425 research outputs found
Instantons and Matter in N=1/2 Supersymmetric Gauge Theory
We extend the instanton calculus for N=1/2 U(2) supersymmetric gauge theory
by including one massless flavor. We write the equations of motion at leading
order in the coupling constant and we solve them exactly in the
non(anti)commutativity parameter C. The profile of the matter superfield is
deformed through linear and quadratic corrections in C. Higher order
corrections are absent because of the fermionic nature of the back-reaction.
The instanton effective action, in addition to the usual 't Hooft term,
includes a contribution of order C^2 and is N=1/2 invariant. We argue that the
N=1 result for the gluino condensate is not modified by the presence of the new
term in the effective action.Comment: 33 pages, harvmac; v2: minor changes, added references; v3: added
analysis of the instanton measure in section
Inflammation as a therapeutic target in atherosclerosis
Atherosclerotic coronary artery disease (CAD) results from build-up of cholesterol-rich plaques in the walls of the coronary arteries and is a leading cause of death. Inflammation is central to atherosclerosis. Uncontrolled inflammation makes coronary plaques "unstable" and vulnerable to rupture or erosion, leading to thrombosis and myocardial infarction (MI). As multiple inflamed plaques often co-exist in the coronary system, patients are at risk of repeated atherothrombotic cardiovascular events after MI, with rates of 10-12% at one year and 18-20% at three years. This is largely because current therapies for CAD, such as lipid-lowering statins, do not adequately control plaque inflammation. New anti-atherosclerotic agents are therefore needed, especially those that better target inflammation. The recent positive results for the anti-interleukin-1-beta (IL-1β) monoclonal antibody, Canakinumab, in the Canakinumab Anti-inflammatory Thrombosis Outcome Study (CANTOS) clinical trial has provided a major stimulant to the field. It highlights that not only is inflammation important from a pathogenic and risk prediction perspective in CAD, but that reducing inflammation can be beneficial. The challenge is now to find the best strategies to achieve this in real-world practice. This review outlines the role that inflammation plays in atherosclerosis and provides an update on anti-inflammatory therapies currently being investigated to target atherosclerosis.Mau T Nguyen, Sanuja Fernando, Nisha Schwarz, Joanne TM Tan, Christina A Bursill and Peter J Psalti
Black Holes, Branes and Superconformal Symmetry
The main focus of this lecture is on extended objects in adS*S bosonic
backgrounds with unbroken supersymmetry. The backgrounds are argued to be
exact, special consideration are given to the non-maximal supersymmetry case.
The near horizon superspace construction is explained. The superconformal
symmetry appears in the worldvolume actions as the superisometry of the near
horizon superspace, like the superPoincare symmetry of GS superstring and BST
supermembrane in the flat superspace. The issues in gauge fixing of local
kappa-symmetry are reviewed. We describe the features of the gauge-fixed IIB
superstring in adS(5)*S(5) background with RR 5-form. From a truncated boundary
version of it we derive an analytic N=2 off shell harmonic superspace of
Yang-Mills theory. The reality condition of the analytic subspace, which
includes the antipodal map on the sphere, has a simple meaning of the symmetry
of the string action in the curved space. The relevant issues of black holes
and superconformal mechanics are addressed.Comment: 34 pages, Latex. To be published in the Proceedings of a conference
held in Corfu, Greece in September 1998. Improvement in Sec. 3.
