3,093 research outputs found
Supersymmetry Inspired QCD Beta Function
We propose an all orders beta function for ordinary Yang-Mills theories with
or without fermions inspired by the Novikov-Shifman-Vainshtein-Zakharov beta
function of N=1 supersymmetric gauge theories. The beta function allows us to
bound the conformal window. When restricting to one adjoint Weyl fermion we
show how the proposed beta function matches the one of supersymmetric
Yang-Mills theory. The running of the pure Yang-Mills coupling is computed and
the deviation from the two loop result is presented. We then compare the
deviation with the one obtained from lattice data also with respect to the two
loop running.Comment: 17 pages and 3 figures. References Adde
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 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
Density of states and Fisher's zeros in compact U(1) pure gauge theory
We present high-accuracy calculations of the density of states using
multicanonical methods for lattice gauge theory with a compact gauge group U(1)
on 4^4, 6^4 and 8^4 lattices. We show that the results are consistent with weak
and strong coupling expansions. We present methods based on Chebyshev
interpolations and Cauchy theorem to find the (Fisher's) zeros of the partition
function in the complex beta=1/g^2 plane. The results are consistent with
reweighting methods whenever the latter are accurate. We discuss the volume
dependence of the imaginary part of the Fisher's zeros, the width and depth of
the plaquette distribution at the value of beta where the two peaks have equal
height. We discuss strategies to discriminate between first and second order
transitions and explore them with data at larger volume but lower statistics.
Higher statistics and even larger lattices are necessary to draw strong
conclusions regarding the order of the transition.Comment: 14 pages, 16 figure
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
A study of the influence of the gauge group on the Dyson-Schwinger equations for scalar-Yang-Mills systems
The particular choice of the gauge group for Yang-Mills theory plays an
important role when it comes to the influence of matter fields. In particular,
both the chosen gauge group and the representation of the matter fields yield
structural differences in the quenched case. Especially, the qualitative
behavior of the Wilson potential is strongly dependent on this selection.
Though the algebraic reasons for this observation is clear, it is far from
obvious how this behavior can be described besides using numerical simulations.
Herein, it is investigated how the group structure appears in the
Dyson-Schwinger equations, which as a hierarchy of equations for the
correlation functions have to be satisfied. It is found that there are
differences depending on both the gauge group and the representation of the
matter fields. This provides insight into possible truncation schemes for
practical calculations using these equations.Comment: 47 page
Polyakov Loops versus Hadronic States
The order parameter for the pure Yang-Mills phase transition is the Polyakov
loop which encodes the symmetries of the Z_N center of the SU(N) gauge group.
On the other side the physical degrees of freedom of any asymptotically free
gauge theory are hadronic states. Using the Yang-Mills trace anomaly and the
exact Z_N symmetry we construct a model able to communicate to the hadrons the
information carried by the order parameter.Comment: RevTex4 2-col., 6 pages, 2 figures. Typos fixed and added a paragraph
in the conclusion
Induced Universal Properties and Deconfinement
We propose a general strategy to determine universal properties induced by a
nearby phase transition on a non-order parameter field. A general
renormalizable Lagrangian is used, which contains the order parameter and a
non-order parameter field, and respects all the symmetries present. We
investigate the case in which the order parameter field depends only on space
coordinates and the case in which this field is also time dependent. We find
that the spatial correlators of the non-order parameter field, in both cases,
are infrared dominated and can be used to determine properties of the phase
transition. We predict a universal behavior for the screening mass of a generic
singlet field, and show how to extract relevant information from such a
quantity. We also demonstrate that the pole mass of the non-order parameter
field is not infrared sensitive. Our results can be applied to any continuous
phase transition. As an example we consider the deconfining transition in pure
Yang-Mills theory, and show that our findings are supported by lattice data.
Our analysis suggests that monitoring the spatial correlators of different
hadron species, more specifically the derivatives of these, provides an
efficient and sufficient way to experimentally uncover the deconfining phase
transition and its features.Comment: Added computational details and improved the text. The results are
unchange
Scaling laws near the conformal window of many-flavor QCD
We derive universal scaling laws for physical observables such as the
critical temperature, the chiral condensate, and the pion decay constant as a
function of the flavor number near the conformal window of many-flavor QCD in
the chiral limit. We argue on general grounds that the associated critical
exponents are all interrelated and can be determined from the critical exponent
of the running gauge coupling at the Caswell-Banks-Zaks infrared fixed point.
We illustrate our findings with the aid of nonperturbative functional
Renormalization Group (RG) calculations and low-energy QCD models.Comment: 18 pages, 4 figures, references added and discussion expanded
(matches JHEP version
Natural fourth generation of leptons
We consider implications of a fourth generation of leptons, allowing for the
most general mass patterns for the fourth generation neutrino. We determine the
constraints due to the precision electroweak measurements and outline the
signatures to search for at the LHC experiments. As a concrete framework to
apply these results we consider the minimal walking technicolor (MWTC) model
where the matter content, regarding the electroweak quantum numbers,
corresponds to a fourth generation.Comment: 21 pages, 11 figures, 1 table; version to appear in JHE
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