3,279 research outputs found
A Perturbative Realization of Miransky Scaling
Near conformal dynamics is employed in different extensions of the standard
model of particle interactions as well as in cosmology. Many of its interesting
properties are either conjectured or determined using model computations. We
introduce a relevant four dimensional gauge theory template allowing us to
investigate such dynamics perturbatively. The gauge theory we consider is
quantum chromodynamics with the addition of a meson-like scalar degree of
freedom as well as an adjoint Weyl fermion.
At the two-loop level, and in the Veneziano limit, we firmly establish the
existence of several fixed points of which one is all directions stable in the
infrared. An interesting feature of the model is that this fixed point is lost,
within the perturbatively trustable regime, by merging with another fixed point
when varying the number of quark flavors. We show the emergence of the Miransky
scaling and determine its properties. We are also able to determine the walking
region of the theory which turns out to be, at large number of colors, about
12% of the conformal window. Furthermore, we determine highly relevant
quantities for near conformal dynamics such as the anomalous dimension of the
fermion masses.Comment: 17 pages, 8 figure
Confinement and Chiral Symmetry
We illustrate why color deconfines when chiral symmetry is restored in gauge
theories with quarks in the fundamental representation, and while these
transitions do not need to coincide when quarks are in the adjoint
representation, entanglement between them is still present.Comment: 4 pages, 1 figure, proceedings of Quark Matter 200
Technicolor Models with Color-Singlet Technifermions and their Ultraviolet Extensions
We study technicolor models in which all of the technifermions are
color-singlets, focusing on the case in these fermions transform according to
the fundamental representation of the technicolor gauge group. Our analysis
includes a derivation of restrictions on the weak hypercharge assignments for
the technifermions and additional color-singlet, technisinglet fermions arising
from the necessity of avoiding stable bound states with exotic electric
charges. Precision electroweak constraints on these models are also discussed.
We determine some general properties of extended technicolor theories
containing these technicolor sectors.Comment: 17 pages, latex, 2 figure
Gravitational Techniwaves
We investigate the production and possible detection of gravitational waves
stemming from the electroweak phase transition in the early universe in models
of minimal walking technicolor. In particular we discuss the two possible
scenarios in which one has only one electroweak phase transition and the case
in which the technicolor dynamics allows for multiple phase transitions.Comment: 30 pages, 5 figures. v2: minor changes, references added, title
changed in journa
Logarithmic correction in the deformed model to produce the heavy quark potential and QCD beta function
We stude the \textit{holographic} QCD model which contains a quadratic term and a logarithmic term with an
explicit infrared cut-off in the deformed warp factor.
We investigate the heavy quark potential for three cases, i.e, with only
quadratic correction, with both quadratic and logarithmic corrections and with
only logarithmic correction. We solve the dilaton field and dilation potential
from the Einstein equation, and investigate the corresponding beta function in
the G{\"u}rsoy -Kiritsis-Nitti (GKN) framework. Our studies show that in the
case with only quadratic correction, a negative or the
Andreev-Zakharov model is favored to fit the heavy quark potential and to
produce the QCD beta-function at 2-loop level, however, the dilaton potential
is unbounded in infrared regime. One interesting observing for the case of
positive , or the soft-wall model is that the
corresponding beta-function exists an infrared fixed point. In the case with
only logarithmic correction, the heavy quark Cornell potential can be fitted
very well, the corresponding beta-function agrees with the QCD beta-function at
2-loop level reasonably well, and the dilaton potential is bounded from below
in infrared. At the end, we propose a more compact model which has only
logarithmic correction in the deformed warp factor and has less free
parameters.Comment: 24 pages, 16 figure
The Electroweak Phase Transition in Ultra Minimal Technicolor
We unveil the temperature-dependent electroweak phase transition in new
extensions of the Standard Model in which the electroweak symmetry is
spontaneously broken via strongly coupled, nearly-conformal dynamics achieved
by the means of multiple matter representations. In particular, we focus on the
low energy effective theory introduced to describe Ultra Minimal Walking
Technicolor at the phase transition. Using the one-loop effective potential
with ring improvement, we identify regions of parameter space which yield a
strong first order transition. A striking feature of the model is the existence
of a second phase transition associated to the electroweak-singlet sector. The
interplay between these two transitions leads to an extremely rich phase
diagram.Comment: 38 RevTeX pages, 9 figure
Technicolor and Beyond: Unification in Theory Space
The salient features of models of dynamical electroweak symmetry breaking are
reviewed. The ideal walking idea is introduced according to which one should
carefully take into account the effects of the extended technicolor dynamics on
the technicolor dynamics itself. The effects amount at the enhancement of the
anomalous dimension of the mass of the techniquarks allowing to decouple the
Flavor Changing Neutral Currents problem from the one of the generation of the
top mass. Precision data constraints are reviewed focussing on the latest
crucial observation that the S-parameter can be computed exactly near the upper
end of the conformal window (Conformal S-parameter) with relevant consequences
on the selection of nature's next strong force. We will then introduce the
Minimal Walking Technicolor (MWT) models. In the second part of this review we
consider the interesting possibility to marry supersymmetry and technicolor.
The reason is to provide a unification of different extensions of the standard
model. For example, this means that one can recover, according to the
parameters and spectrum of the theory distinct extensions of the standard
model, from supersymmetry to technicolor and unparticle physiscs. A surprising
result is that a minimal (in terms of the smallest number of fields)
supersymmetrization of the MWT model leads to the maximal supersymmetry in four
dimensions, i.e. N=4 SYM.Comment: Extended version of the PASCOS10 proceedings for the Plenary Tal
Extending the Veneziano-Yankielowicz Effective Theory
We extend the Veneziano Yankielowicz (VY) effective theory in order to
account for ordinary glueball states. We propose a new form of the
superpotential including a chiral superfield for the glueball degrees of
freedom. When integrating it ``out'' we obtain the VY superpotential while the
N vacua of the theory naturally emerge. This fact has a counterpart in the
Dijkgraaf and Vafa geometric approach. We suggest a link of the new field with
the underlying degrees of freedom which allows us to integrate it ``in'' the VY
theory. We finally break supersymmetry by adding a gluino mass and show that
the Kahler independent part of the ``potential'' has the same form of the
ordinary Yang-Mills glueball effective potential.Comment: LaTeX, 20 page
Comment on ``Confirmation of the Sigma Meson''
We comment on the recent paper by N.A. Tornqvist and M. Roos published in
Phys. Rev. Lett. 76, 1575 (1996).Comment: 3 pages (LaTeX), 1 PostScript Figur
Study of an Alternate Mechanism for the Origin of Fermion Generations
In usual extended technicolor (ETC) theories based on the group
, the quarks of charge 2/3 and -1/3 and the charged
leptons of all generations arise from ETC fermion multiplets transforming
according to the fundamental representation. Here we investigate a different
idea for the origin of SM fermion generations, in which quarks and charged
leptons of different generations arise from ETC fermions transforming according
to different representations of . Although this
mechanism would have the potential, {\it a priori}, to allow a reduction in the
value of relative to conventional ETC models, we show that, at least
in simple models, it is excluded by the fact that the technicolor sector is not
asymptotically free or by the appearance of fermions with exotic quantum
numbers which are not observed.Comment: 6 pages, late
- …