Comments on Gluino Condensates in N=1/2 SYM Theory
Using Ward identities of N=1/2 supersymmetric Yang-Mills theory, we show that
while the partition function and antichiral gluino condensates remain invariant
under the deformation, chiral gluino correlators can get contributions from
all gauge fields with instanton numbers . In particular, a Ward
identity of the symmetry allows us to determine the explicit
dependence of chiral gluino correlators on the deformation parameter.Comment: 11 pages, 4 figures, small changes, added a referenc
Instanton Calculations for N=1/ 2 super Yang-Mills Theory
We study (anti-) instantons in super Yang-Mills theories defined on a non
anticommutative superspace. The instanton solution that we consider is the same
as in ordinary SU(2) N=1 super Yang-Mills, but the anti-instanton receives
corrections to the U(1) part of the connection which depend quadratically on
fermionic coordinates, and linearly on the deformation parameter C. By
substituting the exact solution into the classical Lagrangian the topological
charge density receives a new contribution which is quadratic in C and quartic
in the fermionic zero-modes. The topological charge turns out to be zero. We
perform an expansion around the exact classical solution in presence of a
fermionic background and calculate the full superdeterminant contributing to
the one-loop partition function. We find that the one-loop partition function
is not modified with respect to the usual N=1 super Yang-Mills.Comment: 27 pages, harmvac, Redone the computation of topological charge, a
section has been rewritten and references adde
Chiral effective potential in non-commutative Wess-Zumino model
We study a structure of holomorphic quantum contributions to the effective
action for noncommutative Wess-Zumino model. Using the symbol
operator techniques we present the one-loop chiral effective potential in a
form of integral over proper time of the appropriate heat kernel. We prove that
this kernel can be exactly found. As a result we obtain the exact integral
representation of the one-loop effective potential. Also we study the expansion
of the effective potential in a series in powers of the chiral superfield
and derivative and construct a procedure for systematic
calculation of the coefficients in the series. We show that all terms in the
series without derivatives can be summed up in an explicit form.Comment: LaTeX, JHEP style, 32 pages, typos corrected, references adde
N=2 Supersymmetric U(1) Gauge Theory in Noncommutative Harmonic Superspace
We study N=2 supersymmetric U(1) gauge theory in the noncommutative harmonic
superspace with nonanticommutative fermionic coordinates. We examine the gauge
transformation which preserves the Wess-Zumino gauge by harmonic expansions of
component fields. The gauge transformation is shown to depend on the
deformation parameters and the anti-holomorphic scalar field. We compute the
action explicitly up to the third order in component fields and discuss the
field redefinitions so that the component fields transform canonically.Comment: 42 pages, LaTeX, v2: references added, v3: minor correction
N=1/2 Super Yang-Mills Theory on Euclidean AdS2xS2
We study D-branes in the background of Euclidean AdS2xS2 with a graviphoton
field turned on. As the background is not Ricci flat, the graviphoton field
must have both self-dual and antiself-dual parts. This, in general, will break
all the supersymmetries on the brane. However, we show that there exists a
limit for which one can restore half of the supersymmetries. Further, we show
that in this limit, the N=1/2 SYM Lagrangian on flat space can be lifted on to
the Euclidean AdS2xS2 preserving the same amount of supersymmetries as in the
flat case. We observe that without the C-dependent terms present in the action
this lift is not possible.Comment: 12 pages, latex file; v2: minor corrections, references adde
Effects of metallic spacer in layered superconducting Sr2(MgTi)O3FeAs
The highly two-dimensional superconducting system
Sr2(MgTi)O3FeAs, recently synthesized in the range of 0.2 < y <
0.5, shows an Mg concentration-dependent . Reducing the Mg concentration
from y=0.5 leads to a sudden increase in , with a maximum ~40 K at
y=0.2. Using first principles calculations, the unsynthesized stoichiometric
y=0 and the substoichiometric y=0.5 compounds have been investigated. For the
50% Mg-doped phase (y=0.5), Sr2(MgTi)O3 layers are completely
insulating spacers between FeAs layers, leading to the fermiology such as that
found for other Fe pnictides. At y=0, representing a phase with metallic
Sr2TiO3 layers, the -centered Fe-derived Fermi surfaces (FSs)
considerably shrink or disappear. Instead, three -centered Ti FSs
appear, and in particular two of them have similar size, like in MgB2.
Interestingly, FSs have very low Fermi velocity in large fractions: the lowest
being 0.6 cm/s. Furthermore, our fixed spin moment calculations
suggest the possibility of magnetic ordering, with magnetic Ti and nearly
nonmagnetic Fe ions. These results indicate a crucial role of
Sr2(MgTi)O3 layers in this superconductivity.Comment: 7 pages; Proceedings of ICSM-201
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