Supersphere

The spherical D2-brane solution is obtained without RR external background. The solution is shown to preserve $(1/4)$ supersymmetries. The configurations obtained depend on the integration constant $R_0$. For $R_0 \neq 0$ the shape of the solution is a deformed sphere. When, however, $R_0 = 0$, the D2-brane system seems to exhibit a brane-anti-brane configuration.Comment: 11 pages, 2 figure

General Criterion for the existence of Supertube and BIon in Curved Target Space

The supertube and BIon spike solutions are examined in a general curved target space. The criteria for the existence of these solutions are explicitly derived. Also the equation which the general BIon solution should satisfy is derived.Comment: 12 pages, no figur

D2-branes with magnetic flux in the presence of RR fields

D2-branes are studied in the context of Born-Infeld theory as a source of the 3-form RR gauge potential. Considering the static case with only a radial magnetic field it is shown that a locally stable hemispherical deformation of the brane exists which minimises the energy locally. Since the D2-brane carries also the charge of D0-branes, and the RR spacetime potential is unbounded from below, these can tunnel to condense on the D2-brane. The corresponding instanton-like configuration and the tunneling rate are derived and discussed.Comment: 24 pages, 1 figure included, version to appear in NP

Assessment and Optimization of Medical Risks using the Integrated Medical Model

ObjectiveDevelop an evidence-based, probabilistic risk forecasting model that can help guide mission planning, requirements development, and align science with engineering technology development

Fuzzy BIon

We construct a solution of the BFSS matrix theory, which is a counterpart of the BIon solution representing a fundamental string ending on a bound state of a D2-brane and D0-branes. We call this solution the `fuzzy BIon' and show that this configuration preserves 1/4 supersymmetry of type IIA superstring theory. We also construct an effective action for the fuzzy BIon by analyzing the nonabelian Born-Infeld action for D0-branes. When we take the continuous limit, with some conditions, this action coincides with the effective action for the BIon configuration.Comment: 11 pages, 1 figure, reference and note adde

Condition for Superradiance in Higher-dimensional Rotating Black Holes

It is shown that the superradiance modes always exist in the radiation by the $(4+n)$-dimensional rotating black holes. Using a Bekenstein argument the condition for the superradiance modes is shown to be $0 < \omega < m \Omega$ for the scalar, electromagnetic and gravitational waves when the spacetime background has a single angular momentum parameter about an axis on the brane, where $\Omega$ is a rotational frequency of the black hole and $m$ is an azimuthal quantum number of the radiated wave.Comment: 8 pages, no figure, v2: references added, version to appear in PL

Proof of universality for the absorption of massive scalars by the higher-dimensional Reissner-Nordstr\"{o}m black holes

Motivated by black hole experiments as a consequence of the TeV-scale gravity arising from modern brane-world scenarios, we study the absorption problem for the massive scalars when the spacetime background is a $(4+n)$-dimensional Reissner-Nordstr\"{o}m black hole. For analytic computation we adopt the near-extreme condition in the spacetime background. It is shown that the low-energy absorption cross section for the s-wave case holds an universality, {\it i.e.} the absorption cross section equals to the area of the black hole horizon divided by a velocity parameter.Comment: 11 pages, no figure, V2: version to appear in PL

Condition for the Superradiance Modes in Higher-Dimensional Rotating Black Holes with Multiple Angular Momentum Parameters

The condition for the existence of the superradiance modes is derived for the incident scalar, electromagnetic and gravitational waves when the spacetime background is a higher-dimensional rotating black hole with multiple angular momentum parameters. The final expression of the condition is $0 < \omega < \sum_i m_i \Omega_i$, where $\Omega_i$ is an angular frequency of the black hole and, $\omega$ and $m_i$ are the energy of the incident wave and the $i$-th azimuthal quantum number. The physical implication of this condition in the context of the brane-world scenarios is discussed.Comment: 11 pages, no figur

Ratio of absorption cross section for Dirac fermion to that for scalar in the higher-dimensional black hole background

The ratio of the low-energy absorption cross section for Dirac fermion to that for minimally coupled scalar is computed when the spacetimes are various types of the higher-dimensional Reissner-Nordstr\"{o}m black holes. It is found that the low-energy absorption cross sections for the Dirac fermion always goes to zero in the extremal limit regardless of the detailed geometry of the spacetime. The physical importance of our results is discussed in the context of the brane-world scenarios and string theories.Comment: 12 pages, no figure, V2: several references added, version to appear in PL

Asymptotic Quasinormal Frequencies of Brane-Localized Black Hole

The asymptotic quasinormal frequencies of the brane-localized $(4+n)$-dimensional black hole are computed. Since the induced metric on the brane is not an exact vacuum solution of the Einstein equation defined on the brane, the real parts of the quasinormal frequencies $\omega$ do not approach to the well-known value $T_H \ln 3$ but approach to $T_H \ln k_n$, where $k_n$ is a number dependent on the extra dimensions. For the scalar perturbation $Re(\omega / T_H) = \ln 3$ is reproduced when $n = 0$. For $n \neq 0$, however, $Re(\omega / T_H)$ is smaller than $\ln 3$. It is shown also that when $n > 4$, $Im(\omega / T_H)$ vanishes in the scalar perturbation. For the gravitational perturbation it is shown that $Re(\omega / T_H) = \ln 3$ is reproduced when $n = 0$ and $n = 4$. For different $n$, however, $Re(\omega / T_H)$ is smaller than $\ln 3$. When $n = \infty$, for example, $Re(\omega / T_H)$ approaches to $\ln (1 + 2 \cos \sqrt{5} \pi) \approx 0.906$. Unlike the scalar perturbation $Im(\omega / T_H)$ does not vanish regradless of the number of extra dimensions.Comment: 15 pages, 1 eps figure: V2 one more reference added. The derivtaion of the effective potential is explained in detail. Version of PL