99 research outputs found
Sleep problems are associated with chronic pain over and above mutual associations with depression and catastrophizing
INTRODUCTION
Pain, mood problems and sleeping difficulties are often comorbid and contribute to reduced physical function and quality of life for those suffering from chronic pain. However, the way in which these factors interact is unclear. Until recently it was thought that the effect of sleep on pain and physical function was simply a result of its common association with mood problems. However, a growing body of research suggests that sleep may have a unique contribution.
OBJECTIVES
The aim of this study was to determine whether sleep disturbances were associated with pain and poor physical function independent of psychological distress in patients attending a tertiary pain medicine unit.
METHOD
101 patients with chronic pain completed a set of questionnaires measuring pain, sleep and mood, and also completed a selection of physical assessments conducted by a physiotherapist.
RESULTS
75.2% of participants had insomnia and 84.3% reported the presence of at least one sleep problem. Significant positive correlations with pain were detected for depression, catastrophizing, insomnia, short sleep duration and poor sleep quality. Sleep duration had a significant independent association with pain after accounting for depression and catastrophizing. Sleep duration also had an independent association with physical function after accounting for pain and catastrophizing.
CONCLUSIONS
Given that sleep has an important and unique contribution to pain and physical function, it is important that sleep disturbances are addressed both in the assessment and treatment of chronic pain
N=8 Supergravity 4-point Amplitudes
We present the explicit expressions in N=8 supergravity for the bosonic
4-particle tree and 1-loop amplitudes including vectors and scalars. We also
present the candidate 4-point UV divergences in a form of helicity amplitudes,
corresponding to 3-loop manifestly N=8 supersymmetric and Lorentz covariant
counterterm. This may shed some light on the 3-loop finiteness of N=8 SG and on
a conjectured higher loop finiteness. We perform a supersymmetric deformation
to complex momentum of the 4-point generating function including higher-loop
counterterms and the 1-loop UV finite amplitudes. Using the explicit form of
the scalar part of the 3-loop counterterm and of the 1-loop UV finite scalar
4-point amplitudes we find that they both have an unbroken E7 symmetry. We
derive from E7 symmetry the low-energy theorem for the 1-loop n-point
amplitudes.Comment: 23 p, 4 figure
Proof of the MHV vertex expansion for all tree amplitudes in N=4 SYM theory
We prove the MHV vertex expansion for all tree amplitudes of N=4 SYM theory.
The proof uses a shift acting on all external momenta, and we show that every
N^kMHV tree amplitude falls off as 1/z^k, or faster, for large z under this
shift. The MHV vertex expansion allows us to derive compact and efficient
generating functions for all N^kMHV tree amplitudes of the theory. We also
derive an improved form of the anti-NMHV generating function. The proof leads
to a curious set of sum rules for the diagrams of the MHV vertex expansion.Comment: 40 pages, 7 figure
Non-renormalization conditions for four-gluon scattering in supersymmetric string and field theory
The constraints imposed by maximal supersymmetry on multi-loop contributions
to the scattering of four open superstrings in the U(N) theory are examined by
use of the pure spinor formalism. The double-trace term k^2 t_8(tr F^2)^2
(where k represents an external momentum and F the Yang--Mills field strength)
only receives contributions from L<=2 (where L is the loop number) while the
single-trace term k^2 t_8(tr F^4) receives contributions from all L. We
verified these statements up to L=5, but arguments based on supersymmetry
suggest they extend to all L. This explains why the single-trace contributions
to low energy maximally supersymmetric Yang--Mills field theory are more
divergent in the ultraviolet than the double-trace contributions. We also
comment further on the constraints on closed string amplitudes and their
implications for ultraviolet divergences in N=8 supergravity.Comment: 25 pages. 2 eps figures. Harvmac format. v2 qualifications regarding
comments on closed strings. References adde
The non-abelian D-brane effective action through order
Requiring the existence of certain BPS solutions to the equations of motion,
we determine the bosonic part of the non-abelian D-brane effective action
through order . We also propose an economic organizational
principle for the effective action.Comment: 12 pages, 2 figures, JHEP styl
Further results for the two-loop Lcc vertex in the Landau gauge
In the previous paper hep-th/0604112 we calculated the first of the five
planar two-loop diagrams for the Lcc vertex of the general non-Abelian
Yang-Mills theory, the vertex which allows us in principle to obtain all other
vertices via the Slavnov-Taylor identity. The integrand of this first diagram
has a simple Lorentz structure. In this letter we present the result for the
second diagram, whose integrand has a complicated Lorentz structure. The
calculation is performed in the D-dimensional Euclidean position space. We
initially perform one of the two integrations in the position space and then
reduce the Lorentz structure to D-dimensional scalar single integrals. Some of
the latter are then calculated by the uniqueness method, others by the
Gegenbauer polynomial technique. The result is independent of the ultraviolet
and the infrared scale. It is expressed in terms of the squares of spacetime
intervals between points of the effective fields in the position space -- it
includes simple powers of these intervals, as well as logarithms and
polylogarithms thereof, with some of the latter appearing within the Davydychev
integral J(1,1,1). Concerning the rest of diagrams, we present the result for
the contributions correponding to third, fourth and fifth diagrams without
giving the details of calculation. The full result for the Lcc correlator of
the effective action at the planar two-loop level is written explicitly for
maximally supersymmetric Yang-Mills theory.Comment: 29 pages, 1 figure, minor changes; three references added, one new
paragraph in Introduction added, Note Added is extended; to appear in JHE
On the effective action of confining strings
We study the low-energy effective action on confining strings (in the
fundamental representation) in SU(N) gauge theories in D space-time dimensions.
