Breaking Discrete Symmetries in Broken Gauge Theories

We study the spontaneous breaking of discrete symmetries in theories with broken gauge symmetry. The intended application is to CP breaking in theories with gauged flavor symmetries, but the analysis described here is preliminary. We dispense with matter fields and take the gauge theory to be weakly coupled and broken spontaneously by unspecified, short-distance forces. We develop an effective-field-theory description of the resultant low energy theory, and ask whether this theory by itself can describe the subsequent breaking of discrete symmetries. We conclude that this can happen depending on the parameters of the effective theory, and that the intrinsic violation is naturally of order unity.Comment: 9 pages, 1 figure, corrected typos, added a referenc

Flavor-Changing Processes in Extended Technicolor

We analyze constraints on a class of extended technicolor (ETC) models from neutral flavor-changing processes induced by (dimension-six) four-fermion operators. The ETC gauge group is taken to commute with the standard-model gauge group. The models in the class are distinguished by how the left- and right-handed $(L,R)$ components of the quarks and charged leptons transform under the ETC group. We consider $K^{0} - \bar K^0$ and other pseudoscalar meson mixings, and conclude that they are adequately suppressed if the $L$ and $R$ components of the relevant quarks are assigned to the same (fundamental or conjugate-fundamental) representation of the ETC group. Models in which the $L$ and $R$ components of the down-type quarks are assigned to relatively conjugate representations, while they can lead to realistic CKM mixing and intra-family mass splittings, do not adequately suppress these mixing processes. We identify an approximate global symmetry that elucidates these behavioral differences and can be used to analyze other possible representation assignments. Flavor-changing decays, involving quarks and/or leptons, are adequately suppressed for any ETC-representation assignment of the $L$ and $R$ components of the quarks, as well as the leptons. We draw lessons for future ETC model building.Comment: 25 page

The fifth dimension as an analogue computer for strong interactions at the LHC

We present a mechanism to get S ~ 0 or even negative, without bringing into play the SM fermion sector. This mechanism can be applied to a wide range of 5D models, including composite Higgs and Higgsless models. As a realization of the mechanism we introduce a simple model, although the effect on S does not rely on the underlying dynamics generating the background. Models that include this mechanism enjoy the following features: weakly-coupled light resonances (as light as 600 GeV) and degenerate or inverted resonance spectrum.Comment: JHEP version. References adde

Chondroitin sulfate immobilization at the surface of electrospun nanofiber meshes for cartilage regeneration

Aiming at improving the biocompatibility of biomaterial scaffolds, surface modification presents a way to preserve their mechanical properties and to improve the surface bioactivity. In this work, chondroitin sulfate (CS) was immobilized at the surface of electrospun poly(caprolactone) nanofiber meshes (PCL NFMs). The immobilization was performed with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS). Contact Angle, SEM, Optical Profilometry, FTIR, X-ray photoelectron spectroscopy techniques confirmed the CS-immobilization in PCL NFMs. Furthermore, CS-immobilized PCL NFMs showed lower roughness and higher hydrophilicity than the samples without CS. Human articular chondrocytes (HACs) were cultured on electrospun PCL NFMs with or without CS immobilization. It was observed that HACs proliferated through the entire time course of the experiment in both types of scaffolds. SEM observations revealed that HACs maintained their typical morphology and produced extracellular matrix. Glycosaminoglycans quantification showed increased values over time. Quantitative-PCR of cartilage-related genes revealed over-expression of Aggrecan, Collagen type II, COMP and Sox9 on both types of NFMs tested, with higher values for PCL. In conclusion, CS immobilization in PCL NFM was achieved successfully and provides a valid platform enabling further surface functionalization methods in scaffolds to be developed for cartilage tissue engineering

Little Technicolor

Inspired by the AdS/CFT correspondence, we show that any G/H symmetry breaking pattern can be described by a simple two-site moose diagram. This construction trivially reproduces the CCWZ prescription in the context of Hidden Local Symmetry. We interpret this moose in a novel way to show that many little Higgs theories can emerge from ordinary chiral symmetry breaking in scaled-up QCD. We apply this reasoning to the simple group little Higgs to see that the same low energy degrees of freedom can arise from a variety of UV complete theories. We also show how models of holographic composite Higgs bosons can turn into brane-localized little technicolor theories by "integrating in" the IR brane.Comment: 26 pages, 2 figures; v2: references added; v3: added section on vacuum alignment to match JHEP versio

Towards multi-scale dynamics on the baryonic branch of Klebanov-Strassler

We construct explicitly a new class of backgrounds in type-IIB supergravity which generalize the baryonic branch of Klebanov-Strassler. We apply a solution-generating technique that, starting from a large class of solutions of the wrapped-D5 system, yields the new solutions, and then proceed to study in detail their properties, both in the IR and in the UV. We propose a simple intuitive field theory interpretation of the rotation procedure and of the meaning of our new solutions within the Papadopoulos-Tseytlin ansatz, in particular in relation to the duality cascade in the Klebanov-Strassler solution. The presence in the field theory of different VEVs for operators of dimensions 2, 3 and 6 suggests that this is an important step towards the construction of the string dual of a genuinely multi-scale (strongly coupled) dynamical model.Comment: 37 pages, 7 figures. References added, version to appear in JHE

Cancellation of Global Anomalies in Spontaneously Broken Gauge Theories

We discuss the generalization to global gauge anomalies of the familiar procedure for the cancellation of local gauge anomalies in effective theories of spontaneously broken symmetries. We illustrate this mechanism in a recently proposed six-dimensional extension of the standard model.Comment: 5 pages; v2: version to appear in Phys. Rev.

Symmetry restoration at high-temperature in two-color and two-flavor lattice gauge theories

We consider the SU(2) gauge theory with Nf=2 flavors of Dirac fundamental fermions. We study the high-temperature behavior of the spectra of mesons, discretizing the theory on anisotropic lattices, and measuring the two-point correlation functions in the temporal direction as well as screening masses in various channels. We identify the (pseudo-)critical temperature as the temperature at which the susceptibility associated with the Polyakov loop has a maximum. At high temperature both the spin-1 and spin-0 sectors of the light meson spectra exhibit enhanced symmetry properties, indicating the restoration of both the global SU(4) and the axial U(1)A symmetries of the model