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Kin-ya Oda

Publications and source records attributed to Kin-ya Oda.

89 records · Page 5Linked to original sources

Geometric cross sections of rotating strings and black holes

We study the production cross section of a highly excited string with fixed angular momentum from an ultra-high energy collision of two light strings. We find that the cross section exhibits geometric behavior in a certain region of angular-momentum/impact-parameter space. This geometric behavior is common to the differential cross sections of a black hole production with fixed angular momentum and thus we see another correspondence between strings and black holes.

hep-th

Dynamical Rearrangement of Theta Parameter in Presence of Mixed Chern-Simons Term

We study the five-dimensional SU(3)_c x U(1)_C gauge theory on the orbifold S^1/Z_2 with a mixed Chern-Simons term. We particularly pay attention to the realization of the dynamical rearrangement of the theta parameter for SU(3)_c. It is shown that the physics remains invariant under a large gauge transformation which even changes the action, completely removing the theta parameter, because of the Hosotani mechanism for the U(1)_C gauge interactions. In other words, we show that the theta parameter can be regarded as a boundary condition for the orbifolding in light of the dynamical rearrangement.

hep-ph

A Holographic Dual of Bjorken Flow

We propose a consistent setup for a holographic dual of Bjorken flow of strongly coupled large-Nc N=4 SYM-theory plasma. We employ Eddington-Finkelstein type coordinates for the dual geometry, and we propose a late-time expansion there. We construct the dual geometry order by order, and we show that the transport coefficients are determined by the regularity of the geometry. We also show that the dual geometry has an apparent horizon hence an event horizon, which covers the singularity at the origin. We prove that the dual geometry is regular at all orders under an appropriate choice of the transport coefficients. Our model is a concrete well-defined example of time-dependent AdS/CFT.

hep-th

Effects of brane-flux transition on black holes in string theory

Extremal N=2 black holes in four dimensions can be described by an ensemble of D3-branes wrapped on internal supersymmetric three-cycles of Calabi-Yau threefolds on which type IIB superstring theory is compactified. We construct a similar configuration, with extra RR and NS-NS three-form fluxes being turned on. We can avoid the Freed-Witten anomaly on the D3-branes by enforcing the pullback of these extra fluxes to the D3-branes to vanish at the classical level. In the setup the D3-brane charge is not conserved since it is classified as a trivial class in twisted K-theory. Consequently, the D3-branes may disappear by encountering an instantonic D5-brane localized in time. We discuss what happens on the black hole described by such disappearing D3-branes, relying mainly on topological arguments. Especially, we argue that another RR three-form flux will be left as a lump of remnant which is localized in the uncompactified four-dimensional space-time and that it may carry the same amount of degrees of freedom to describe a black hole, in cooperation with the original NS-NS flux, after this transition of the D3-branes.

hep-th

Orbifold Family Unification

We study the possibility of complete family unification in higher-dimensional space-time. Three families of matters in SU(5) grand unified theory are derived from a single bulk multiplet of SU(N) gauge group (N >= 9) in the framework of S^1/Z_2 orbifold models. In the case of the direct orbifold breaking down to the standard model gauge group, there are models in which bulk fields from a single multiplet and a few brane fields compose three families of quarks and leptons.

hep-ph

QCD Effects in the Decays of TeV Black Holes

In models with ``large'' and/or warped extra dimensions, the higher-dimensional Planck scale may be as low as a TeV. In that case black holes with masses of a few TeV are expected to be produced copiously in multi-TeV collisions, in particular at the LHC. These black holes decay through Hawking radiation into typically O(20) Standard Model particles. Most of these particles would be strongly interacting. Naively this would lead to a final state containing 10 or so hadronic jets. However, it has been argued that the density of strongly interacting particles would be so large that they thermalize, forming a ``chromosphere'' rather than well-defined jets. In order to investigate this, we perform a QCD simulation which includes parton-parton scattering in addition to parton showering. We find the effects of parton scattering to remain small for all cases we studied, leading to the conclusion that the decays of black holes with masses within the reach of the LHC will not lead to the formation of chromospheres.

hep-ph

Rotating Black Holes at Future Colliders. III. Determination of Black Hole Evolution

TeV scale gravity scenario predicts that the black hole production dominates over all other interactions above the scale and that the Large Hadron Collider will be a black hole factory. Such higher dimensional black holes mainly decay into the standard model fields via the Hawking radiation whose spectrum can be computed from the greybody factor. Here we complete the series of our work by showing the greybody factors and the resultant spectra for the brane localized spinor and vector field emissions for arbitrary frequencies. Combining these results with the previous works, we determine the complete radiation spectra and the subsequent time evolution of the black hole. We find that, for a typical event, well more than half a black hole mass is emitted when the hole is still highly rotating, confirming our previous claim that it is important to take into account the angular momentum of black holes.

hep-th

Rotating black holes at future colliders II: Anisotropic scalar field emission

This is the sequel to the first paper of the series, where we have discussed the Hawking radiation from five-dimensional rotating black holes for spin 0, 1/2 and 1 brane fields in the low frequency regime. We consider the emission of a brane localized scalar field from rotating black holes in general space-time dimensions without relying on the low frequency expansions.

