1,795 research outputs found
Metastable Vacua in Superconformal SQCD-like Theories
We study dynamical supersymmetry breaking in vector-like superconformal N=1
gauge theories. We find appropriate deformations of the superpotential to
overcome the problem of the instability of the non supersymmetric vacuum. The
request for long lifetime translates into constraints on the physical couplings
which in this regime can be controlled through efficient RG analysis.Comment: 17 pages, 7 figures, JHEP3.cl
Confinement-based direct design method for fibre reinforced polymer confined CFST short columns
The paper presents a detailed analysis of the behaviour of circular and square concrete filled steel tube (CFST) short columns strengthened externally with carbon or glass fibre reinforced polymer sheets (CFRP or GFRP, respectively). A thorough review of existing test information is presented and discussed, and the most salient parameters in terms of the overall strength are identified. There are a large number of influential and inter-related parameters which affect the load-carrying capacity, including the geometry, cross-sectional shape, type of steel, concrete strength, boundary and loading conditions, and type of FRP. It is shown that existing design approaches do not reliably predict the strength for the full range of possible parameters. Therefore, this paper proposes a new design model to calculate the axial compressive strength of FRP-confined concrete filled steel tubular (CFST) short columns with either a circular or square cross-section. The method accounts for the various complexities which affect the behaviour, yet presents a user-friendly, performance-based design expression. It is based on an evaluation of the lateral confining pressure provided by the both the FRP and the steel tube to the concrete core. This is employed in the confinement-based direct resistance calculations. The paper validates the approach by comparing its capacity predictions with a large database of experimental results and alternative design models available in the literature. The results show that the proposed model provides much accurate strength predictions with greater reliability for the full range of parameters examined, than existing methods
General Aspects of Tree Level Gauge Mediation
Tree level gauge mediation (TGM) may be considered as the simplest way to
communicate supersymmetry breaking: through the tree level renormalizable
exchange of heavy gauge messengers. We study its general structure, in
particular the general form of tree level sfermion masses and of one loop, but
enhanced, gaugino masses. This allows us to set up general guidelines for model
building and to identify the hypotheses underlying the phenomenological
predictions. In the context of models based on the "minimal" gauge group
SO(10), we show that only two "pure" embeddings of the MSSM fields are possible
using representations, each of them leading to specific predictions
for the ratios of family universal sfermion masses at the GUT scale,
or (in SU(5)
notation). These ratios are determined by group factors and are peculiar enough
to make this scheme testable at the LHC. We also discuss three possible
approaches to the -problem, one of them distinctive of TGM.Comment: 37 pages, 2 figure
Holographic metastability
We show how supersymmetric QCD in a slice of AdS can naturally acquire
metastable vacua. The formulation closely follows that of Intriligator, Seiberg
and Shih (ISS), with an "electric" sector on the UV brane and a "magnetic"
sector on the IR brane. However the 't Hooft anomaly matching that constrains
the Seiberg duality central to ISS is replaced by anomaly inflow and
cancellation, and the source of strong coupling is the CFT to which the theory
couples rather than the gauge groups. The theory contains an anomaly free
R-symmetry that, when broken by UV effects, leads to an O'Raifeartaigh model on
the IR brane. In contrast to ISS, the R-symmetry breaking in the UV can be
maximal, and yet the R-symmetry breaking in the IR theory remains under strict
control: there is no need for retrofitting of small parameters.Comment: 20 pages, 2 figure
Superconformal Flavor Simplified
A simple explanation of the flavor hierarchies can arise if matter fields
interact with a conformal sector and different generations have different
anomalous dimensions under the CFT. However, in the original study by Nelson
and Strassler many supersymmetric models of this type were considered to be
'incalculable' because the R-charges were not sufficiently constrained by the
superpotential. We point out that nearly all such models are calculable with
the use of a-maximization. Utilizing this, we construct the simplest
vector-like flavor models and discuss their viability. A significant constraint
on these models comes from requiring that the visible gauge couplings remain
perturbative throughout the conformal window needed to generate the
hierarchies. However, we find that there is a small class of simple flavor
models that can evade this bound.Comment: 43 pages, 1 figure; V3: small corrections and clarifications,
references adde
A microscopic theory of gauge mediation
We construct models of indirect gauge mediation where the dynamics
responsible for breaking supersymmetry simultaneously generates a weakly
coupled subsector of messengers. This provides a microscopic realization of
messenger gauge mediation where the messenger and hidden sector fields are
unified into a single sector. The UV theory is SQCD with massless and massive
quarks plus singlets, and at low energies it flows to a weakly coupled quiver
gauge theory. One node provides the primary source of supersymmetry breaking,
which is then transmitted to the node giving rise to the messenger fields.
