583 research outputs found
Superconformal index for large N quiver Chern-Simons theories
We investigate the N=2 superconformal index for supersymmetric quiver
Chern-Simons theories with large N gauge groups. After general arguments about
the large N limit, we compute the first few terms in the series expansion of
the index for theories proposed as dual theories to homogeneous spaces V^{5,2},
Q^{1,1,1}, Q^{2,2,2}, M^{1,1,1}, and N^{0,1,0}. We confirm that the indices
have symmetries expected from the isometries of dual manifolds.Comment: 27 pages, 7 figures; v2: typos corrected, Sec.6 modified; v3:
explanation improved, minor corrections, version published in JHE
N=2 supersymmetric theories on squashed three-sphere
We investigate a squashing deformation of 3d N=2 supersymmetric theories on
three-sphere, which have four supercharges. The deformation preserves SU(2)_L x
U(1)_r isometry and all four supersymmetries. We compute the partition function
and find non-trivial dependence on the squashing parameter. We also consider
the large N limit of a certain class of quiver gauge theories which have free
energy of order N^{3/2}, and show that the free energy on the squashed sphere
differs from that on round sphere by a certain factor depending only on the
squashing parameter.Comment: 39 pages, 2 figures, v2: minor corrections, references added; v3:
minor correction
Geometric free energy of toric AdS4/CFT3 models
We study the supersymmetric free energy of three dimensional
Chern-Simons-matter theories holographically dual to AdS times toric
Sasaki-Einstein seven-manifolds. In the large limit, we argue that the
square of the free energy can be written as a quartic polynomial of trial
R-charges. The coefficients of the polynomial are determined geometrically from
the toric diagrams. We present the coefficients of the quartic polynomial
explicitly for generic toric diagrams with up to 6 vertices, and some
particular diagrams with 8 vertices. Decomposing the trial R-charges into
mesonic and baryonic variables, and eliminating the baryonic ones, we show that
the quartic polynomial reproduces the inverse of the Martelli-Sparks-Yau volume
function. On the gravity side, we explore the possibility of using the same
quartic polynomial as the prepotential in the AdS gauged supergravity.
Comparing Kaluza-Klein gravity and gauged supergravity descriptions, we find
perfect agreement in the mesonic sector but some discrepancy in the baryonic
sector.Comment: 39 pages, 21 figures; v2. references added, minor improvement
Parity Violation of Gravitons in the CMB Bispectrum
We investigate the cosmic microwave background (CMB) bispectra of the
intensity (temperature) and polarization modes induced by the graviton
non-Gaussianities, which arise from the parity-conserving and parity-violating
Weyl cubic terms with time-dependent coupling. By considering the
time-dependent coupling, we find that even in the exact de Sitter space time,
the parity violation still appears in the three-point function of the
primordial gravitational waves and could become large. Through the estimation
of the CMB bispectra, we demonstrate that the signals generated from the
parity-conserving and parity-violating terms appear in completely different
configurations of multipoles. For example, the parity-conserving
non-Gaussianity induces the nonzero CMB temperature bispectrum in the
configuration with and, while due to the
parity-violating non-Gaussianity, the CMB temperature bispectrum also appears
for . This signal is just good evidence of the
parity violation in the non-Gaussianity of primordial gravitational waves. We
find that the shape of this non-Gaussianity is similar to the so-called
equilateral one and the amplitudes of these spectra at large scale are roughly
estimated as , where is an energy scale that
sets the magnitude of the Weyl cubic terms (higher derivative corrections) and
is a tensor-to-scalar ratio. Taking the limit for the nonlinearity
parameter of the equilateral type as , we can obtain
a bound as , assuming .Comment: 23 pages, 3 figures. Accepted for publication in PTP. Version 3
includes errata in Fig.
Supersymmetry Enhancement and Junctions in S-folds
We study supersymmetry enhancement from to proposed
by Aharony and Tachikawa by using string junctions in S-folds. The central
charges carried by junctions play a central role in our analysis. We consider
planer junctions in a specific plane. Before the S-folding they carry two
complex central charges, which we denote by and . The S-fold
projection eliminates as well as one of the four supercharges, and
when the supersymmetry is enhanced should be reproduced by some
non-perturbative mechanism. For the models of and
S-folds which are expected to give and theories we
compare the junction spectra with those in perturbative brane realization of
the same theories. We establish one-to-one correspondence so that
coincides. By using the correspondence we also give an expression for the
enhanced central charge .Comment: 30 pages, 7 figures, v2: minor corrections, version accepted for
publication in JHE
Constraining modified theory of gravity with galaxy bispectrum
We explore the use of galaxy bispectrum induced by the nonlinear
gravitational evolution as a possible probe to test general scalar-tensor
theories with second-order equations of motion. We find that time dependence of
the leading second-order kernel is approximately characterized by one
parameter, the second-order index, which is expected to trace the higher-order
growth history of the Universe. We show that our new parameter can
significantly carry new information about the non-linear growth of structure.
We forecast future constraints on the second-order index as well as the
equation-of-state parameter and the growth index.Comment: 15 pages, 2 figure
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