2,703 research outputs found
E7(7) invariant Lagrangian of d=4 N=8 supergravity
We present an E7(7) invariant Lagrangian that leads to the equations of
motion of d=4 N=8 supergravity without using Lagrange multipliers. The
superinvariance of this new action and the closure of the supersymmetry algebra
are proved explicitly for the terms that differ from the Cremmer--Julia
formulation. Since the diffeomorphism symmetry is not realized in the standard
way on the vector fields, we switch to the Hamiltonian formulation in order to
prove the invariance of the E7(7) invariant action under general coordinate
transformations. We also construct the conserved E7(7)-Noether current of
maximal supergravity and we conclude with comments on the implications of this
manifest off-shell E7(7)-symmetry for quantizing d=4 N=8 supergravity, in
particular on the E7(7)-action on phase space.Comment: 45 pages, references adde
Efficacy of an ankle orthosis with a subtalar locking system in restricting ankle kinetics and kinematics in lateral cutting
Introduction
The ankle joint is the most injured joint during sports participation [1]. Ankle orthoses have been shown to be effective in reducing ankle inversion injuries and are often prescribed for rehabilitation and prevention of lateral ankle sprains. Efficacy of ankle orthoses is often assessed by comparing reduction of passive inversion ROM as well as ankle kinematics between braced and unbraced movements [2,3]. However, joint kinetic responses in lateral cutting were rarely examined. Therefore, the objective of this study was to examine the effectiveness of a new semi-rigid ankle orthosis with a subtalar joint locking mechanism in restricting ankle kinetics and kinematics during a lateral cutting movement
Non-Abelian statistics and topological quantum information processing in 1D wire networks
Topological quantum computation provides an elegant way around decoherence,
as one encodes quantum information in a non-local fashion that the environment
finds difficult to corrupt. Here we establish that one of the key
operations---braiding of non-Abelian anyons---can be implemented in
one-dimensional semiconductor wire networks. Previous work [Lutchyn et al.,
arXiv:1002.4033 and Oreg et al., arXiv:1003.1145] provided a recipe for driving
semiconducting wires into a topological phase supporting long-sought particles
known as Majorana fermions that can store topologically protected quantum
information. Majorana fermions in this setting can be transported, created, and
fused by applying locally tunable gates to the wire. More importantly, we show
that networks of such wires allow braiding of Majorana fermions and that they
exhibit non-Abelian statistics like vortices in a p+ip superconductor. We
propose experimental setups that enable the Majorana fusion rules to be probed,
along with networks that allow for efficient exchange of arbitrary numbers of
Majorana fermions. This work paves a new path forward in topological quantum
computation that benefits from physical transparency and experimental realism.Comment: 6 pages + 17 pages of Supp. Mat.; 10 figures. Supp. Mat. has doubled
in size to establish results more rigorously; many other improvements as wel
Solution to the Ward Identities for Superamplitudes
Supersymmetry and R-symmetry Ward identities relate on-shell amplitudes in a
supersymmetric field theory. We solve these Ward identities for (Next-to)^K MHV
amplitudes of the maximally supersymmetric N=4 and N=8 theories. The resulting
superamplitude is written in a new, manifestly supersymmetric and R-invariant
form: it is expressed as a sum of very simple SUSY and SU(N)_R-invariant
Grassmann polynomials, each multiplied by a "basis amplitude". For (Next-to)^K
MHV n-point superamplitudes the number of basis amplitudes is equal to the
dimension of the irreducible representation of SU(n-4) corresponding to the
rectangular Young diagram with N columns and K rows. The linearly independent
amplitudes in this algebraic basis may still be functionally related by
permutation of momenta. We show how cyclic and reflection symmetries can be
used to obtain a smaller functional basis of color-ordered single-trace
amplitudes in N=4 gauge theory. We also analyze the more significant reduction
that occurs in N=8 supergravity because gravity amplitudes are not ordered. All
results are valid at both tree and loop level.Comment: 29 pages, published versio
An investigation of minimisation criteria
