Semi-local Cosmic Strings and the Cosmological Constant Problem

We study the cosmological constant problem in a three-dimensional N=2 supergravity theory with gauge group SU[2]_{global}xU[1]_{local}. The model we consider is known to admit string-like configurations, the so-called semi-local cosmic strings. We show that the stability of these solutions is provided by supersymmetry through the existence of a lower bound for the energy, even though the manifold of the Higgs vacuum does not contain non-contractible loops. Charged Killing spinors do exist over configurations that saturate the Bogomolnyi bound, as a consequence of an Aharonov-Bohm-like effect. Nevertheless, there are no physical fermionic zero modes on these backgrounds. The exact vanishing of the cosmological constant does not imply, then, Bose-Fermi degeneracy. This provides a non-trivial example of the recent claim made by Witten on the vanishing of the cosmological constant in three dimensions without unphysical degeneracies.Comment: 12 pages, LaTeX. To appear in Physics Letters

The Function of Self-Consciousness in John Barth\u27s Chimera

Much recent American fiction has become increasingly self-conscious, displaying an awareness of itself as fiction, as artifice that diminishes the role of a central human consciousness or self in the fiction. The fictional process is in the foreground of much contemporary fiction where the narrative human presence once was. Yet, both fictional process and human presence serve similar structural functions within the text, which suggests that the creation of a fiction resembles the creation of a human self, real or imaginary. The provisional reality of self-conscious fiction is like the provisional reality of the post-modern self, prone to self-questioning, constituted by process rather than substance, multiple, changeable, perhaps even illusory. John Barth\u27s novel Chimera is a supremely self-conscious fiction. Barth\u27s use of the three central narrators in the three sections of the novel— the Dunyazadiad , the Perseid , and the Bellerophoniad — foregrounds the relationship between diffusion of identity and artistic self-consciousness within the novel. Although an individual, by definition, should not be susceptible to division or separation into parts without losing its identity, the narrators in Chimera, like the novel\u27s sections, are all divisible, incomplete, or inter-changeable. Definitions of identity often include elements such as continuity, functional unity, consciousness, récognitive memory, personality, or awareness. Yet, there is still a question about the relation of a self so constituted to se//-conscious fiction

BPS Solitons and Killing Spinors in Three Dimensional N=2 Supergravity

In the framework of three dimensional extended supergravity theories, we demonstrate that there exist non-trivial Killing spinors over BPS soliton configurations, even when the space-time is asymptotically conical. We also show that there are no physical fermionic zero modes on these backgrounds. We further generalize these results to the case of semilocal systems.Comment: 7 pages, LaTeX. Short Talk given at the Meeting ``Trends in Theoretical Physics'', April 28th-May 6th, 1997, La Plata, Argentin

Probe D-branes in Superconformal Field Theories

We overview the main configurations of D-brane probes in the AdS_5 x X^5 background of type IIB string theory (X^5 being a Sasaki-Einstein manifold), and examine their most salient features from the point of view of the dual quiver superconformal field theory.Comment: 5 pages; contribution to the proceedings of the 2nd RTN Network Workshop and Midterm Meeting: Constituents, Fundamental Forces and Symmetries of the Universe, Naples, Italy, 9-13 Oct 2006; v2: a footnote and a reference adde

Strong coupling expansion and Seiberg-Witten-Whitham equations

We study the Seiberg-Witten-Whitham equations in the strong coupling regime of the N=2 super Yang-Mills theory in the vicinity of the maximal singularities. In the case of SU(2) the Seiberg-Witten-Whitham equations fix completely the strong coupling expansion. For higher rank SU(N) they provide a set of non-trivial constraints on the form of this expansion. As an example, we study the off-diagonal couplings at the maximal point for which we propose an ansatz that fulfills all the equations.Comment: 10 pages, LaTeX, no figures; v2: The expression for the off-diagonal couplings has been corrected and numerical checks have been extended. One reference adde

Supersymmetry and Bosonization in Three Dimensions

We discuss on the possible existence of a supersymmetric invariance in purely fermionic planar systems and its relation to the fermion-boson mapping in three-dimensional quantum field theory. We consider, as a very simple example, the bosonization of free massive fermions and show that, under certain conditions on the masses, this model displays a supersymmetric-like invariance in the low energy regime. We construct the purely fermionic expression for the supercurrent and the non-linear supersymmetry transformation laws. We argue that the supersymmetry is absent in the limit of massless fermions where the bosonized theory is non-local.Comment: 12 pages, LaTeX, no figures, to appear in Physics Letters

D6 branes and M theory geometrical transitions from gauged supergravity

We study the supergravity duals of supersymmetric theories arising in the world-volume of D6 branes wrapping holomorphic two-cycles and special Lagrangian three-cycles within the framework of eight dimensional gauged supergravity. When uplifted to 11d, our solutions represent M-theory on the background of, respectively, the small resolution of the conifold and a manifold with G_2 holonomy. We further discuss on the flop and other possible geometrical transitions and its implications.Comment: 16 pages, harvmac, one figure; references adde

Was Adherence to the Gold Standard a "Good Housekeeping Seal of Approval" During the Interwar Period?

World War I dramatically altered the world's financial landscape. Most countries left the gold standard, and New York replaced London as the major lender in world capital markets. This paper discusses how the gold exchange standard was reconstructed in the 1920s. We show that the U.S. capital market viewed returning to the gold standard as a signal of financial rectitude, what we have referred to in other work as a 'Good Housekeeping Seal of Approval.' When countries returned to gold, especially when they did so at the prewar parity, they were rewarded with the ability to borrow at substantially lower interest rates. Other signals of financial rectitude, such as small fiscal deficits, apparently carried little weight with lenders.

N=2 supersymmetric Yang-Mills theories and Whitham integrable hierarchies

We review recent work on the study of N=2 super Yang-Mills theory with gauge group SU(N) from the point of view of the Whitham hierarchy, mainly focusing on three main results: (i) We develop a new recursive method to compute the whole instanton expansion of the low-energy effective prepotential; (ii) We interpret the slow times of the hierarchy as additional couplings and promote them to spurion superfields that softly break N=2 supersymmetry down to N=0 through deformations associated to higher Casimir operators of the gauge group; (iii) We show that the Seiberg-Witten-Whitham equations provide a set of non-trivial constraints on the form of the strong coupling expansion in the vicinity of the maximal singularities. We use them to check a proposal that we make for the value of the off-diagonal couplings at those points of the moduli space.Comment: 19 pages, LaTeX, no figures; Invited talk at the Second Meeting "Trends in Theoretical Physics", held in Buenos Aires, December 199