Masafumi Ishihara

Multiquark baryons and color screening at finite temperature

We study baryons in SU(N) gauge theories at finite temperature according to the gauge/string correspondence based on IIB string theory. The baryon is constructed out of the D5-brane and N fundamental strings to form a color singlet N-quark bound state. At finite temperature and in the deconfining phase, we could find k(<N)-quark baryons. Thermal properties of such k-quark baryons and also of the N-quark baryon are examined. We study the temperature dependence of color screening distance and the Debye length of the baryon of the k quark and the N quark. We also estimate the melting temperature, where the baryons decay into quarks and gluons completely.

Gauge theory in de Sitter space-time from a holographic model

Yang-Mills (YM) theory with flavor quarks in the dS{sub 4} is studied through the dual supergravity in the AdS{sub 5}xS{sup 5} background with nontrivial dilaton and axion. The flavor quarks are introduced by embedding a probe D7 brane. We find that the dynamical properties of YM theory in the dS{sub 4} are similar to the case of the finite temperature theory given by the 5d AdS-Schwarzschild background. In the case of dS{sub 4}, however, contrary to the finite temperature case, the gauge-field condensate plays an important role on the dynamical properties of quarks. We also give the quark-antiquark potential and meson spectra to find possible quark-bound states. We arrive at the conclusion that, while the quarks are not confined in the dS{sub 4}, we could find stable meson states at very small cosmological constant as expected in the present universe. However, there would be no hadrons at early universe as in the inflation era.

Flavor quarks in AdS4 and gauge/gravity correspondence

The non-perturbative properties of the gauge theories in the AdS

Holographic confining gauge theory and response to the electric field

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Baryonium in confining gauge theories

are studied in the dual supergravity by including light flavor quarks, which are introduced by a D7 brane embedding. Contrary to the cases of Minkowski and dS

Glueball instability and thermalization driven by dark radiation

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D3/D7 holographic gauge theory and chemical potential

, the dilaton does not play any important dynamical role in the AdS

Baryons with D 5 -brane vertex and k -quark states

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Baryons withD5-brane vertex andk-quark states

case, and the characteristic properties like the quark confinement and the chiral symmetry breaking are realized mainly due to the geometry AdS

Flavor quarks in AdS{sub 4} and gauge/gravity correspondence

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