Inheritance principle and Non-renormalization theorems at finite temperature

We present a general proof of an ``inheritance principle'' satisfied by a weakly coupled SU(N) gauge theory with adjoint matter on a class of compact manifolds (like $S^3$). In the large $N$ limit, finite temperature correlation functions of gauge invariant single-trace operators in the low temperature phase are related to those at zero temperature by summing over images of each operator in the Euclidean time direction. As a consequence, various non-renormalization theorems of \NN=4 Super-Yang-Mills theory on $S^3$ survive at finite temperature despite the fact that the conformal and supersymmetries are both broken.Comment: 14 pages, uses harvmac v2: reference added, the role of hep-th/0505148 emphasize

Aspects of finite temperature field theories in Ads/CFT

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2008.Includes bibliographical references (p. 119-124).In this dissertation I study some properties of field theories at finite temperature using the AdS/CFT correspondence. I present a general proof of an "inheritance principle" satisfied by a weakly coupled SU(N) (or U(N)) gauge theory with adjoint matter on a class of compact manifolds (like S3). In the large N limit, finite temperature correlation functions of gauge invariant single-trace operators in the low temperature phase are related to those at zero temperature by summing over images of each operator in the Euclidean time direction. As a consequence, various non-renormalization theorems of Af = 4 Super Yang-Mills theory on S3 survive at finite temperature. I use the factorization of the worldsheet to isolate the Hagedorn divergences at all orders in the genus expansion and to show that the Hagedorn divergences can be re-summed by introducing double scaling limits. This allows one to extract the effective potential for the thermal scalar. For a string theory in an asymptotic anti-de Sitter (AdS) space time, the same behavior should arise from the boundary YangMills theory. Introducing "vortex" contributions for the boundary theory at finite temperature I will show that this is indeed the case and that Yang-Mills Feynman diagrams with vortices can be identified with contributions from boundaries of moduli space on the string theory side. Finally, I consider the shear viscosity to entropy density ratio in conformal field theories dual to Einstein gravity with curvature square corrections. For generic curvature square corrections I show that the conjectured viscosity bound can be violated. I present the calculation in three different methods in order to check consistency. Gauss-Bonnet gravity is also considered, for any value of the coupling. It is shown that a lower bound (lower than the KSS bound) on the shear viscosity to entropy density ratio is determined by causality in the boundary theory.by Mauro Brigante.Ph.D

Concept, prototyping and application of a tensioning system for FRP ties into masonry structures

The present paper deals with concept, prototyping and application of a tensioning system for FRP ties into masonry structures. The proposed system, based on the use of FRP strands instead of traditional steel ties, has the aim to produce a compression stress state on masonry walls where it is applied. Given the objective difficulty in tensioning a FRP strand, it has been necessary to both characterize and prototype a suitable connection system between the strand and the pulling system. The experimental phase concerned both the manufacturing of the pulling system and the study of used materials, as well as the characterization of the impregnation technology of FRP ties. The above described system has been produced and used in the framework of the structural retrofitting of the “Real Albergo dei Poveri” building in Naples

Viscosity Bound and Causality Violation

In recent work we showed that, for a class of conformal field theories (CFT) with Gauss-Bonnet gravity dual, the shear viscosity to entropy density ratio, $\eta/s$, could violate the conjectured Kovtun-Starinets-Son viscosity bound, $\eta/s\geq1/4\pi$. In this paper we argue, in the context of the same model, that tuning $\eta/s$ below $(16/25)(1/4\pi)$ induces microcausality violation in the CFT, rendering the theory inconsistent. This is a concrete example in which inconsistency of a theory and a lower bound on viscosity are correlated, supporting the idea of a possible universal lower bound on $\eta/s$ for all consistent theories.Comment: 5 pages, 2 figures; v2: a slight change in the title and minor revisions made, references update