We write this action in terms of the physical transverse fluctuations of the
string. We show that for any D, the four-derivative terms in the effective
action must exactly match the ones in the Nambu-Goto action, generalizing a
result of Luscher and Weisz for D=3. We then analyze the six-derivative terms,
and we show that some of these terms are constrained. For D=3 this uniquely
determines the effective action for closed strings to this order, while for D>3
one term is not uniquely determined by our considerations. This implies that
for D=3 the energy levels of a closed string of length L agree with the
Nambu-Goto result at least up to order 1/L^5. For any D we find that the
partition function of a long string on a torus is unaffected by the free
coefficient, so it is always equal to the Nambu-Goto partition function up to
six-derivative order. For a closed string of length L, this means that for D>3
its energy can, in principle, deviate from the Nambu-Goto result at order
1/L^5, but such deviations must always cancel in the computation of the
partition function. Next, we compute the effective action up to six-derivative
order for the special case of confining strings in weakly-curved holographic
backgrounds, at one-loop order (leading order in the curvature). Our
computation is general, and applies in particular to backgrounds like the
Witten background, the Maldacena-Nunez background, and the Klebanov-Strassler
background. We show that this effective action obeys all of the constraints we
derive, and in fact it precisely agrees with the Nambu-Goto action (the single
allowed deviation does not appear).Comment: 71 pages, 7 figures. v2: added reference, minor corrections. v3:
removed one term from the effective action since it is trivial. The
conclusions on the corrections to energy levels are unchanged, but the claim
that the holographic computation shows a deviation from Nambu-Goto was
modified. v4: added reference
4-point effective actions in open and closed superstring theory
Recently the effective action for the 4-point functions in abelian open
superstring theory has been derived, giving an explicit construction of the
bosonic and fermionic terms of this infinite series. In the present
work we generalize this result to the nonabelian case. We test our result, at
and order, with several existing versions for these
terms, finding agreement in most of the cases. We also apply these ideas to
derive the effective action for the 4-point functions of the NS-NS sector of
closed superstring theory, to all order in .Comment: 26 pages, 1 figure. To appear in JHE
On the effective string spectrum of the tridimensional Z(2) gauge model
We study the Z(2) lattice gauge theory in three dimensions, and present high
precision estimates for the first few energy levels of the string spectrum.
These results are obtained from new numerical data for the two-point Polyakov
loop correlation function, which is measured in the 3d Ising spin system using
duality. This allows us to perform a stringent comparison with the predictions
of effective string models. We find a remarkable agreement between the
numerical estimates and the Nambu-Goto predictions for the energy gaps at
intermediate and large distances. The precision of our data allows to
distinguish clearly between the predictions of the full Nambu-Goto action and
the simple free string model up to an interquark distance . At the same time, our results also confirm the breakdown of
the effective picture at short distances, supporting the hypothesis that terms
which are not taken into account in the usual Nambu-Goto string formulation
yield a non-trivial shift to the energy levels. Furthermore, we discuss the
theoretical implications of these results.Comment: 31 pages, 14 figure
A super MHV vertex expansion for N=4 SYM theory
We present a supersymmetric generalization of the MHV vertex expansion for
all tree amplitudes in N=4 SYM theory. In addition to the choice of a reference
spinor, this super MHV vertex expansion also depends on four reference
Grassmann parameters. We demonstrate that a significant fraction of diagrams in
the expansion vanishes for a judicious choice of these Grassmann parameters,
which simplifies the computation of amplitudes. Even pure-gluon amplitudes
require fewer diagrams than in the ordinary MHV vertex expansion.
We show that the super MHV vertex expansion arises from the recursion
relation associated with a holomorphic all-line supershift. This is a
supersymmetric generalization of the holomorphic all-line shift recently
introduced in arXiv:0811.3624. We study the large-z behavior of generating
functions under these all-line supershifts, and find that they generically
provide 1/z^k falloff at (Next-to)^k MHV level. In the case of anti-MHV
generating functions, we find that a careful choice of shift parameters
guarantees a stronger 1/z^(k+4) falloff. These particular all-line supershifts
may therefore play an important role in extending the super MHV vertex
expansion to N=8 supergravity.Comment: 26 pages, 3 figures, v2: analytic expression for counting of super
MHV vertex diagrams added; references adde
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