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Search Results: 1 - 10 of 1152 matches for " Takuya Okuda "
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The Equality of Solutions in Vacuum String Field Theory
Takuya Okuda
Physics , 2002, DOI: 10.1016/S0550-3213(02)00615-6
Abstract: We analytically prove that the matter solution of vacuum string field theory constructed by Kostelecky and Potting is the matter sliver state. We also give an analytical proof that the ghost solution by Hata and Kawano is the sliver state in the twisted ghost CFT. It is also proved that the candidate state for the tachyon proposed by Hata and Kawano can be identified with the state constructed by Rastelli, Sen and Zwiebach using CFT. Our proofs are based on the techniques recently developed by Okuyama.
D-branes as a Bubbling Calabi-Yau
Jaume Gomis,Takuya Okuda
Mathematics , 2007, DOI: 10.1088/1126-6708/2007/07/005
Abstract: We prove that the open topological string partition function on a D-brane configuration in a Calabi-Yau manifold X takes the form of a closed topological string partition function on a different Calabi-Yau manifold X_b. This identification shows that the physics of D-branes in an arbitrary background X of topological string theory can be described either by open+closed string theory in X or by closed string theory in X_b. The physical interpretation of the ''bubbling'' Calabi-Yau X_b is as the space obtained by letting the D-branes in X undergo a geometric transition. This implies, in particular, that the partition function of closed topological string theory on certain bubbling Calabi-Yau manifolds are invariants of knots in the three-sphere.
Wilson Loops, Geometric Transitions and Bubbling Calabi-Yau's
Jaume Gomis,Takuya Okuda
Mathematics , 2006, DOI: 10.1088/1126-6708/2007/02/083
Abstract: Motivated by recent developments in the AdS/CFT correspondence, we provide several alternative bulk descriptions of an arbitrary Wilson loop operator in Chern-Simons theory. Wilson loop operators in Chern-Simons theory can be given a description in terms of a configuration of branes or alternatively anti-branes in the resolved conifold geometry. The representation of the Wilson loop is encoded in the holonomy of the gauge field living on the dual brane configuration. By letting the branes undergo a new type of geometric transition, we argue that each Wilson loop operator can also be described by a bubbling Calabi-Yau geometry, whose topology encodes the representation of the Wilson loop. These Calabi-Yau manifolds provide a novel representation of knot invariants. For the unknot we confirm these identifications to all orders in the genus expansion.
Quantum Entanglement of Baby Universes
Mina Aganagic,Takuya Okuda,Hirosi Ooguri
Physics , 2006, DOI: 10.1016/j.nuclphysb.2007.04.006
Abstract: We study quantum entanglements of baby universes which appear in non-perturbative corrections to the OSV formula for the entropy of extremal black holes in Type IIA string theory compactified on the local Calabi-Yau manifold defined as a rank 2 vector bundle over an arbitrary genus G Riemann surface. This generalizes the result for G=1 in hep-th/0504221. Non-perturbative terms can be organized into a sum over contributions from baby universes, and the total wave-function is their coherent superposition in the third quantized Hilbert space. We find that half of the universes preserve one set of supercharges while the other half preserve a different set, making the total universe stable but non-BPS. The parent universe generates baby universes by brane/anti-brane pair creation, and baby universes are correlated by conservation of non-normalizable D-brane charges under the process. There are no other source of entanglement of baby universes, and all possible states are superposed with the equal weight.
Loop operators and S-duality from curves on Riemann surfaces
Nadav Drukker,David R. Morrison,Takuya Okuda
Mathematics , 2009, DOI: 10.1088/1126-6708/2009/09/031
Abstract: We study Wilson-'t Hooft loop operators in a class of N=2 superconformal field theories recently introduced by Gaiotto. In the case that the gauge group is a product of SU(2) groups, we classify all possible loop operators in terms of their electric and magnetic charges subject to the Dirac quantization condition. We then show that this precisely matches Dehn's classification of homotopy classes of non-self-intersecting curves on an associated Riemann surface--the same surface which characterizes the gauge theory. Our analysis provides an explicit prediction for the action of S-duality on loop operators in these theories which we check against the known duality transformation in several examples.
