arXiv subjects

Nobuyoshi Ohta

Publications and source records attributed to Nobuyoshi Ohta.

At least 127 records · Page 7Linked to original sources

arXiv2002

Introduction to branes and M-theory for relativists and cosmologists

We review the recent developments in superstrings. We start with a brief summary of various consistent superstring theories and discuss T-duality which necessarily leads to the presence of D-branes. The properties of D-branes are summarized and we discuss how these suggest the existence of 11-dimensional quantum theory, M-theory, which is believed to give rise to various superstrings as perturbative expansions around particular backgrounds in the theory. We also discuss the interpretation of brane solutions as black holes in string theories and statistical explanation of Bekenstein-Hawking entropy. The idea behind this interpretation is that there is a fundamental duality between closed (gravity) and open (gauge theory) string degrees of freedom, one of whose manifestation is what is kown as AdS/CFT correspondence. The idea is used to discuss the greybody factors for BTZ black holes. Finally the entropy of various balck holes are discussed in connection with Cardy-Verlinde formula.

gr-qc↗

arXiv2002

Supertubes and Supercurves from M-Ribbons

We construct 1/4 BPS configurations, `M-ribbons', in M-theory on T^2, which give the supertubes and supercurves in type IIA theory upon dimensional reduction. These M-ribbons are generalized so as to be consistent with the SL(2,Z) modular transformation on T^2. In terms of the type IIB theory, the generalized M-ribbons are interpreted as an SL(2,Z) duality family of super D-helix. It is also shown that the BPS M-ribbons must be straight in one direction.

hep-th↗

arXiv2002

Moduli Space and Scattering of D0-Branes in Noncommutative Super Yang-Mills Theory

We study the moduli space of the D0-brane system on Dp-branes realized in the noncommutative super Yang-Mills theory. By examining the fluctuations around the solitonic solutions generated by solution generating technique, we confirm the interpretation of the moduli as the positions of D0-branes on Dp-branes. Low-energy scattering process is also examined for two D0-branes. We find that the D0-branes scatter at right angle for head-on collision in the D0-D4 system. For D0-D6 and D0-D8 systems we find special solutions which reduce to the D0-D4 case, giving the same behavior. This suggests that the scattering at right angle for head-on collision is a universal behavior of this kind of soliton scatterings.

hep-th↗

arXiv2001

Supersymmetric D2 anti-D2 Strings

We consider the flat supersymmetric D2 and anti-D2 system, which follows from ordinary noncommutative D2 anti-D2 branes by turning on an appropriate worldvolume electric field describing dissolved fundamental strings. We study the strings stretched between D2 and anti-D2 branes and show explicitly that the would-be tachyonic states become massless. We compute the string spectrum and clarify the induced noncommutativity on the worldvolume. The results are compared with the matrix theory description of the worldvolume gauge theories.

hep-th↗

arXiv2001

Supersymmetry, Spectrum and Fate of D0-Dp Systems with B-field

It has been shown that D0-D$p$ $(p=2, 4, 6, 8)$ systems can be BPS in the presence of $B$-field even if they are not otherwise. We review the number of remaining supersymmetries, the open string ground state spectrum and the construction of the D0-D$p$ systems as solitonic solutions in the noncommutative super Yang-Mills theory. We derive the complete mass spectrum of the fluctuations to discuss the stability of the systems. The results are found to agree with the analysis in the string picture. In particular, we show that supersymmetry is enhanced in D0-D8 depending on the $B$-fields and it is consistent with the degeneracy of mass spectrum. We also derive potentials and discuss their implications for these systems.

hep-th↗

arXiv2001

Bekenstein Bound, Holography and Brane Cosmology in Charged Black Hole Backgrounds

We obtain a Bekenstein entropy bound for the charged objects in arbitrary dimensions ($D\ge 4$) using the D-bound recently proposed by Bousso. With the help of thermodynamics of CFTs corresponding to AdS Reissner-Norström (RN) black holes, we discuss the relation between the Bekenstein and Bekenstein-Verlinde bounds. In particular we propose a Bekenstein-Verlinde-like bound for the charged systems. In the Einstein-Maxwell theory with a negative cosmological constant, we discuss the brane cosmology with positive tension using the Binetruy-Deffayet-Langlois approach. The resulting Friedman-Robertson-Walker equation can be identified with the one obtained by the moving domain wall approach in the AdS RN black hole background. Finally we also address the holographic property of the brane universe.

hep-th↗

arXiv2000

Noncommutative Gauge Dynamics from Brane Configurations with Background B field

We study D=3 field theories on the D3-branes stretched between two NS5-branes with NS B-field background. The theory is a noncommutative gauge theory. The mirror symmetry and S-duality of the theory are discussed. A new feature is that the mirror of the noncommutative gauge theory is not a field theory but an open string decoupled from the closed string. We also consider brane creation phenomena and use the result to discuss the analogue of the Seiberg duality. A noncommutative soliton is interpreted as a D1-brane induced on D3-brane.