Viscosity Bound Violation in Higher Derivative Gravity

Motivated by the vast string landscape, we consider the shear viscosity to entropy density ratio in conformal field theories dual to Einstein gravity with curvature square corrections. After field redefinitions these theories reduce to Gauss-Bonnet gravity, which has special properties that allow us to compute the shear viscosity nonperturbatively in the Gauss-Bonnet coupling. By tuning of the coupling, the value of the shear viscosity to entropy density ratio can be adjusted to any positive value from infinity down to zero, thus violating the conjectured viscosity bound. At linear order in the coupling, we also check consistency of four different methods to calculate the shear viscosity, and we find that all of them agree. We search for possible pathologies associated with this class of theories violating the viscosity bound.Comment: 23 pages, 2 figures; v2: typos corrected, references added, notes added; v3: subsections IV.C and IV.D eliminated, comments on the null energy condition eliminated, minor revisions mad

The Asymptotic Dynamics of two-dimensional (anti-)de Sitter Gravity

We show that the asymptotic dynamics of two-dimensional de Sitter or anti-de Sitter Jackiw-Teitelboim (JT) gravity is described by a generalized two-particle Calogero-Sutherland model. This correspondence is established by formulating the JT model of (A)dS gravity in two dimensions as a topological gauge theory, which reduces to a nonlinear 0+1-dimensional sigma model on the boundary of (A)dS space. The appearance of cyclic coordinates allows then a further reduction to the Calogero-Sutherland quantum mechanical model.Comment: 16 pages, LaTeX, no figures, uses JHEP.cls. v2: Some references and comments added. v3: Minor errors correcte

Hagedorn divergences and tachyon potential

We consider the critical behavior for a string theory near the Hagedorn temperature. We use the factorization of the worldsheet to isolate the Hagedorn divergences at all genera. We show that the Hagedorn divergences can be resummed by introducing double scaling limits, which smooth the divergences. The double scaling limits also allow one to extract the effective potential for the thermal scalar. For a string theory in an asymptotic anti-de Sitter (AdS) spacetime, the AdS/CFT correspondence implies that the critical Hagedorn behavior and the relation with the effective potential should also arise from the boundary Yang-Mills theory. We show that this is indeed the case. In particular we find that the free energy of a Yang-Mills theory contains ``vortex'' contributions at finite temperature. Yang-Mills Feynman diagrams with vortices can be identified with contributions from boundaries of moduli space on the string theory side.Comment: 36 pages, 13 figures, uses harvma

Comparative Safety of Originator and Biosimilar Epoetin Alfa Drugs: An Observational Prospective Multicenter Study

Background: Erythropoiesis-stimulating agents (ESAs) are biological molecules approved for the treatment of anemia associated with chronic renal failure. Biosimilars were licensed for use in Europe in 2007. Aim: This study aimed to compare the safety profile of biosimilars with respect to the reference product in a nephrology setting. Methods: A prospective study was conducted in four Italian regions between 1 October 2013 and 30 June 2015. The study population included patients aged 65 18 years undergoing hemodialysis and treated with epoetins as per the clinical practice of the participating centers. The two comparison cohorts included patients treated with either an originator or a biosimilar epoetin alfa. Each patient was followed up until occurrence of any safety outcome of interest (grouped into three major categories), switch to a different ESA product, transplant or peritoneal dialysis, death, or end of the study period, whichever came first. Results: Overall, 867 subjects were included in the study (originator: N = 423; biosimilar: N = 444). Biosimilar users were older than originator users (median age of 76 vs 64 years, respectively), more frequently affected by arrhythmia (29.3 vs 22.5%), and less frequently candidates for transplantation (3.8 vs 18.2%). Cox-regression analysis showed no increase in risk of safety outcomes in biosimilar users, even after adjusting for confounding factors: 1.0 (95% confidence interval [CI] 0.7\u20131.3) for any outcomes; 1.1 (95% CI 0.7\u20131.8) for problems related to dialysis device; 0.9 (95% CI 0.6\u20131.5) for cardio- and cerebro-vascular conditions; 0.9 (95% CI 0.6\u20131.5) for infections. Conclusion: This study confirms the comparable safety profiles of originator and biosimilar epoetin alfa drugs when used in patients receiving dialysis