13,656 research outputs found
Nonperturbative Formulas for Central Functions of Supersymmetric Gauge Theories
For quantum field theories that flow between ultraviolet and infrared fixed
points, central functions, defined from two-point correlators of the stress
tensor and conserved currents, interpolate between central charges of the UV
and IR critical theories. We develop techniques that allow one to calculate the
flows of the central charges and that of the Euler trace anomaly coefficient in
a general N=1 supersymmetric gauge theory. Exact, explicit formulas for
gauge theories in the conformal window are given and analysed. The
Euler anomaly coefficient always satisfies the inequality .
This is new evidence in strongly coupled theories that this quantity satisfies
a four-dimensional analogue of the -theorem, supporting the idea of
irreversibility of the RG flow. Various other implications are discussed.Comment: latex, 27 page
Parametric evaluation of ball milling of SiC in water
A statistically designed experiment was conducted to determine optimum conditions for ball milling alpha-SiC in water. The influence of pH adjustment, volume percent solids loading, and mill rotational speed on grinding effectiveness was examined. An equation defining the effect of those milling variables on specific surface area was obtained. The volume percent solids loading of the slurry had the greatest influence on the grinding effectiveness in terms of increase in specific surface area. As grinding effectiveness improved, mill and media wear also increased. Contamination was minimized by use of sintered alpha-SiC milling hardware
Particle size reduction of Si3N4 with Si3N4 milling hardware
The grinding of Si3N4 powder using reaction bonded Si3N4 attrition, vibratory, and ball mills with Si3N4 media was examined. The rate of particle size reduction and the change in the chemical composition of the powder were determined in order to compare the grinding efficiency and the increase in impurity content resulting from mill and media wear for each technique. Attrition and vibratory milling exhibited rates of specific surface area increase that were approximately eight times that observed in ball milling. Vibratory milling introduced the greatest impurity pickup
The dual of Janus -:- an interface CFT
We propose and study a specific gauge theory dual of the smooth,
non-supersymmetric (and apparently stable) Janus solution of Type IIB
supergravity found in hep-th/0304129. The dual field theory is N=4 SYM theory
on two half-spaces separated by a planar interface with different coupling
constants in each half-space. We assume that the position dependent coupling
multiplies the operator L' which is the fourth descendent of the primary Tr(X^I
X^J) and closely related to the N=4 Lagrangian density. At the classical level
supersymmetry is broken explicitly, but SO(3,2) conformal symmetry is
preserved. We use conformal perturbation theory to study various correlation
functions to first and second order in the discontinuity of g^2_{YM},
confirming quantum level conformal symmetry. Certain quantities such as the
vacuum expectation value are protected to all orders in g^2_{YM}N, and we
find perfect agreement between the weak coupling value in the gauge theory and
the strong coupling gravity result. SO(3,2) symmetry requires vanishing vacuum
energy, =0, and this is confirmed in first order in the
discontinuity.Comment: 24 pages, 1 figure; references adde
Holographic RG-flows and Boundary CFTs
Solutions of -dimensional gravity coupled to a scalar field are
obtained, which holographically realize interface and boundary CFTs. The
solution utilizes a Janus-like slicing ansatz and corresponds
to a deformation of the CFT by a spatially-dependent coupling of a relevant
operator. The BCFT solutions are singular in the bulk, but physical quantities
such as the holographic entanglement entropy can be calculated.Comment: 26 pages, 11 figure
From Soft Walls to Infrared Branes
Five dimensional warped spaces with soft walls are generalizations of the
standard Randall-Sundrum compactifications, where instead of an infrared brane
one has a curvature singularity (with vanishing warp factor) at finite proper
distance in the bulk. We project the physics near the singularity onto a
hypersurface located a small distance away from it in the bulk. This results in
a completely equivalent description of the soft wall in terms of an effective
infrared brane, hiding any singular point. We perform explicitly this
calculation for two classes of soft wall backgrounds used in the literature.
The procedure has several advantages. It separates in a clean way the physics
of the soft wall from the physics of the five dimensional bulk, facilitating a
more direct comparison with standard two-brane warped compactifications.
Moreover, consistent soft walls show a sort of universal behavior near the
singularity which is reflected in the effective brane Lagrangian. Thirdly, for
many purposes, a good approximation is obtained by assuming the bulk background
away from the singularity to be the usual Randall-Sundrum metric, thus making
the soft wall backgrounds better analytically tractable. We check the validity
of this procedure by calculating the spectrum of bulk fields and comparing it
to the exact result, finding very good agreement.Comment: 14 pages, 2 figures, v2: subsection on IR brane potentials and
appendix on fermions added, version to appear in PR
Supersymmetry algebra in N = 1 chiral supergravity
We consider the supersymmetry (SUSY) transformations in the chiral Lagrangian
for supergravity (SUGRA) with the complex tetrad following the method
used in the usual SUGRA, and present the explicit form of the SUSY
trasformations in the first-order form. The SUSY transformations are generated
by two independent Majorana spinor parameters, which are apparently different
from the constrained parameters employed in the method of the 2-form gravity.
We also calculate the commutator algebra of the SUSY transformations on-shell.Comment: 10 pages, late
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