hep-th↗

arXiv2000

Lorentz Transformation and Light-Like Noncommutative SYM

We show that combining the spatial noncommutative SYM limit and Lorentz transformation, one can obtain a well-behaved light-like noncommutative SYM limit. The light-like noncommutative SYM is unitary. When the boost velocity is finite, the resulting theory with space-time noncommutativity is unitary as well. The light-like noncommutative SYM limit can also be approached by combining the noncommutative open string theory limit and Lorentz transformation. Along this line, we obtain the supergravity dual for the light-like noncommutative SYM, which is the same as the one acquired using a different method. As a comparison, the supergravity duals for the ordinary SYM, spatial noncommutative SYM and the noncommutative open string theories are given as well, in an infinitely-boosted frame with finite momentum density, which are the decoupling limits of bound states (Dp, W), (D($p-2$), W, Dp), and (F1, W, Dp), respectively.

hep-th↗

arXiv2000

(F1, D1, D3) Bound State, Its Scaling Limits and SL(2,Z) Duality

We discuss the properties of the bound state (F1, D1, D3) in IIB supergravity in three different scaling limits and the $SL(2,{\bf Z})$ transformation of the resulting theories. In the simple decoupling limit with finite electric and magnetic components of NS $B$ field, the worldvolume theory is the ${\cal N}$=4 super Yang-Mills (SYM) and the supergravity dual is still the $AdS_5 \times S^5$. In the large magnetic field limit with finite electric field, the theory is the noncommutative super Yang-Mills (NCSYM), and the supergravity dual is the same as that without the electric background. We show how to take the decoupling limit of the closed string for the critical electric background and finite magnetic field, and that the resulting theory is the noncommutative open string (NCOS) with both space-time and space-space noncommutativities. It is shown that under the $SL(2, {\bf Z})$ transformation, the SYM becomes itself with a different coupling constant, the NCSYM is mapped to a NCOS, and the NCOS in general transforms into another NCOS and reduces to a NCSYM in a special case.

hep-th↗

arXiv2000

Noncommutative and Ordinary Super Yang-Mills on (D$(p-2)$, D$p$) Bound States

We study properties of (D$(p-2)$, D$p$) nonthreshold bound states ($2 \le p \le 6 $) in the dual gravity description. These bound states can be viewed as D$p$-branes with a nonzero NS $B$ field of rank two. We find that in the decoupling limit, the thermodynamics of the $N_p$ coincident D$p$-branes with $B$ field is the same not only as that of $N_p$ coincident D$p$-branes without $B$ field, but also as that of the $N_{p-2}$ coincident D$(p-2)$-branes with two smeared coordinates and no $B$ field, for $N_{p-2}/N_p= \tilde{V}_2/[(2π)^2 \tilde{b}]$ with $\tilde{V}_2$ being the area of the two smeared directions and $\tilde{b}$ a noncommutativity parameter. We also obtain the same relation from the thermodynamics and dynamics by probe methods. This suggests that the noncommutative super Yang-Mills with gauge group $U(N_p)$ in ($p+1$) dimensions is equivalent to an ordinary one with gauge group $U(\infty)$ in ($p-1$) dimensions in the limit $\tilde{V}_2 \to \infty$. We also find that the free energy of a D$p$-brane probe with $B$ field in the background of D$p$-branes with $B$ field coincides with that of a D$p$-brane probe in the background of D$p$-branes without $B$ field.

hep-th↗

arXiv2000

On the Thermodynamics of Large N Noncommutative Super Yang-Mills Theory

We study the thermodynamics of the large N noncommutative super Yang-Mills theory in the strong 't Hooft coupling limit in the spirit of AdS/CFT correspondence. It has already been noticed that some thermodynamic quantities of near-extremal D3-branes with NS B fields, which are dual gravity configurations of the noncommutative ${\cal N}$=4 super Yang-Mills theory, are the same as those without B fields. In this paper, (1) we examine the $α'^3 R^4$ corrections to the free energy and find that the part of the tree-level contribution remains unchanged, but the one-loop and the non-perturbative D-instanton corrections are suppressed, compared to the ordinary case. (2) We consider the thermodynamics of a bound state probe consisting of D3-branes and D-strings in the near-extremal D3-brane background with B field, and find the thermodynamics of the probe is the same as that of a D3-brane probe in the D3-brane background without B field. (3) The stress-energy tensor of the noncommutative super Yang-Mills theory is calculated via the AdS/CFT correspondence. It is found that the tensor is not isotropic and its trace does not vanish, which confirms that the super Yang-Mills is not conformal even in four dimensions due to the noncommutative nature of space. Our results render further evidence for the argument that the large N noncommutative and ordinary super Yang-Mills theories are equivalent not only in the weak coupling limit, but also in the strong coupling limit.