Scheme dependence of instanton counting in ALE spaces
Yuto Ito,Kazunobu Maruyoshi,Takuya Okuda
Mathematics , 2013, DOI: 10.1007/JHEP05(2013)045
Abstract: There have been two distinct schemes studied in the literature for instanton counting in A_{p-1} asymptotically locally Euclidean (ALE) spaces. We point out that the two schemes---namely the counting of orbifolded instantons and instanton counting in the resolved space---lead in general to different results for partition functions. We illustrate this observation in the case of N=2 U(N) gauge theory with 2N flavors on the A_{p-1} ALE space. We propose simple relations between the instanton partition functions given by the two schemes and test them by explicit calculations.
Quantum 't Hooft operators and S-duality in N=4 super Yang-Mills
Jaume Gomis,Takuya Okuda,Diego Trancanelli
Mathematics , 2009,
Abstract: We provide a quantum path integral definition of an 't Hooft loop operator, which inserts a pointlike monopole in a four dimensional gauge theory. We explicitly compute the expectation value of the circular 't Hooft operators in N=4 super Yang-Mills with arbitrary gauge group G up to next to leading order in perturbation theory. We also compute in the strong coupling expansion the expectation value of the circular Wilson loop operators. The result of the computation of an 't Hooft loop operator in the weak coupling expansion exactly reproduces the strong coupling result of the conjectured dual Wilson loop operator under the action of S-duality. This paper demonstrates - for the first time - that correlation functions in N=4 super Yang-Mills admit the action of S-duality.
Phenomenological constraints on universal extra dimensions at LHC and electroweak precision test
Kakuda, Takuya;Nishiwaki, Kenji;Oda, Kin-ya;Okuda, Naoya;Watanabe, Ryoutaro
High Energy Physics - Phenomenology , 2013,
Abstract: We show two types of bounds on five- and six-demensional universal extra dimension (UED) models from the latest results of the Higgs search at the LHC and of the electroweak precision data for the S and T parameters. The UED models on which we put lower bounds are the minimal UED model in five dimensions and the six dimensional ones. The highest possible ultraviolet cutoff scale for each UED model is evaluated from the vacuum stability of the Higgs potential by solving the renormalization group equation of the Higgs self coupling. The bounds on the KK scale in the minimal UED model is 650 GeV from the LHC results and 700 GeV from the S, T analysis at the 95% confidence level, while those in the several 6D UED models are from 850 GeV to 1350 GeV (Higgs search) and from 900 GeV to 1500 GeV (S,T analysis).
Higgs at ILC in Universal Extra Dimensions in Light of Recent LHC Data
Takuya Kakuda,Kenji Nishiwaki,Kin-ya Oda,Naoya Okuda,Ryoutaro Watanabe
Physics , 2012,
Abstract: We present bounds on all the known universal extra dimension models from the latest Higgs search data at the Large Hadron Collider, taking into account the Kaluza-Klein (KK) loop effects on the dominant gluon-fusion production and on the diphoton/digluon decay. The lower bound on the KK scale is from 500GeV to 1TeV depending on the model. We find that the Higgs production cross section with subsequent diphoton decay can be enhanced by a factor 1.5 within this experimental bound, with little dependence on the Higgs mass in between 115GeV and 130GeV. We also show that in such a case the Higgs decay branching ratio into a diphoton final state can be suppressed by a factor 80%, which is marginally observable at a high energy/luminosity option at the International Linear Collider. The Higgs production cross section at a photon-photon collider can also be suppressed by a similar factor 90%, being well within the expected experimental reach.
Phase-Field Modeling for the Three-Dimensional Space-Filling Structure of Metal Foam Materials  [PDF]
Takuya Uehara
Open Journal of Modelling and Simulation (OJMSi) , 2015, DOI: 10.4236/ojmsi.2015.33013
Abstract: Phase-field modeling for three-dimensional foam structures is presented. The foam structure, which is generally applicable for porous material design, is geometrically approximated with a space-filling structure, and hence, the analysis of the space-filling structure was performed using the phase field model. An additional term was introduced to the conventional multi-phase field model to satisfy the volume constraint condition. Then, the equations were numerically solved using the finite difference method, and simulations were carried out for several nuclei settings. First, the nuclei were set on complete lattice points for a bcc or fcc arrangement, with a truncated hexagonal structure, which is known as a Kelvin cell, or a rhombic dodecahedron being obtained, respectively. Then, an irregularity was introduced in the initial nuclei arrangement. The results revealed that the truncated hexagonal structure was stable against a slight irregularity, whereas the rhombic polyhedral was destroyed by the instability. Finally, the nuclei were placed randomly, and the relaxation process of a certain cell was traced with the result that every cell leads to a convex polyhedron shape.
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