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Yosuke Imamura

Publications and source records attributed to Yosuke Imamura.

At least 37 records · Page 2Linked to original sources
arXiv2018

Codimension-2 brane solutions of maximal supergravities in 9, 8, and 7 dimensions

We construct codimension-2 BPS brane solutions in $D=9,8,7$ maximal supergravities by solving Killing spinor equations. We assume the Poincare invariance along the worldvolume and vanishing gauge fields, and determine the metric and the scalar fields. The solution in $D=9$ is essentially the same as the ten-dimensional one, which is specified by a holomorphic function in the transverse space. For $D=8$, the solution is specified by two holomorphic functions, and regarded as $T^2\times T^2$ compactification of F-theory. For $D=7$, we find that the solution can be interpreted as M-theory on Calabi-Yau, and under an additional assumption a solution is specified by two holomorphic functions.

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arXiv2018

Orbifold Schur Index and IR formula

We discuss orbifold version of the Schur index defined as the supersymmetric partition function in S^3/Z_n x S^1. We first give a general formula for Lagrangian theories obtained by localization technique, and then suggest a generalization of the Cordova and Shao's IR formula. We confirm the generalized IR formula gives the correct answer for systems with free hypermultiplets if we tune the background fields so that they are invariant under the orbifold action. Unfortunately, we find disagreement for theories with dynamical vector multiplets.

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arXiv2016

Superconformal index of N=3 orientifold theories

We analyze the superconformal index of the N=3 supersymmetric Z_k generalized orientifold theories recently proposed. In the large N limit we derive the index from the Kaluza-Klein modes in AdS_5 x S^5/Z_k, which are obtained from ones in AdS_5 x S^5 by a simple projection. For the ordinary Z_2 orientifold case the agreement with the gauge theory calculation is explicitly confirmed, and for Z_k with k > 2 we perform a few consistency checks with known results for N=3 theories. We also study finite N corrections by analyzing wrapped D3-branes and discrete torsions in the dual geometry.

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arXiv2016

Supersymmetry Enhancement and Junctions in S-folds

We study supersymmetry enhancement from ${\cal N}=3$ to ${\cal N}=4$ 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 $Z$ and $\bar Z$. The S-fold projection eliminates $\bar Z$ as well as one of the four supercharges, and when the supersymmetry is enhanced $\bar Z$ should be reproduced by some non-perturbative mechanism. For the models of $\mathbb{Z}_3$ and $\mathbb{Z}_4$ S-folds which are expected to give $SU(3)$ and $SO(5)$ ${\cal N}=4$ theories we compare the junction spectra with those in perturbative brane realization of the same theories. We establish one-to-one correspondence so that $Z$ coincides. By using the correspondence we also give an expression for the enhanced central charge $\bar Z$.

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arXiv2015

Index calculation by means of harmonic expansion

We review derivation of superconformal indices by means of supersymmetric localization and spherical harmonic expansion for 3d N=2, 4d N=1, and 6d N=(1,0) supersymmetric gauge theories. We demonstrate calculation of indices for vector multiplets in each dimensions by analysing energy eigenmodes in S^pxR. For the 6d index we consider the perturbative contribution only. We put focus on technical details of harmonic expansion rather than physical applications.

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arXiv2014

Factorization of S^3/Z_n partition function

We investigate S^3/Z_n partition function of 3d N = 2 supersymmetric field theories. In a gauge theory the partition function is the sum of the contributions of sectors specified by holonomies, and we should carefully choose the relative signs among the contributions. We argue that the factorization to holomorphic blocks is a useful criterion to determine the signs and propose a formula for them. We show that the orbifold partition function of a general non-gauge theory is correctly factorized provided that we take appropriate relative signs. We also present a few examples of gauge theories. We point out that the sign factor for the orbifold partition function is closely related to a similar sign factor in the lens space index and the 3d index.

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arXiv2014

Supersymmetric backgrounds from 5d N=1 supergravity

We construct curved backgrounds with Euclidean signature admitting rigid supersymmetry by using a 5d N=1 off-shell Poincare supergravity. We solve the conditions for the background Weyl multiplet and vector multiplets that preserve at least one supersymmetry parameterized by a symplectic Majorana spinor, and represent the solution in terms of several independent fields. We also show that the partition function does not depends on the local degrees of freedom of the background fields. Namely, as far as we focus on a single coordinate patch, we can freely change the independent fields by combining Q-exact deformations and gauge transformations. We also discuss realization of several known examples of supersymmetric theories in curved backgrounds by using the supergravity.

