216 research outputs found

### Calibrations, Monopoles and Fuzzy Funnels

We present new non-Abelian solitonic configurations in the low energy
effective theory describing a collection of N parallel D1--branes. These
configurations preserve 1/4, 1/8, 1/16 and 1/32 of the spacetime supersymmetry.
They are solutions to a set of generalised Nahm's equations which are related
to self-duality equations in eight dimensions. Our solutions represent
D1--branes which expand into fuzzy funnel configurations ending on collections
of intersecting D3--branes. Supersymmetry dictates that such intersecting
D3--branes must lie on a calibrated three-surface of spacetime and we argue
that the generalised Nahm's equations encode the data for the construction of
magnetic monopoles on the relevant three-surfaces.Comment: 19 pages. Latex. v2: added references and acknowledgmen

### Non-Abelian Field Theory of stable non-BPS Branes

We derive the action for the non-abelian field theory living on parallel
non-BPS D3-branes in type IIA theory on the orbifold T^4/I_4(-1)^F_L. The
classical moduli space for the massless scalars originating in the ``would be''
tachyonic sector shows an interesting structure. In particular, it contains
non-abelian flat directions. At a generic point in this branch of the moduli
space the scalars corresponding to the the separations of the branes acquire
masses and the branes condense. Although these tree level flat directions are
removed by quantum corrections we argue that within the loop approximation the
branes still condense.Comment: 1 reference adde

### Dyonic Instantons in Five Dimensional Gauge Theories

We show that there exist finite energy, non-singular instanton solutions for
five-dimensional theories with broken gauge symmetry. The soliton is supported
against collapse by a non-zero electric charge. The low-energy dynamics of
these solutions is described by motion on the ADHM moduli space with potential.Comment: 9 pages. Latex. Minor typos, including correction to final equatio

### Branes and Calibrated Geometries

The fivebrane worldvolume theory in eleven dimensions is known to contain BPS
threebrane solitons which can also be interpreted as a fivebrane whose
worldvolume is wrapped around a Riemann surface. By considering configurations
of intersecting fivebranes and hence intersecting threebrane solitons, we
determine the Bogomol'nyi equations for more general BPS configurations. We
obtain differential equations, generalising Cauchy-Riemann equations, which
imply that the worldvolume of the fivebrane is wrapped around a calibrated
geometry.Comment: Latex, 35 pages. References added, minor change

### Cost effectiveness analysis of different approaches of screening for familial hypercholesterolaemia

Objectives To assess the cost effectiveness of
strategies to screen for and treat familial
hypercholesterolaemia.
Design Cost effectiveness analysis. A care pathway for
each patient was delineated and the associated
probabilities, benefits, and costs were calculated.
Participants Simulated population aged 16Â54 years
in England and Wales.
Interventions Identification and treatment of patients
with familial hypercholesterolaemia by universal
screening, opportunistic screening in primary care,
screening of people admitted to hospital with
premature myocardial infarction, or tracing family
members of affected patients.
Main outcome measure Cost effectiveness calculated
as cost per life year gained (extension of life
expectancy resulting from intervention) including
estimated costs of screening and treatment.
Results Tracing of family members was the most cost
effective strategy (ÂŁ3097 (&5066, $4479) per life year
gained) as 2.6 individuals need to be screened to
identify one case at a cost of ÂŁ133 per case detected. If
the genetic mutation was known within the family
then the cost per life year gained (ÂŁ4914) was only
slightly increased by genetic confirmation of the
diagnosis. Universal population screening was least
cost effective (ÂŁ13 029 per life year gained) as 1365
individuals need to be screened at a cost of ÂŁ9754 per
case detected. For each strategy it was more cost
effective to screen younger people and women.
Targeted strategies were more expensive per person
screened, but the cost per case detected was lower.
Population screening of 16 year olds only was as cost
effective as family tracing (ÂŁ2777 with a clinical
confirmation).
Conclusions Screening family members of people
with familial hypercholesterolaemia is the most cost
effective option for detecting cases across the whole
population

### A Calibration Bound for the M-Theory Fivebrane

We construct a covariant bound on the energy-momentum of the M-fivebrane
which is saturated by all supersymmetric configurations. This leads to a
generalised notion of a calibrated geometry for M-fivebranes when the
worldvolume gauge field is non-zero. The generalisation relevant for Dp-branes
is also given.Comment: 9 pages, LaTeX2e, uses vmargin.sty. Typos corrected, a reference and
a new discussion on conserved charges added. v4: A typo in the expression for
the D-fourbrane energy correcte

### On the Energy Momentum Tensor of the M-Theory Fivebrane

We construct the energy momentum tensor for the bosonic fields of the
covariant formulation of the M-theory fivebrane within that formalism. We then
obtain the energy for various solitonic solutions of the fivebrane equations of
motion.Comment: 12 pages, LaTeX2e, uses vmargin.sty and amstex.st

### Relating U(N)xU(N) to SU(N)xSU(N) Chern-Simons Membrane theories

By integrating out the U(1)_B gauge field, we show that the U(n)xU(n) ABJM
theory at level k is equivalent to a Z_k identification of the
(SU(n)xSU(n))/Z_n Chern-Simons theory, but only when n and k are coprime. As a
consequence, the k=1 ABJM model for two M2-branes in R^8 can be identified with
the N=8 (SU(2)xSU(2))/Z_2 theory. We also conjecture that the U(2)xU(2) ABJM
model at k=2 is equivalent to the N=8 SU(2)xSU(2)-theory.Comment: 16 pages, Latex; v2: references added; v3: Clarifications adde

### Kinky D-Strings

We study two-dimensional SQED viewed as the world-volume theory of a D-string
in the presence of D5-branes with non-zero background fields that induce
attractive forces between the branes. In various approximations, the low-energy
dynamics is given by a hyperKahler, or hyperKahler with torsion, massive
sigma-model. We demonstrate the existence of kink solutions corresponding to
the string interpolating between different D5-branes. Bound states of the
D-string with fundamental strings are identified with Q-kinks which, in turn,
are identified with dyonic instanton strings on the D5-brane world-volume.Comment: Latex. 23 pages. 1 figur

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