states (i) which only satisfy it in the $k\to\infty$ limit. Modification to the Heisenberg relation is given by $2 {\cal H}/k$, where ${\cal H}$ is connected to the string energy.Comment: More discussion on relation to previous work. More references added. 14 pages, Latex, no figure

Local Conformal Symmetry in Physics and Cosmology

We show how to lift a generic non-scale-invariant action in Einstein frame into a locally conformally invariant (or Weyl-invariant) theory and present a new general form for Lagrangians consistent with Weyl symmetry. Advantages of such a conformally invariant formulation of particle physics and gravity include the possibility of constructing geodesically complete cosmologies. We present a conformal-invariant version of the standard model coupled to gravity, and show how Weyl symmetry may be used to obtain unprecedented analytic control over its cosmological solutions. Within this new framework, generic Friedmann-Robertson-Walker cosmologies are geodesically complete through a series of big crunch-big bang transitions. We discuss a new scenario of cosmic evolution driven by the Higgs field in a “minimal” conformal standard model, in which there is no new physics beyond the standard model at low energies, and the current Higgs vacuum is metastable as indicated by the latest LHC data

U*(1,1) Noncommutative Gauge Theory As The Foundation of 2T-Physics in Field Theory

A very simple field theory in noncommutative phase space X^{M},P^{M} in d+2 dimensions, with a gauge symmetry based on noncommutative u*(1,1), furnishes the foundation for the field theoretic formulation of Two-Time Physics. This leads to a remarkable unification of several gauge principles in d dimensions, including Maxwell, Einstein and high spin gauge principles, packaged together into one of the simplest fundamental gauge symmetries in noncommutative quantum phase space in d+2 dimensions. A gauge invariant action is constructed and its nonlinear equations of motion are analyzed. Besides elegantly reproducing the first quantized worldline theory with all background fields, the field theory prescribes unique interactions among the gauge fields. A matrix version of the theory, with a large N limit, is also outlinedComment: 24 pages, LaTe

On zero modes of the eleven dimensional superstring

It is shown that recently pointed out by Berkovits on-shell degrees of freedom of the D=11 superstring do not make contributions into the quantum states spectrum of the theory. As a consequence, the spectrum coincides with that of the D=10 type IIA superstring.Comment: 7 pages, LaTex fil