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arXiv2013

Perturbative partition function for a squashed S^5

We compute the index of 6d N=(1,0) theories on S^5 x R containing vector and hypermultiplets. We only consider the perturbative sector without instantons. By compactifying R to S^1 with a twisted boundary condition and taking the small radius limit, we derive the perturbative partition function on a squashed S^5. The 1-loop partition function is represented in a simple form with the triple sine function.

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arXiv2012

Supersymmetric theories on squashed five-sphere

We construct supersymmetric theories on the SU(3)xU(1) symmetric squashed five-sphere with 2, 4, 6, and 12 supercharges. We first determine the Killing equation by dimensional reduction from 6d, and use Noether procedure to construct actions. The supersymmetric Yang-Mills action is straightforwardly obtained from the supersymmetric Chern-Simons action by using a supersymmetry preserving constant vector multiplet.

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arXiv2012

S^3/Z_n partition function and dualities

We investigate S^3/Z_n partition function of N = 2 supersymmetric gauge theories. A gauge theory on the orbifold has degenerate vacua specified by the holonomy. The partition function is obtained by summing up the contributions of saddle points with different holonomies. An appropriate choice of the phase of each contribution is essential to obtain the partition function. We determine the relative phases in the holonomy sum in a few examples by using duality to non-gauge theories. In the case of odd n the phase factors can be absorbed by modifying a single function appearing in the partition function.

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arXiv2012

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.

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arXiv2011

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.

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arXiv2011

Relation between the 4d superconformal index and the S^3 partition function

A relation between the 4d superconformal index and the S^3 partition function is studied with focus on the 4d and 3d actions used in localization. In the case of vanishing Chern-Simons levels and round S^3 we explicitly show that the 3d action is obtained from the 4d action by dimensional reduction up to terms which do not affect the exact results. By combining this fact and a recent proposal concerning a squashing of S^3 and SU(2) Wilson line, we obtain a formula which gives the partition function depending on the Weyl weight of chiral multiplets, real mass parameters, FI parameters, and a squashing parameter as a limit of the index of a parent 4d theory.

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arXiv2011

Boundary state of superstring in open string channel

We derive boundary state of superstring in the open string channel. It describes the superconformal field theory of open string emission and absorption by D-brane. We define the boundary state by conformal mappings from upper half plane with operators inserted at two points corresponding to the corners of semi-infinite strip. We obtain explicit oscillator forms analytically for the fermion and superconformal ghost sectors. For the fermion sector we compare this with numerical result obtained by using naive boundary condition.

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arXiv2011

Twisted Sectors in Gravity Duals of N=4 Chern-Simons Theories

We study Kaluza-Klein modes of a d=7, N=2 vector multiplet in AdS_4 x S^3. Such modes arise in the context of AdS/CFT as dual objects of a class of gauge invariant operators in N=4 Chern-Simons theories. We confirm that the Kaluza-Klein modes precisely reproduce the BPS spectrum of the operators.

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arXiv2009

A Monopole Index for N=4 Chern-Simons Theories

We compute a certain index for an N=4 Chern-Simons theory with gauge group U(N)^r in the large N limit with taking account of monopole contribution, and compare it to the corresponding multi-particle index for M-theory in the dual geometry AdS_4 x X_7. The internal space X_7 has non-trivial two-cycles, and M2-branes wrapped on them contribute to the multi-particle index. We establish one-to-one map between r-1 independent magnetic charges on the gauge theory side and the same number of charges on the gravity side: the M-momentum and r-2 (=b_2(X_7)) wrapping numbers. With a certain assumption for the wrapped M2-brane contribution, we confirm the agreement of the indices for many sectors specified by the r-1 charges by using analytic and numerical methods.

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arXiv2009

Charges and homologies in AdS_4/CFT_3

Electric and magnetic charges of a certain class of operators in N=2 large N quiver Chern-Simons theories are investigated. We consider only non-chiral theories, in which every bi-fundamental field appears with its conjugate representation. By interpreting operators in a Chern-Simons theory as wrapped M-branes in the dual geometry AdS_4 x X_7, we partly determine the homologies of X_7.

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