Quantum Stability of the Phase Transition in Rigid QED

Rigid QED is a renormalizable generalization of Feynman's space-time action characterized by the addition of the curvature of the world line (rigidity). We have recently shown that a phase transition occurs in the leading approximation of the large N limit. The disordered phase essentially coincides with ordinary QED, while the ordered phase is a new theory. We have further shown that both phases of the quantum theory are free of ghosts and tachyons. In this letter, we study the first sub-leading quantum corrections leading to the renormalized mass gap equation. Our main result is that the phase transition does indeed survive these quantum fluctuations.Comment: PHYZZX, 9 pages, 3 Postscript figures, to be published in Nucl. Phys.

Renormalizability and Quantum Stability of the Phase Transition in Rigid String Coupled to Kalb-Ramond Fields II

Recently we have shown that a phase transition occurs in the leading approximation of the large N limit in rigid strings coupled to long range Kalb-Ramond interactions. The disordered phase is essentially the Nambu-Goto-Polyakov string theory while the ordered phase is a new theory. In this part II letter we study the first sub-leading quantum corrections we started in I. We derive the renormalized mass gap equation and obtain the renormalized critical line of the interacting theory. Our main and final result is that the phase transition does indeed survive quantum fluctuations.Comment: PHYZZX, 11 pages, 2 Postscript figure, to be published in Nucl.Phys.

Dimensionless Coupling of Superstrings to Supersymmetric Gauge Theories and Scale Invariant Superstring Actions

We construct new superstring actions which are distinguished from standard superstrings by being space-time scale invariant. Like standard superstrings, they are also reparametrization invariant, space-time supersymmetric, and invariant under local scale transformations of the world sheet. We discuss scenarios in which these actions could play a significant role, in particular one which involves their coupling to supersymmetric gauge theories.Comment: 9 pages, LaTe

L-branes

The superembedding approach to $p$-branes is used to study a class of $p$-branes which have linear multiplets on the worldvolume. We refer to these branes as L-branes. Although linear multiplets are related to scalar multiplets (with 4 or 8 supersymmetries) by dualising one of the scalars of the latter to a $p$-form field strength, in many geometrical situations it is the linear multiplet version which arises naturally. Furthermore, in the case of 8 supersymmetries, the linear multiplet is off-shell in contrast to the scalar multiplet. The dynamics of the L-branes are obtained by using a systematic procedure for constructing the Green-Schwarz action from the superembedding formalism. This action has a Dirac-Born-Infeld type structure for the $p$-form. In addition, a set of equations of motion is postulated directly in superspace, and is shown to agree with the Green-Schwarz equations of motion.Comment: revised version, minor changes, references added, 22 pages, no figures, LaTe

M-Theory on (K3 X S^1)/Z_2

We analyze $M$-theory compactified on $(K3\times S^1)/Z_2$ where the $Z_2$ changes the sign of the three form gauge field, acts on $S^1$ as a parity transformation and on K3 as an involution with eight fixed points preserving SU(2) holonomy. At a generic point in the moduli space the resulting theory has as its low energy limit N=1 supergravity theory in six dimensions with eight vector, nine tensor and twenty hypermultiplets. The gauge symmetry can be enhanced (e.g. to $E_8$) at special points in the moduli space. At other special points in the moduli space tensionless strings appear in the theory.Comment: LaTeX file, 11 page

Matter Fields in the Lagrangian Loop Representation: Scalar QED

We present the extension of the Lagrangian loop gauge invariant representation in such a way to include matter fields. The partition function of lattice compact U(1)-Higgs model is expressed as a sum over closed as much as open surfaces. We have simulated numerically the loop action equivalent to the Villain form of the action and mapped out the beta-gamma phase diagram of this model.Comment: 10 pages, LaTe

Supersymmetric AdS vacua and separation of scales

The moduli space of the supersymmetric massive IIA AdS4xS2(B4) vacua, where S2(B4) is a two-sphere bundle over a four-dimensional Kaehler-Einstein base B4, includes three independent parameters which can be thought of as corresponding to the sizes of AdS4, B4 and the S2 fiber. It might therefore be expected that these vacua do not suffer from the absence of scale separation. We show that the independence of the geometric moduli survives flux quantization. However, we uncover an attractor behavior whereby all sizes flow to equality in some neighborhood of spacetime independently of the initial conditions set by the parameters of the solution. This is further confirmed by the study of the ratio of internal to external scalar curvatures. We also show that the asymptotic Kaluza-Klein spectrum of a ten-dimensional massive scalar is governed by a scale of the order of the AdS4 radius. Furthermore we point out that the curvature ratio in supersymmetric IIA AdS4 vacua with rigid SU(3) structure is of order one, indicating the absence of scale separation in this large class of vacua.Comment: 21 pages, 2 figures; v2 typos correcte