On supersymmetry breaking and the Dijkgraaf-Vafa conjecture

We investigate the Dijkgraaf-Vafa proposal when supersymmetry is broken. We consider U(N) SYM with chiral adjoint matter where the coupling constants in the tree-level superpotential are promoted to chiral spurions. The holomorphic part of the low-energy glueball superpotential can still be analyzed. We compute the holomorphic supersymmetry breaking contributions using methods of the geometry underlying the N=1 effective gauge theory viewed as a Whitham system. We also study the change in the effective glueball superpotential using perturbative supergraph techniques in the presence of spurions.Comment: 24 pages, LaTeX; minor changes, one reference added, version to appear in JHE

D-Brane Interactions in a Gravitational Shock Wave Background

We study D-branes in the background of a gravitational shock wave. We consider the case of parallel D-branes located on opposite sides with respect to the shock wave. Their interaction is studied by evaluating the cylinder diagram using the boundary states technique. Boundary states are defined at each D-brane and their scalar product is evaluated after propagation through the shock wave. Taking the limit where the gravitational shock wave vanishes we show that the amplitude evaluated is consistent with the flat space-time result.Comment: To be published in Modern Physics Letters A, revised version with references added, 12 page

A universal flow invariant in quantum field theory

A flow invariant is a quantity depending only on the UV and IR conformal fixed points and not on the flow connecting them. Typically, its value is related to the central charges a and c. In classically-conformal field theories, scale invariance is broken by quantum effects and the flow invariant a_{UV}-a_{IR} is measured by the area of the graph of the beta function between the fixed points. There exists a theoretical explanation of this fact. On the other hand, when scale invariance is broken at the classical level, it is empirically known that the flow invariant equals c_{UV}-c_{IR} in massive free-field theories, but a theoretical argument explaining why it is so is still missing. A number of related open questions are answered here. A general formula of the flow invariant is found, which holds also when the stress tensor has improvement terms. The conditions under which the flow invariant equals c_{UV}-c_{IR} are identified. Several non-unitary theories are used as a laboratory, but the conclusions are general and an application to the Standard Model is addressed. The analysis of the results suggests some new minimum principles, which might point towards a better understanding of quantum field theory.Comment: 28 pages, 3 figures; proof-corrected version for CQ

The Three Dimensional Dual of 4D Chirality

Chiral gauge theories can be defined in four-dimensional Anti de Sitter space, but AdS boundary conditions explicitly break the chiral symmetry in a specific, well defined manner, which in turns results in an anomalous Ward identity. When the 4D theory admits a dual description in terms of a 3D CFT, the 3D dual of the broken chiral symmetry is a certain double-trace deformation of the CFT, which produces the same anomalous chiral Ward identities that obtains in the 4D bulk theory.Comment: 10 pages, small misprints corrected, reference [16] updated. Version to appear in JHE

Hirudo medicinalis as alternative model for in vivo and in vitro studies on nanomaterials toxicity.

Due to the steady increase of production and use of engineered nanomaterials (NMs), intentional or unintentional discharges into the environment may occur. Since it is critical to develop new methods to fully understand NMs bioaccumulation and cytotoxicity, a reliable model in which analyze NMs effects both in vivo and in vitro is more than ever necessary. Here we propose the leech, Hirudo medicinalis, as alternative animal model to study multi-walled carbon nanotubes (MWCNTs) effects by means of an extended study that includes in vivo and in vitro treatments. First, MWCNTs were dispersed in leeches\u2019 water to mimic a possible environmental exposure. In a second assay, a MWCNTs-supplemented biomatrix was injected in leeches\u2019 body wall. Thirdly, leeches macrophages were isolated and cultured to analyze their responses after MWCNTs in vitro treatment. Our results show that water dispersed MWCNTs evoke in the leech body wall a strong inflammatory response, involving mainly monocyte-macrophages cells. Ultrastructural analysis of MWCNTs-supplemented biomatrix revealed that in leech macrophages MWCNTs are internalized both in an active (phagocytosis) and a passive manner (membrane piercing). Finally, MWCNTs in vitro treatment cause the decrease of cell proliferation rate and the increase of ROS production and of the apoptotic rate. Our combined experimental approaches, not only attest the ability of MWCNTs in inducing a potent inflammatory response, but also confirm Hirudo medicinalis as a good alternative model that can be successfully used to study, both in vivo and in vitro, the possible harmful effects of any nanomaterial

Renormalization Group Flows from Five-Dimensional Supergravity

The use of gauged ${\cal N} = 8$ supergravity as a tool in studying the AdS/CFT correspondence for ${\cal N} = 4$ Yang-Mills theory is reviewed. The supergravity potential implies a non-trivial, supersymmetric IR fixed point, and the flow to this fixed point is described in terms of a supergravity kink. The results agree perfectly with earlier, independent field theory results. A supergravity inspired $c$-function, and corresponding $c$-theorem is discussed for general flows, and the simplified form for supersymmetric flows is also given. Flows along the Coulomb branch of the Yang-Mills theory are also described from the five-dimensional perspective.Comment: 12 pages, 3 figures; Latex, ioplppt.sty, iopl12.sty, epsf.sty. Contribution to Strings `9

Higher derivative corrections in holographic Zamolodchikov-Polchinski theorem

We study higher derivative corrections in holographic dual of Zamolodchikov-Polchinski theorem that states the equivalence between scale invariance and conformal invariance in unitary d-dimensional Poincare invariant field theories. From the dual holographic perspective, we find that a sufficient condition to show the holographic theorem is the generalized strict null energy condition of the matter sector in effective (d+1)-dimensional gravitational theory. The same condition has appeared in the holographic dual of the "c-theorem" and our theorem suggests a deep connection between the two, which was manifested in two-dimensional field theoretic proof of the both.Comment: 13 pages, v2: reference added, v3 some clarification adde

BPS equations in N=2, D=5 supergravity with hypermultiplets

With the general aim to classify BPS solutions in N=2, D=5 supergravities interacting with an arbitrary number of vector, tensor and hypermultiplets, here we begin considering the most general electrostatic, spherical-symmetric BPS solutions in the presence of hypermultiplet couplings. We discuss the properties of the BPS equations and the restrictions imposed by their integrability conditions. We exhibit explicit solutions for the case of static BPS black-holes coupled to one (the so called universal) hypermultiplet.Comment: 20 pages, v3 some corrections performed; we thank A.Van Proeyen for the pointing ou

Yang-Mills theory from non-critical string

The correspondence of the non-critical string theory and the Yang-Mills theory is examined according to the recent Polyakov's proposal, and two possible solutions of the bulk equations are addressed near the fixed points of the pure Yang-Mills theory: (i) One solution asymptotically approaches to the AdS space at the ultraviolet limit where the conformally invariant field theory is realized. (ii) The second one approaches to the flat space in both the infrared and the ultraviolet limits. The area law of the Wilson-loop and the asymptotic freedom with logarithmic behaviour are seen in the respective limit.Comment: 17 pages, no figure, Late

Non-conformal examples of AdS/CFT

Asymptotically anti-de Sitter spacetimes with Poincare invariance along the boundary can describe, via the AdS/CFT correspondence, either relevant deformations of a conformal field theory or non-conformal vacuum states. I consider examples of both types constructed in the framework of five-dimensional gauged supergravity. I explain the proof and motivation of a gravitational ``c-theorem'' which is independent of dimension. I show how one class of examples can be elevated to ten-dimensional geometries involving distributions of parallel D3-branes. For these cases some peculiar properties of two-point functions emerge, and I close with speculations on their physical origin.Comment: 16 pages, two figures, latex. Strings '99 tal