3,344 research outputs found
One-loop Correction and the Dilaton Runaway Problem
We examine the one-loop vacuum structure of an effective theory of gaugino
condensation coupled to the dilaton for string models in which the gauge
coupling constant does not receive string threshold corrections. The new
ingredients in our treatment are that we take into account the one-loop
correction to the dilaton K\"ahler potential and we use a formulation which
includes a chiral field corresponding to the gaugino bilinear. We find
through explicit calculation that supersymmetry in the Yang-Mills sector is
broken by gaugino condensation.
The dilaton and field have masses on the order of the gaugino
condensation scale independently of the dilaton VEV. Although the calculation
performed here is at best a model of the full gaugino condensation dynamics,
the result shows that the one-loop correction to the dilaton K\"ahler potential
as well as the detailed dynamics at the gaugino condensation scale may play an
important role in solving the dilaton runaway problem.Comment: 19 page
Supersymmetric IIB Solutions with Schr\"{o}dinger Symmetry
We find a class of non-relativistic supersymmetric solutions of IIB
supergravity with non-trivial B-field that have dynamical exponent n=2 and are
invariant under the Schrodinger group. For a general Sasaki-Einstein internal
manifold with U(1)^3 isometry, the solutions have two real supercharges. When
the internal manifold is S^5, the number of supercharges can be four. We also
find a large class of non-relativistic scale invariant type IIB solutions with
dynamical exponents different from two. The explicit solutions and the values
of the dynamical exponents are determined by vector eigenfunctions and
eigenvalues of the Laplacian on an Einstein manifold.Comment: 28 pages, LaTe
Short distance properties of cascading gauge theories
We study the short distance (large momentum) properties of correlation
functions of cascading gauge theories by performing a tree-level computation in
their dual gravitational background. We prove that these theories are
holographically renormalizable; the correlators have only analytic ultraviolet
divergences, which may be removed by appropriate local counterterms. We find
that n-point correlation functions of properly normalized operators have the
expected scaling in the semi-classical gravity (large N) limit: they scale as
N_{eff}^{2-n} with N_{eff} proportional to ln(k/Lambda) where k is a typical
momentum. Our analysis thus confirms the interpretation of the cascading gauge
theories as renormalizable four-dimensional quantum field theories with an
effective number of degrees of freedom which logarithmically increases with the
energy.Comment: 47 pages, no figure
When is rotational angiography superior to conventional single-plane angiography for planning coronary angioplasty?
Objectives: To investigate the value of rotational coronary angiography (RoCA) in the context of percutaneous coronary intervention (PCI) planning.
Background: As a diagnostic tool, RoCA is associated with decreased patient irradiation and contrast use compared with conventional coronary angiography (CA) and provides superior appreciation of three-dimensional anatomy. However, its value in PCI remains unknown.
Methods: We studied stable coronary artery disease assessment and PCI planning by interventional cardiologists. Patients underwent either RoCA or conventional CA pre-PCI for planning. These were compared with the referral CA (all conventional) in terms of quantitative lesion assessment and operator confidence. An independent panel reanalyzed all parameters.
Results: Six operators performed 127 procedures (60 RoCA, 60 conventional CA, and 7 crossed-over) and assessed 212 lesions. RoCA was associated with a reduction in the number of lesions judged to involve a bifurcation (23 vs. 30 lesions, P < 0.05) and a reduction in the assessment of vessel caliber (2.8 vs. 3.0 mm, P < 0.05). RoCA improved confidence assessing lesion length (P = 0.01), percentage stenosis (P = 0.02), tortuosity (P < 0.04), and proximity to a bifurcation (P = 0.03), particularly in left coronary artery cases. X-ray dose, contrast agent volume, and procedure duration were not significantly different.
