17,967 research outputs found
Perturbing Around A Warped Product Of AdS_4 and Seven-Ellipsoid
We compute the spin-2 Kaluza-Klein modes around a warped product of AdS_4 and
a seven-ellipsoid. This background with global G_2 symmetry is related to a
U(N) x U(N) N=1 superconformal Chern-Simons matter theory with sixth order
superpotential. The mass-squared in AdS_4 is quadratic in G_2 quantum number
and KK excitation number. We determine the dimensions of spin-2 operators using
the AdS/CFT correspondence. The connection to N=2 theory preserving SU(3) x
U(1)_R is also discussed.Comment: 21pp; The second and last paragraphs of section 2, the footnotes 1
and 2 added and to appear in JHE
Geometrically Induced Phase Transitions at Large N
Utilizing the large N dual description of a metastable system of branes and
anti-branes wrapping rigid homologous S^2's in a non-compact Calabi-Yau
threefold, we study phase transitions induced by changing the positions of the
S^2's. At leading order in 1/N the effective potential for this system is
computed by the planar limit of an auxiliary matrix model. Beginning at the two
loop correction, the degenerate vacuum energy density of the discrete confining
vacua split, and a potential is generated for the axion. Changing the relative
positions of the S^2's causes discrete jumps in the energetically preferred
confining vacuum and can also obstruct direct brane/anti-brane annihilation
processes. The branes must hop to nearby S^2's before annihilating, thus
significantly increasing the lifetime of the corresponding non-supersymmetric
vacua. We also speculate that misaligned metastable glueball phases may
generate a repulsive inter-brane force which stabilizes the radial mode present
in compact Calabi-Yau threefolds.Comment: 47 pages, 7 figure
ZZ-Branes of N=2 Super-Liouville Theory
We study conformal boundary conditions and corresponding one-point functions
of the N=2 super-Liouville theory using both conformal and modular bootstrap
methods. We have found both continuous (`FZZT-branes') and discrete
(`ZZ-branes') boundary conditions. In particular, we identify two different
types of the discrete ZZ-brane solutions, which are associated with degenerate
fields of the N=2 super-Liouville theory.Comment: 26 page
Cosmological Lower Bound on Dark Matter Masses from the Soft Gamma-ray Background
Motivated by a recent detection of 511 keV photons from the center of our
Galaxy, we calculate the spectrum of the soft gamma-ray background of the
redshifted 511 keV photons from cosmological halos. Annihilation of dark matter
particles into electron-positron pairs makes a substantial contribution to the
gamma-ray background. Mass of such dark matter particles must be <~ 100 MeV so
that resulting electron-positron pairs are on-relativistic. On the other hand,
we show that in order for the annihilation not to exceed the observed
background, the dark matter mass needs to be >~ 20 MeV. We include the
contribution from the active galactic nuclei and supernovae. The halo
substructures may increase the lower bound to >~ 60 MeV.Comment: 5 pages, 5 figures; accepted for publication in PRD, Rapid
Communicatio
Effect of Electron Beam Irradiation and Storage on the Quality Attributes of Sausages with Different Fat Contents
Sausages with different fat contents (16 or 29%) were purchased from local stores, vacuum-packaged in oxygen-impermeable bags, and irradiated at 0 or 5 kGy using a linear accelerator. The changes in quality attributes of irradiated sausages were determined during storage at 4°C. The 2-thiobarbituric acid-reactive substance values of sausages were not affected by fat content but were increased after irradiation (5 kGy). Storage for 60 d increased the 2-thiobarbituric acid-reactive substance values of nonirradiated sausages (P \u3c 0.05) but had no effect on irradiated sausages. The numbers of volatile compounds and the amounts of total volatiles were increased by irradiation in both the high-fat (29% fat) and low-fat (16% fat) sausages. Dimethyl sulfide was detected only in irradiated sausages, regardless of fat content (P \u3c 0.05), but it disappeared after 60 d of storage. Pentane and 1-heptene were detected only in irradiated samples after 60 d of storage. Low-fat sausages had greater L* values, but had lesser a* and b* values than high-fat sausages. Irradiation and storage had little effect on either the exterior or interior color (L*, a*, and b* values) of sausages. Fat content had no effect on the sensory variables of sausages, regardless of irradiation and storage. However, irradiated sausages had significantly stronger off-odors and off-flavors than nonirradiated sausages regardless of fat content (P \u3c 0.05). This indicated that fat content in sausages had a minimal effect on the quality of irradiated sausages during storage
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