These models break R-symmetry spontaneously, produce realistic gaugino and
sfermion masses, and give a heavy gravitino.Comment: 24 pages, 2 figures, accepted to JHEP for publicatio
SU(7) Unification of SU(3)_C*SU(4)_W* U(1)_{B-L}
We propose the SUSY SU(7) unification of the SU(3)_C* SU(4)_W* U(1)_{B-L}
model. Such unification scenario has rich symmetry breaking chains in a
five-dimensional orbifold. We study in detail the SUSY SU(7) symmetry breaking
into SU(3)_C* SU(4)_W* U(1)_{B-L} by boundary conditions in a Randall-Sundrum
background and its AdS/CFT interpretation. We find that successful gauge
coupling unification can be achieved in our scenario. Gauge unification favors
low left-right and unification scales with tree-level \sin^2\theta_W=0.15. We
use the AdS/CFT dual of the conformal supersymmetry breaking scenario to break
the remaining N=1 supersymmetry. We employ AdS/CFT to reproduce the NSVZ
formula and obtain the structure of the Seiberg duality in the strong coupling
region for 3/2N_c<N_F<3N_C. We show that supersymmetry is indeed broken in the
conformal supersymmetry breaking scenario with a vanishing singlet vacuum
expectation value.Comment: 25 pages, 1 figure
Notes on Operator Equations of Supercurrent Multiplets and the Anomaly Puzzle in Supersymmetric Field Theories
Recently, Komargodski and Seiberg have proposed a new type of supercurrent
multiplet which contains the energy-momentum tensor and the supersymmetry
current consistently. In this paper we study quantum properties of the
supercurrent in renormalizable field theories. We point out that the new
supercurrent gives a quite simple resolution to the classic problem, called the
anomaly puzzle, that the Adler-Bardeen theorem applied to an R-symmetry current
is inconsistent with all order corrections to functions. We propose an
operator equation for the supercurrent in all orders of perturbation theory,
and then perform several consistency checks of the equation. The operator
equation we propose is consisitent with the one proposed by Shifman and
Vainshtein, if we take some care in interpreting the meaning of non-conserved
currents.Comment: 28 pages; v2:clarifications and references added, some minor change
Soft Spectrum in Yukawa-Gauge Mediation
We introduce a model independent parametrization for a subclass of gauge
mediated theories, which we refer to as Yukawa-gauge mediation. Within this
formalism we study the resulting soft masses in the visible spectrum. We find
general expressions for the gaugino and scalar masses. Under generic
conditions, the gaugino mass is screened, vanishing at first order in the SUSY
breaking scale.Comment: 22 pages, 4 figures; v2: minor corrections, published versio
Aspects of Non-minimal Gauge Mediation
A large class of non-minimal gauge mediation models, such as (semi-)direct
gauge mediation, predict a hierarchy between the masses of the supersymmetric
standard model gauginos and those of scalar particles. We perform a
comprehensive study of these non-minimal gauge mediation models, including mass
calculations in semi-direct gauge mediation, to illustrate these features, and
discuss the phenomenology of the models. We point out that the cosmological
gravitino problem places stringent constraints on mass splittings, when the
Bino is the NLSP. However, the GUT relation of the gaugino masses is broken
unlike the case of minimal gauge mediation, and an NLSP other than the Bino
(especially the gluino NLSP) becomes possible, relaxing the cosmological
constraints. We also discuss the collider signals of the models.Comment: 56 pages, 8 figures; v2:minor corrections, references added; v3:minor
correction
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