Conclusions: Compared with conventional CA, RoCA augments quantitative lesion assessment, enhances confidence in the assessment of coronary artery disease and the precise details of the proposed procedure, but does not affect X-ray dose, contrast agent volume, or procedure duration. © 2015 Wiley Periodicals, Inc
The transfer of fibres in the carding machine
The problem of understanding the transfer of fibres between carding-machine surfaces is addressed by considering the movement of a single fibre in an airflow. The structure of the aerodynamic flow field predicts how and when fibres migrate between the different process surfaces. In the case of a revolving-flats carding machine the theory predicts a “strong” aerodynamic mechanism between taker-in and cylinder and a “weak” mechanism between cylinder and removal cylinder resulting in effective transfer in the first case and a more limited transfer in the second
General 2 charge geometries
Two charge BPS horizon free supergravity geometries are important in
proposals for understanding black hole microstates. In this paper we construct
a new class of geometries in the NS1-P system, corresponding to solitonic
strings carrying fermionic as well as bosonic condensates. Such geometries are
required to account for the full microscopic entropy of the NS1-P system. We
then briefly discuss the properties of the corresponding geometries in the dual
D1-D5 system.Comment: 44 page
Strings between branes
D-brane configurations containing fundamental strings are constructed as
classical solutions of Yang-Mills theory. The fundamental strings in these
systems stretch between D-branes. In the case of D1-branes, this construction
gives smooth (classical) resolutions of string junctions and string networks.
Using a non-abelian Yang-Mills analysis of the string current, the string
charge density is computed and is shown to have support in the region between
the D-brane world-volumes. The 't Hooft-Polyakov monopole is analyzed using
similar methods, and is shown to contain D-strings whose flux has support off
the D-brane world-volume defined by the Higgs scalar field, when this field is
interpreted in terms of a transverse dimension. The constructions presented
here are used to give a qualitative picture of tachyon condensation in the
Yang-Mills limit, where fundamental strings and lower-dimensional D-branes
arise in a volume of space-time where brane-antibrane annihilation has
occurred.Comment: 35 pages, 16 eps figures, JHEP style; v2: a comment adde
Vacuolar and plasma membrane stripping and autophagic elimination of Toxoplasma gondii in primed effector macrophages
Apicomplexan protozoan pathogens avoid destruction and establish a replicative niche within host cells by forming a nonfusogenic parasitophorous vacuole (PV). Here we present evidence for lysosome-mediated degradation of Toxoplasma gondii after invasion of macrophages activated in vivo. Pathogen elimination was dependent on the interferon Îł inducible-p47 GTPase, IGTP, required PI3K activity, and was preceded by PV membrane indentation, vesiculation, disruption, and, surprisingly, stripping of the parasite plasma membrane. Denuded parasites were enveloped in autophagosome-like vacuoles, which ultimately fused with lysosomes. These observations outline a series of mechanisms used by effector cells to redirect the fate of a classically nonfusogenic intracellular pathogen toward a path of immune elimination
Some No-go Theorems for String Duals of Non-relativistic Lifshitz-like Theories
We study possibilities of string theory embeddings of the gravity duals for
non-relativistic Lifshitz-like theories with anisotropic scale invariance. We
search classical solutions in type IIA and eleven-dimensional supergravities
which are expected to be dual to (2+1)-dimensional Lifshitz-like theories.
Under reasonable ansaetze, we prove that such gravity duals in the
supergravities are not possible. We also discuss a possible physical reason
behind this.Comment: 18 pages, Latex, flux conditions clarified (v2), brief summary of
results added (v3
Type IIA Moduli Stabilization
We demonstrate that flux compactifications of type IIA string theory can
classically stabilize all geometric moduli. For a particular orientifold
background, we explicitly construct an infinite family of supersymmetric vacua
with all moduli stabilized at arbitrarily large volume, weak coupling, and
small negative cosmological constant. We obtain these solutions from both
ten-dimensional and four-dimensional perspectives. For more general
backgrounds, we study the equations for supersymmetric vacua coming from the
effective superpotential and show that all geometric moduli can be stabilized
by fluxes. We comment on the resulting picture of statistics on the landscape
of vacua.Comment: 48 pages, 2 figures, LaTeX. v2: references added. v3: minor comments
& references adde
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