3,966 research outputs found
Asymptotically Safe Dark Matter
We introduce a new paradigm for dark matter (DM) interactions in which the
interaction strength is asymptotically safe. In models of this type, the
coupling strength is small at low energies but increases at higher energies,
and asymptotically approaches a finite constant value. The resulting
phenomenology of this "asymptotically safe DM" is quite distinct. One
interesting effect of this is to partially offset the low-energy constraints
from direct detection experiments without affecting thermal freeze-out
processes which occur at higher energies. High-energy collider and indirect
annihilation searches are the primary ways to constrain or discover
asymptotically safe dark matter.Comment: 5 pages, 2 multi-panel figures, PRD versio
Corrigan-Ramond Extension of QCD at Nonzero Baryon Density
We investigate the Corrigan-Ramond extension of one massless flavor Quantum
Chromo Dynamics at nonzero quark chemical potential. Since the extension
requires the fermions to transform in the two index antisymmetric
representation of the gauge group, one finds that the number of possible
channels is richer than in the 't Hooft limit. We first discuss the diquark
channels and show that for a number of colors larger than three a new diquark
channel appears. We then study the infinite number of color limit and show that
the Fermi surface is unstable to the formation of the
Deryagin-Grigoriev-Rubakov chiral waves. We discover, differently from the 't
Hooft limit, the possibility of a colored chiral wave breaking the color
symmetry as well as translation invariance.Comment: RevTeX, 14 pages, 2 figure
Weinberg-Salam model at finite temperature and density
We present a new gauge fixing condition for the Weinberg-Salam electro-weak
theory at finite temperature and density.
After spontaneous symmetry breaking occurs, every unphysical term in the
Lagrangian is eliminated with our gauge fixing condition. A new and simple
Lagrangian can be obtained where we can identify the propagators and vertices.
Some consequences are discussed, as the new gauge dependent masses of the gauge
fields and the new Faddeev-Popov Lagrangian. After obtaining the quadratic
terms, we calculate exactly the 1-loop effective potential identifying the
contribution of every particular field.Comment: 4 pages, no figures. New references added. Typo correcte
Scaling Behavior in Soliton Models
In the framework of chiral soliton models we study the behavior of static
nucleon properties under rescaling of the parameters describing the effective
meson theory. In particular we investigate the question of whether the
Brown--Rho scaling laws are general features of such models. When going beyond
the simple Skyrme model we find that restrictive constraints need to be imposed
on the mesonic parameters in order to maintain these scaling laws. Furthermore,
in the case when vector mesons are included in the model it turns out that the
isoscalar form factor no longer scales according to these laws. Finally we note
that, in addition to the exact scaling laws of the model, one may construct
approximate {\it local scaling laws}, which depend of the particular choice of
Lagrangian parameters.Comment: 10 pages Latex, figures added using epsfi
Minimal Super Technicolor
We introduce novel extensions of the Standard Model featuring a
supersymmetric technicolor sector. First we consider N=4 Super Yang-Mills which
breaks to N=1 via the electroweak (EW) interactions and coupling to the MSSM.
This is a well defined, economical and calculable extension of the SM involving
the smallest number of fields. It constitutes an explicit example of a natural
supersymmetric conformal extension of the Standard Model featuring a well
defined connection to string theory. It allows to interpolate, depending on how
we break the underlying supersymmetry, between unparticle physics and Minimal
Walking Technicolor. As a second alternative we consider other N =1 extensions
of the Minimal Walking Technicolor model. The new models allow all the standard
model matter fields to acquire a mass.Comment: Improved version demonstrating that this extension is
phenomenologically viable. No Landau pole exists in the theory to two loops
level. This is the first theory showing that supersymmetry can solve the
flavor problem when coupled to low energy technicolo
X-ray Lines from Dark Matter: The Good, The Bad, and The Unlikely
We consider three classes of dark matter (DM) models to account for the
recently observed 3.5 keV line: metastable excited state DM, annihilating DM,
and decaying DM. We study two examples of metastable excited state DM. The
first, millicharged composite DM, has both inelasticity and photon emission
built in, but with a very constrained parameter space. In the second example,
up-scattering and decay come from separate sectors and is thus less
constrained. The decay of the excited state can potentially be detectable at
direct detection experiments. However we find that CMB constraints are at the
border of excluding this as an interpretation of the DAMA signal. The
annihilating DM interpretation of the X-ray line is found to be in tension with
CMB constraints. Lastly, a generalized version of decaying DM can account for
the data with a lifetime exceeding the age of the Universe for masses GeV.Comment: 14 pages, 4 figures; updated to match JCAP published versio
Conformal Windows of SU(N) Gauge Theories, Higher Dimensional Representations and The Size of The Unparticle World
We present the conformal windows of SU(N) supersymmetric and
nonsupersymmetric gauge theories with vector-like matter transforming according
to higher irreducible representations of the gauge group. We determine the
fraction of asymptotically free theories expected to develop an infrared fixed
point and find that it does not depend on the specific choice of the
representation. This result is exact in supersymmetric theories while it is an
approximate one in the nonsupersymmetric case. The analysis allows us to size
the unparticle world related to the existence of underlying gauge theories
developing an infrared stable fixed point. We find that exactly 50 % of the
asymptotically free theories can develop an infrared fixed point while for the
nonsupersymmetric theories it is circa 25 %. When considering multiple
representations, only for the nonsupersymmetric case, the conformal regions
quickly dominate over the nonconformal ones. For four representations, 70 % of
the asymptotically free space is filled by the conformal region.
According to our theoretical landscape survey the unparticle physics world
occupies a sizable amount of the particle world, at least in theory space, and
before mixing it (at the operator level) with the nonconformal one.Comment: RevTeX, 18 pages, 2 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
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
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
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