arXiv subjects

Hiroshi Kunitomo

Publications and source records attributed to Hiroshi Kunitomo.

29 records · Page 2Linked to original sources

arXiv2007

Lower-dimensional superstrings in the double-spinor formalism

We study lower-dimensional superstrings in the double-spinor formalism introduced by Aisaka and Kazama. These superstrings can be consistently quantized and are equivalent to the lower-dimensional pure-spinor superstrings proposed by Grassi and Wyllard. The unexpected physical spectrum of the pure-spinor superstrings may thus be regarded as a manifestation of noncriticality. We also discuss how to couple these covariant superstrings to the compactified degrees of freedom described by the N=2 superconformal field theory.

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arXiv2006

One-Loop Amplitudes in Supersymmetric QCD from MHV Vertices

The Cachazo-Svrcek-Witten (CSW) rule for efficiently calculating gauge theory amplitudes is extended to N=1 supersymmetric QCD (SQCD), incorporating massless quarks, in a way preserving the manifest supersymmetry. Using this extended CSW rule, we obtain compact expressions of all the one-loop MHV amplitudes in SQCD including one or two external quark-antiquark (chiral-antichiral multiplets) pairs. The collinear sigularities of the five point amplitudes are investigated to confirm the consistency of the results.

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arXiv2004

Hybrid Superstring on AdS_3 and Space-Time Superconformal Symmetry

Using a hybrid formalism, superstrings on AdS(3) x S(1) are studied in a manifestly supersymmetric manner. The world-sheet fields in this description including superspace coordinates are obtained through a field redefinition from the corresponding ones in the RNS formalism. The physical states are defined with the BRST cohomology as an N=4 topological string theory. The physical spectra for some lower mass levels are investigated. We identify two series of the space-time chiral primaries which have already been obtained from the analysis in the RNS formalism. We find that they are described by the chiral and the vector supermultiplets, but the on-shell physical structure of the latter depends on whether it is massive or massless. The spece-time supersymmetry on this background is extended to the boundary N=2 uperconformal symmetry. We explicitly construct its generators and study how they act on specific supermultiplets.

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arXiv2003

Correlation between momentum modes and winding modes in Brandenberger-Vafa's string cosmological model

Brandenberger and Vafa have proposed the string cosmological model based on T-duality. In this model, they took the toroidal target space and introduced the new position \tilde{x} conjugate to the winding mode, in addition to the position x conjugate to the momentum mode. In this way they can describe a universe larger than the string scale with the coordinate x and one smaller with the coordinate \tilde{x}. Resultingly, they never encounter the singularity seen in the standard Big Bang scenario. The most interesting phenomenon in this model is the transition from \tilde{x}-space to x-space when the size of universe is nearly the string scale. Here, we define the dispersion of the momentum number m times the winding number w as the `correlation' of momentum modes and winding modes. Then using the statistical mechanics of strings on a torus, we calculate the correlation in low and high temperature limits, and we consider the possibility that we can observe this effect today, but we will see that this is unlikely.

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arXiv2003

Hybrid Superstrings in NS-NS Plane Waves

By using the hybrid formalism, superstrings in four-dimensional NS-NS plane waves are studied in a manifest supersymmetric manner. This description of the superstring is obtained by a field redefinition of the RNS worldsheet fields and defined as a topological N=4 string theory. The Hilbert space consists of two types of representations describing short and long strings. We study the physical spectrum to find boson-fermion asymmetry in the massless spectrum of the short string. Some massive spectrum of the short string and the massless spectrum of the long string are also studied.

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arXiv2002

Hybrid Superstrings on Singular Calabi-Yau Fourfolds

Two-dimensional hybrid superstring on singular Calabi-Yau manifolds is studied by the field redefinition of the NSR formalism. The compactification on singular Calabi-Yau fourfold is described by N=2 super-Liouville theory and N=2 Landau-Ginzburg models. We examine the world-sheet topological N=4 superconformal algebra, which is useful to identify physical states of the theory. It is shown that the space-time superconformal symmetry is not compatible with this original topological algebra. A new model is proposed by modifying the topological superconformal generators, which is consistent with space-time N=2 superconformal symmetry.

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arXiv1996

Topological Field Theory and Second-Quantized Five-Branes

We construct the six-dimensional topological field theory appropriate to describe the ground-state configurations of D5-branes. A close examination on the degenerations of D5-branes gives us the physical observables which can be regarded as the Poincaré duals of the cycles of the moduli space. These observables are identified with the creation opeartors of the bound states of D5-branes and lead to the second quantization of five-branes. This identification of the bound states with the cycles also provides their topological stability and suggests that the bound states of five-branes have internal structures. The partition function of the second-quantized five-branes is also discussed.

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arXiv1994

A Hierarchy of Super $w$\ Strings

It is shown that the N-extended super $w_n$\ string can be obtained as a special class of vacua of both the N-extended super $w_{n+1}$\ string and the (N+1)-extended super $w_n$\ string. This hierarchy of super $w$\ string theories includes as subhierarchies both the superstring hierarchy given by Bastianelli, Ohta and Petersen and the $w$\ string hierarchy given by the authors.

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arXiv1994

On the Nonlinear Realization of the Superconformal Symmetry

The nonlinear realization of the superconformal symmetry in two dimensions is considered. The superconformal symmetry is realized by means of dimension $-1/2$\ Nambu-Goldstone fermion $ξ$\ and its dimension 3/2 conjugate $η$. A matter coupling of these Nambu- Goldstone fermions reproduce the realization found by Berkovits and Vafa to show the equivalence between the bosonic string and a $N=1$\ superstring. This indicates that this equivalence is a result of the super Higgs mechanism as a two dimensional field theory, in which the NG fermions become unphysical.

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arXiv1994

A Universal w String Theory

It has been shown that there is a sequential embedding structure in a $w_N$\ string theory based on a linearized $W_N$\ algebra. The $w_N$\ string theory is obtained as a special realization of the $w_{N+1}$\ string. The $w_{\infty}$\ string theory is a universal string theory in this sense. We have also shown that there is a similar sequence for $N=1$\ string theory. The $N=1\ w_N$\ string can be given as a special case of the $N=1\ w_{N+1}$\ string. In addition, we show that the $w_3$\ string theory is obtained as a special realization of the $N=1\ w_3$\ string. We conjecture that the $w_N$\ string can be obtained as a special $N=1\ w_N$\ string for general $w_N$. If this is the case, $N=1\ w_{\infty}$\ string theory is more universal since it includes both $N=0$\ and $N=1$\ $w_N$\ string theories.

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arXiv1993

BRST Analysis of Physical States in Two-Dimensional Black Hole

We study the BRST cohomology for $SL(2,R)/U(1)$ coset model, which describes an exact string black hole solution. It is shown that the physical spectrum could contain not only the extra discrete states corresponding to those in $c=1$ two-dimensional gravity but also many additional new states with ghost number $N_{FP}= -1 \sim 2$. We also discuss characters for nonunitary representations and the relation of our results to other approaches.

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