Walking in the SU(N)

We study the phase diagram as function of the number of colours and flavours of asymptotically free non-supersymmetric theories with matter in higher dimensional representations of arbitrary SU(N) gauge groups. Since matter in higher dimensional representations screens more than in the fundamental a general feature is that a lower number of flavours is needed to achieve a near-conformal theory. We study the spectrum of the theories near the fixed point and consider possible applications of our analysis to the dynamical breaking of the electroweak symmetry.Comment: 12 page

Light Composite Higgs from Higher Representations versus Electroweak Precision Measurements -- Predictions for LHC

We investigate theories in which the technifermions in higher dimensional representations of the technicolor gauge group dynamically break the electroweak symmetry of the standard model. For the two-index symmetric representation of the gauge group the lowest number of techniflavors needed to render the underlying gauge theory quasi conformal is two. We confront the models with the recent electroweak precision measurements and demonstrate that the two technicolor theory is a valid candidate for a dynamical breaking of the electroweak symmetry. The electroweak precision measurements provide useful constraints on the relative mass splitting of the new leptons needed to cure the Witten anomaly. In the case of a fourth family of leptons with ordinary lepton hypercharge the new heavy neutrino can be a natural candidate of cold dark matter. We also propose theories in which the critical number of flavors needed to enter the conformal window is higher than the one with fermions in the two-index symmetric representation, but lower than in the walking technicolor theories with fermions only in the fundamental representation of the gauge group. Due to the near conformal/chiral phase transition, we show that the composite Higgs is very light compared to the intrinsic scale of the technicolor theory. For the two technicolor theory we predict the composite Higgs mass not to exceed 150 GeV.Comment: RevTex, 53 pages, 7 figures and two table

Composite Higgs to two Photons and Gluons

We introduce a simple framework to estimate the composite Higgs boson coupling to two-photon in Technicolor extensions of the standard model. The same framework allows us to predict the composite Higgs to two-gluon process. We compare the decay rates with the standard model ones and show that the corrections are typically of order one. We suggest, therefore, that the two-photon decay process can be efficiently used to disentangle a light composite Higgs from the standard model one. We also show that the Tevatron results for the gluon-gluon fusion production of the Higgs either exclude the techniquarks to carry color charges to the 95% confidence level, if the composite Higgs is light, or that the latter must be heavier than around 200 GeV.Comment: RevTex 7 pages, 6 figure

Anomaly induced QCD potential and Quark Decoupling

We explore the anomaly induced effective QCD meson potential in the framework of the effective Lagrangian approach. We suggest a decoupling procedure, when a flavored quark becomes massive, which mimics the one employed by Seiberg for supersymmetric gauge theories. It is seen that, after decoupling, the QCD potential naturally converts to the one with one less flavor. We study the $N_c$ and $N_f$ dependence of the $\eta^{\prime}$ mass.Comment: 11 pages, RevTe

Opening the Window for Technicolor

Recently a new class of technicolor models are proposed, using technifermions of symmetric second-rank tensor. In the models, one can make reasonable estimates of physical quantities like the Higgs mass and the size of oblique corrections, using a correspondence to super Yang-Mills theory in the Corrigan-Ramond limit. The models predict a surprisingly light Higgs of mass, $m_H=150\sim 500 {\rm GeV}$ and have naturally small $S$ parameter.Comment: 5 pages, to appear in PASCOS04 proceedings; minor changes in context and in reference

Excluding Light Asymmetric Bosonic Dark Matter

We argue that current neutron star observations exclude asymmetric bosonic non-interacting dark matter in the range from 2 keV to 16 GeV, including the 5-15 GeV range favored by DAMA and CoGeNT. If bosonic WIMPs are composite of fermions, the same limits apply provided the compositeness scale is higher than ~10^12 GeV (for WIMP mass ~1 GeV). In case of repulsive self-interactions, we exclude large range of WIMP masses and interaction cross sections which complements the constraints imposed by observations of the Bullet Cluster.Comment: published versio

Anomaly Matching in Gauge Theories at Finite Matter Density

We investigate the application of 't Hooft's anomaly matching conditions to gauge theories at finite matter density. We show that the matching conditions constrain the low-energy quasiparticle spectrum associated with possible realizations of global symmetries.Comment: 11 pages, 1 figure, LaTeX. Section C is corrected and added reference

Light Asymmetric Dark Matter on the Lattice: SU(2) Technicolor with Two Fundamental Flavors

The SU(2) gauge theory with two massless Dirac flavors constitutes the building block of several models of Technicolor. Furthermore it has also been used as a template for the construction of a natural light asymmetric, or mixed type, dark matter candidate. We use explicit lattice simulations to confirm the pattern of chiral symmetry breaking by determining the Goldstone spectrum and therefore show that the dark matter candidate can, de facto, be constituted by a complex Goldstone boson. We also determine the phenomenologically relevant spin-one and spin-zero isovector spectrum and demonstrate that it is well separated from the Goldstone spectrum.Comment: 22 pages, 8 figures, published versio

Visibility graphs for fMRI data: Multiplex temporal graphs and their modulations across resting-state networks.

Visibility algorithms are a family of methods that map time series into graphs, such that the tools of graph theory and network science can be used for the characterization of time series. This approach has proved a convenient tool, and visibility graphs have found applications across several disciplines. Recently, an approach has been proposed to extend this framework to multivariate time series, allowing a novel way to describe collective dynamics. Here we test their application to fMRI time series, following two main motivations, namely that (a) this approach allows vs to simultaneously capture and process relevant aspects of both local and global dynamics in an easy and intuitive way, and (b) this provides a suggestive bridge between time series and network theory that nicely fits the consolidating field of network neuroscience. Our application to a large open dataset reveals differences in the similarities of temporal networks (and thus in correlated dynamics) across resting-state networks, and gives indications that some differences in brain activity connected to psychiatric disorders could be picked up by this approach