Minimisation can be used within treatment trials to ensure that prognostic factors are evenly distributed between treatment groups. The technique is relatively straightforward to apply but does require running tallies of patient recruitments to be made and some simple calculations to be performed prior to each allocation. As computing facilities have become more widely available, minimisation has become a more feasible option for many. Although the technique has increased in popularity, the mode of application is often poorly reported and the choice of input parameters not justified in any logical way
Dual conformal symmetry of 1-loop NMHV amplitudes in N=4 SYM theory
We prove that 1-loop n-point NMHV superamplitudes in N=4 SYM theory are dual
conformal covariant for all numbers n of external particles (after
regularization and subtraction of IR divergences). This property was previously
established for n < 10 in arXiv:0808.0491. We derive an explicit representation
of these superamplitudes in terms of dual conformal cross-ratios. We also show
that all the 1-loop `box coefficients' obtained from maximal cuts of N^kMHV
n-point functions are covariant under dual conformal transformations.Comment: 20 pages, 2 figure
Writing CFT correlation functions as AdS scattering amplitudes
We explore the Mellin representation of conformal correlation functions
recently proposed by Mack. Examples in the AdS/CFT context reinforce the
analogy between Mellin amplitudes and scattering amplitudes. We conjecture a
simple formula relating the bulk scattering amplitudes to the asymptotic
behavior of Mellin amplitudes and show that previous results on the flat space
limit of AdS follow from our new formula. We find that the Mellin amplitudes
are particularly useful in the case of conformal gauge theories in the planar
limit. In this case, the four point Mellin amplitudes are meromorphic functions
whose poles and their residues are entirely determined by two and three point
functions of single-trace operators. This makes the Mellin amplitudes the ideal
objects to attempt the conformal bootstrap program in higher dimensions.Comment: 23 pages + appendice
Hairy planar black holes in higher dimensions
We construct exact hairy planar black holes in D-dimensional AdS gravity.
These solutions are regular except at the singularity and have stress-energy
that satisfies the null energy condition. We present a detailed analysis of
their thermodynamical properties and show that the first law is satisfied. We
also discuss these solutions in the context of AdS/CFT duality and construct
the associated c-function.Comment: 18 pages, no figures; v2: title changed, typos fixe
The Non-SUSY Baryonic Branch: Soft Supersymmetry Breaking of N=1 Gauge Theories
We study a non-supersymmetric deformation of the field theory dual to the
baryonic branch of Klebanov-Strassler. Using a combination of analytical
(series expansions) and numerical methods we construct non-supersymmetric
backgrounds that smoothly interpolate between the desired UV and IR behaviors.
We calculate various observables of the field theory and propose a picture of
soft breaking by gaugino masses that is consistent with the various
calculations on the string side.Comment: 32 pages plus many appendixes. One figur
Scalar Three-point Functions in a CDL Background
Motivated by the FRW-CFT proposal by Freivogel, Sekino, Susskind and Yeh, we
compute the three-point function of a scalar field in a Coleman-De Luccia
instanton background. We first compute the three-point function of the scalar
field making only very mild assumptions about the scalar potential and the
instanton background. We obtain the three-point function for points in the FRW
patch of the CDL instanton and take two interesting limits; the limit where the
three points are near the boundary of the hyperbolic slices of the FRW patch,
and the limit where the three points lie on the past lightcone of the FRW
patch. We expand the past lightcone three-point function in spherical
harmonics. We show that the near boundary limit expansion of the three-point
function of a massless scalar field exhibits conformal structure compatible
with FRW-CFT when the FRW patch is flat. We also compute the three-point
function when the scalar is massive, and explain the obstacles to generalizing
the conjectured field-operator correspondence of massless fields to massive
fields.Comment: 42 pages + appendices, 10 figures; v2, v3: minor correction
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