358 research outputs found
Non-local Higgs actions: Tree-level electroweak constraints and high-energy unitarity
We consider electroweak symmetry breaking by a certain class of non-local
Higgs sectors. Extending previous studies employing the Mandelstam condition, a
straight Wilson line is used to make the Higgs action gauge invariant. We show
the unitarization of vector-boson scattering for a wide class of non-local
actions, but find that the Wilson-line model leads to tree-level corrections to
electroweak precision observables, which restrict the parameter space of the
model. We also find that Unhiggs models cannot address the hierarchy problem,
once the parameters are expressed in terms of low-energy observables.Comment: 22 pages, 6 Figure
Massive Spinors and dS/CFT Correspondence
Using the map between free massless spinors on d+1 dimensional Minkowski
spacetime and free massive spinors on , we obtain the boundary term
that should be added to the standard Dirac action for spinors in the dS/CFT
correspondence. It is shown that this map can be extended only to theories with
vertex ({\bar\p}\p)^2 but arbitrary . In the case of scalar field
theories such an extension can be made only for with vertices
, and respectively
Regular and Irregular Boundary Conditions in the AdS/CFT Correspondence
We expand on Klebanov and Witten's recent proposal for formulating the
AdS/CFT correspondence using irregular boundary conditions. The proposal is
shown to be correct to any order in perturbation theory.Comment: 7 pages, typos correcte
Magnetism in SQUIDs at Millikelvin Temperatures
We have characterized the temperature dependence of the flux threading dc
SQUIDs cooled to millikelvin temperatures. The flux increases as 1/T as
temperature is lowered; moreover, the flux change is proportional to the
density of trapped vortices. The data is compatible with the thermal
polarization of surface spins in the trapped fields of the vortices. In the
absence of trapped flux, we observe evidence of spin-glass freezing at low
temperature. These results suggest an explanation for the "universal" 1/f flux
noise in SQUIDs and superconducting qubits.Comment: 4 pages, 4 figure
Spectral Functions in Holographic Renormalization Group Flows
The spectrum of two-point functions in a holographic renormalization group
flow from an ultraviolet (UV) to an infrared (IR) conformal fixed point is
necessarily continuous. For a toy model, the spectral function does not only
show the expected UV and IR behaviours, but other interesting features such as
sharp peaks and oscillations in the UV. The spectral functions for the
SU(3)xU(1) flow in AdS_4/CFT_3 and the SU(2)xU(1) flow in AdS_5/CFT_4 are
calculated numerically. They exhibit a simple cross-over behaviour and
reproduce the conformal dimensions of the dual operators in the UV and IR
conformal phases.Comment: 20 pages, 6 figures v2: added referene
The massless gravitino and the AdS/CFT correspondence
We solve the Dirichlet boundary value problem for the massless gravitino on
space and compute the two-point function of the dual CFT
supersymmetry currents using the /CFT correspondence principle. We find
analogously to the spinor case that the boundary data for the massless
dimensional bulk gravitino field consists of only a dimensional
gravitino.Comment: 10 pages, RevTe
Spinor Parallel Propagator and Green's Function in Maximally Symmetric Spaces
We introduce the spinor parallel propagator for maximally symmetric spaces in
any dimension. Then, the Dirac spinor Green's functions in the maximally
symmetric spaces R^n, S^n and H^n are calculated in terms of intrinsic
geometric objects. The results are covariant and coordinate-independent.Comment: 7 page
Design and performance of the ADMX SQUID-based microwave receiver
The Axion Dark Matter eXperiment (ADMX) was designed to detect ultra-weakly
interacting relic axion particles by searching for their conversion to
microwave photons in a resonant cavity positioned in a strong magnetic field.
Given the extremely low expected axion-photon conversion power we have
designed, built and operated a microwave receiver based on a Superconducting
QUantum Interference Device (SQUID). We describe the ADMX receiver in detail as
well as the analysis of narrow band microwave signals. We demonstrate the
sustained use of a SQUID amplifier operating between 812 and 860 MHz with a
noise temperature of 1 K. The receiver has a noise equivalent power of
1.1x10^-24 W/sqrt(Hz) in the band of operation for an integration time of
1.8x10^3 s.Comment: 8 pages, 12 figures, Submitted to Nuclear Inst. and Methods in
Physics Research,
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