hep-th↗

arXiv1999

Spectrum of Maxwell-Chern-Simons Theory Realized on Type IIB Brane

We study the 3D field theory on one D3-brane stretched between (r,s) and (p,q)5-branes. The boundary conditions are determined from the analysis of NS5 and D5 charges of the two 5-branes. We carry out the mode expansions for all the fields and identify the field theory as Maxwell-Chern-Simons theory. We examine the mass spectrum to determine the conditions for unbroken supersymmetry (SUSY) in this field theory and compare the results with those from the brane configurations. The spectrum is found to be invariant under the Type IIB SL(2,{\bf Z})-transformation. We also discuss the theory with matters and its S-dual configuration. The result suggests that the equivalence under S-duality may be valid if we include all the higher modes in the theories with matters. We also find an interesting phenomenon that SUSY enhancement happens in the field theory after dimensional reduction from 3D to 2D.

hep-th↗

arXiv1999

Surface counterterms and boundary stress-energy tensors for asymptotically non-anti-de Sitter spaces

For spaces which are not asymptotically anti-de Sitter where the asymptotic behavior is deformed by replacing the cosmological constant by a dilaton scalar potential, we show that it is possible to have well-defined boundary stress-energy tensors and finite Euclidean actions by adding appropriate surface counterterms. We illustrate the method by the examples of domain-wall black holes in gauged supergravities, three-dimensional dilaton black holes and topological dilaton black holes in four dimensions. We calculate the boundary stress-energy tensor and Euclidean action of these black configurations and discuss their thermodynamics. We find new features of topological black hole thermodynamics.

hep-th↗

arXiv1999

Maxwell Chern-Simons Solitons from Type IIB String Theory

We study various three-dimensional supersymmetric Maxwell Chern-Simons solitons by using type IIB brane configurations. We give a systematic classification of soliton spectra such as topological BPS vortices and nontopological vortices in $\mathcal{N}=2,3$ supersymmetric Maxwell Chern-Simons system via the branes of type IIB string theory. We identify the brane configurations with the soliton spectra of the field theory and obtain a nice agreement with field theory aspects. We also discuss possible brane constructions for BPS domain wall solutions.

hep-th↗

arXiv1999

Spacetime Superalgebra in AdS_4 \times S^7 via Supermembrane Probe

The spacetime superalgebra via the supermembrane probe in the background of AdS_4 \times S^7 is discussed to the lowest order in the spinor coordinate $\t$. To obtain the correct spacetime superalgebras, all $\t^2$ order corrections for supervielbein and super 3-form gauge potential have to be included. The central extension of the superalgebra OSp(8|4) of the super isometries for AdS_4 \times S^7 is found.

hep-th↗

arXiv1999

Three-Dimensional Gauge Dynamics from Brane Configurations with (p,q)-Fivebrane

We study three-dimensional gauge dynamics by using type IIB superstring brane configurations, which can be obtained from the M-theory configuration of M2-branes stretched between two M5-branes with relative angles. Our construction of brane configurations includes (p,q)5-brane and gives a systematic classification of possible three-dimensional gauge theories. The explicit identification of gauge theories are made and their mirror symmetry is discussed. As a new feature, our theories include interesting Maxwell-Chern-Simons system whose vacuum structure is also examined in detail, obtaining results consistent with the brane picture.

hep-th↗

arXiv1999

Non-Extreme Black Holes from Intersecting M-Branes

We investigate the possibility of extending non-extreme black hole solutions made of intersecting M-branes to those with two non-extreme deformation parameters, similar to Reissner-Nordstrøm solutions. General analysis of possible solutions is carried out to reduce the problem of solving field equations to a simple algebraic one for static spherically-symmetric case in $D$ dimensions. The results are used to show that the extension to two-parameter solutions is possible for $D=4,5$ dimensions but not for higher dimensions, and that the area of horizon always vanishes in the extreme limit for black hole solutions for $D \geq 6$ except for two very special cases which are identified. Various solutions are also summarized.

hep-th↗

arXiv1998

Thermalization of Poincaré Vacuum State and Fermion Emission from AdS_3 Black Holes in Bulk-Boundary Correspondence

The greybody factors for spin 1/2 particles in the BTZ black holes are discussed from 2D CFT in bulk-boundary correspondence. It is found that the initial state of spin 1/2 particle in the BTZ black holes can be described by the Poincaré vacuum state in boundary 2D CFT, and the nonlinear coordinate transformation causes the thermalization of the Poincaré vacuum state. For special case, our results for the greybody factors agree with the semiclassical calculation.

hep-th↗