5,912 research outputs found
Piezoelectric-based apparatus for strain tuning
We report the design and construction of piezoelectric-based apparatus for
applying continuously tuneable compressive and tensile strains to test samples.
It can be used across a wide temperature range, including cryogenic
temperatures. The achievable strain is large, so far up to 0.23% at cryogenic
temperatures. The apparatus is compact and compatible with a wide variety of
experimental probes. In addition, we present a method for mounting
high-aspect-ratio samples in order to achieve high strain homogeneity.Comment: 8 pages, 8 figure
On gravitational-wave spectroscopy of massive black holes with the space interferometer LISA
Newly formed black holes are expected to emit characteristic radiation in the
form of quasi-normal modes, called ringdown waves, with discrete frequencies.
LISA should be able to detect the ringdown waves emitted by oscillating
supermassive black holes throughout the observable Universe. We develop a
multi-mode formalism, applicable to any interferometric detectors, for
detecting ringdown signals, for estimating black hole parameters from those
signals, and for testing the no-hair theorem of general relativity. Focusing on
LISA, we use current models of its sensitivity to compute the expected
signal-to-noise ratio for ringdown events, the relative parameter estimation
accuracy, and the resolvability of different modes. We also discuss the extent
to which uncertainties on physical parameters, such as the black hole spin and
the energy emitted in each mode, will affect our ability to do black hole
spectroscopy.Comment: 44 pages, 21 figures, 10 tables. Minor changes to match version in
press in Phys. Rev.
Post-Newtonian gravitational radiation and equations of motion via direct integration of the relaxed Einstein equations. III. Radiation reaction for binary systems with spinning bodies
Using post-Newtonian equations of motion for fluid bodies that include
radiation-reaction terms at 2.5 and 3.5 post-Newtonian (PN) order (O[(v/c)^5]
and O[(v/c)^7] beyond Newtonian order), we derive the equations of motion for
binary systems with spinning bodies. In particular we determine the effects of
radiation-reaction coupled to spin-orbit effects on the two-body equations of
motion, and on the evolution of the spins. For a suitable definition of spin,
we reproduce the standard equations of motion and spin-precession at the first
post-Newtonian order. At 3.5PN order, we determine the spin-orbit induced
reaction effects on the orbital motion, but we find that radiation damping has
no effect on either the magnitude or the direction of the spins. Using the
equations of motion, we find that the loss of total energy and total angular
momentum induced by spin-orbit effects precisely balances the radiative flux of
those quantities calculated by Kidder et al. The equations of motion may be
useful for evolving inspiraling orbits of compact spinning binaries.Comment: 19 pages, small corrections, equivalent to published versio
Covers of acts over monoids II
In 1981 Edgar Enochs conjectured that every module has a flat cover and
finally proved this in 2001. Since then a great deal of effort has been spent
on studying different types of covers, for example injective and torsion free
covers. In 2008, Mahmoudi and Renshaw initiated the study of flat covers of
acts over monoids but their definition of cover was slightly different from
that of Enochs. Recently, Bailey and Renshaw produced some preliminary results
on the `other' type of cover and it is this work that is extended in this
paper. We consider free, divisible, torsion free and injective covers and
demonstrate that in some cases the results are quite different from the module
case
Amplitudes and Spinor-Helicity in Six Dimensions
The spinor-helicity formalism has become an invaluable tool for understanding
the S-matrix of massless particles in four dimensions. In this paper we
construct a spinor-helicity formalism in six dimensions, and apply it to derive
compact expressions for the three, four and five point tree amplitudes of
Yang-Mills theory. Using the KLT relations, it is a straightforward process to
obtain amplitudes in linearized gravity from these Yang-Mills amplitudes; we
demonstrate this by writing down the gravitational three and four point
amplitudes. Because there is no conserved helicity in six dimensions, these
amplitudes describe the scattering of all possible polarization states (as well
as Kaluza-Klein excitations) in four dimensions upon dimensional reduction. We
also briefly discuss a convenient formulation of the BCFW recursion relations
in higher dimensions.Comment: 26 pages, 2 figures. Minor improvements of the discussio
Higgs Mass from D-Terms: a Litmus Test
We explore supersymmetric theories in which the Higgs mass is boosted by the
non-decoupling D-terms of an extended gauge symmetry, defined here to
be a general linear combination of hypercharge, baryon number, and lepton
number. Crucially, the gauge coupling, , is bounded from below to
accommodate the Higgs mass, while the quarks and leptons are required by gauge
invariance to carry non-zero charge under . This induces an irreducible
rate, BR, for relevant to
existing and future resonance searches, and gives rise to higher dimension
operators that are stringently constrained by precision electroweak
measurements. Combined, these bounds define a maximally allowed region in the
space of observables, (BR, ), outside of which is excluded by
naturalness and experimental limits. If natural supersymmetry utilizes
non-decoupling D-terms, then the associated boson can only be observed
within this window, providing a model independent `litmus test' for this broad
class of scenarios at the LHC. Comparing limits, we find that current LHC
results only exclude regions in parameter space which were already disfavored
by precision electroweak data.Comment: 7 pages, 9 figure
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