hep-th

Anisotropic scalar field emission from TeV scale black hole

Black holes are predicted to be copiously produced at the CERN Large Hadron Collider in the scenarios of TeV scale gravity. We report recent progress in studying decay of such a higher dimensional black hole in D=4+n dimensions through the Hawking radiation into brane localized fields taking into account its angular momentum which is indispensable for realistic simulations. Presented is the greybody factors for a scalar field emission, which confirms our previous results in low energy approximation: (i) the existence of super-radiance modes and (ii) the non-trivial angular distribution of radiated scalar field. Phenomenological implications and future plans are discussed.

hep-ph

Wilson Lines in Warped Space: Dynamical Symmetry Breaking and Restoration

The dynamics of Wilson lines integrated along a warped extra dimension has been unknown. We study a five dimensional SU(N) pure gauge theory with Randall-Sundrum warped compactification on S^1/Z_2. We clarify the notion of large gauge transformations that are non-periodic on the covering space for this setup. We obtain Kaluza-Klein expansions of gauge and ghost fields for the most general twists and background gauge field configurations, which break the gauge symmetry at classical level in general. We calculate the one-loop effective potential and find that the symmetry corresponding to the subgroup allowing continuous Wilson lines is dynamically restored. The presented method can be directly applied to include extra fields. The connection to dynamical Scherk-Schwarz supersymmetry breaking in warped space is discussed.

hep-ph

Rotating Black Holes at Future Colliders

We consider the production and decay of TeV-scale black holes. Evaluation of the production cross section of higher dimensional rotating black holes is made. The master field equation for general spin-$s$ fields confined on brane world is derived. For five-dimensional (Randall-Sundrum) black holes, we obtain analytic formulae for the greybody factors in low frequency expansion.

hep-ph

Rotating Black Holes/Rings at Future Colliders

The hierarchy between the electroweak and Planck scales can be reduced when the extra dimensions are compactified with large volume or with warped geometry, resulting in the fundamental scale of the order of TeV. In such a scenario, one can experimentally study the physics above the Planck scale. We discuss black hole/ring production at future colliders.

hep-ph

Black Holes at future colliders

We consider the production and decay of TeV sized black holes. After discussing evaluation of the production cross section of higher dimensional rotating black holes and black rings, the master equation for general spin-$s$ fields confined on brane world is derived. For five-dimensional (Randall-Sundrum) black holes, we obtain analytic formulae for the greybody factors in low frequency expansion.

hep-ph

Rotating black holes at future colliders: Greybody factors for brane fields

We study theoretical aspects of the rotating black hole production and evaporation in the extra dimension scenarios with TeV scale gravity, within the mass range in which the higher dimensional Kerr solution provides good description. We evaluate the production cross section of black holes taking their angular momenta into account. We find that it becomes larger than the Schwarzschild radius squared, which is conventionally utilized in literature, and our result nicely agrees with the recent numerical study by Yoshino and Nambu within a few percent error for higher dimensional case. In the same approximation to obtain the above result, we find that the production cross section becomes larger for the black hole with larger angular momentum. Second, we derive the generalized Teukolsky equation for spin 0, 1/2 and 1 brane fields in the higher dimensional Kerr geometry and explicitly show that it is separable in any dimensions. For five-dimensional (Randall-Sundrum) black hole, we obtain analytic formulae for the greybody factors in low frequency expansion and we present the power spectra of the Hawking radiation as well as their angular dependence. Phenomenological implications of our result are briefly sketched.

hep-th

Alternative Signature of TeV Strings

In string theory, it is well known that any hard scattering amplitude inevitably suffers exponential suppression. We demonstrate that, if the string scale is M_s < 2TeV, this intrinsically stringy behavior leads to a dramatic reduction in the QCD jet production rate with very high transverse momenta p_T > 2TeV at LHC. This suppression is sufficient to be observed in the first year of low-luminosity running. Our prediction is based on the universal behavior of string theory, and therefore is qualitatively model-independent. This signature is alternative and complementary to conventional ones such as Regge resonance (or string ball/black hole) production.

hep-ph

Neutrino Masses in the Supersymmetric Standard Model with Right-Handed Neutrinos and Spontaneous R-Parity Violation

We propose an extension of the supersymmetric standard model with right-handed neutrinos and a singlet Higgs field, and study the neutrino masses in this model. The Majorana masses for the right-handed neutrinos are generated around the supersymmetry breaking scale through the vacuum expectation value of the singlet Higgs field. This model may induce spontaneous R-parity violation via the vacuum expectation value of the right-handed sneutrino. In the case, the effective theory is similar to a bilinear R-parity violating model. There are two sources for the neutrino masses: one is this bilinear R-parity breaking effect, and the other is the ordinary seesaw effect between left- and right-handed neutrinos. Combining these two effects, the hierarchical neutrino mass pattern arises even when the neutrino Yukawa matrices are not hierarchical. We acquire appropriate masses and mixings to explain both the solar and atmospheric neutrino oscillations.

hep-ph

Unified Explanation of Quark and Lepton Masses and Mixings in the Supersymmetric SO(10) Model

We discussed neutrino masses and mixings in SUSY SO(10) model where quarks and leptons have Yukawa couplings to at least two 10 and one $\bar{126}$ Higgs scalars. In this model, the Dirac and the right-handed Majorana mass terms are expressed by linear combinations of quark and charged lepton mass matrices, which then determine the neutrino mass matrix by the see-saw mechanism. We show that there are various solutions to reproduce a large mixing angle for $ν_μ-ν_τ$ and a small mixing angle for $ν_e-ν_μ$, as well as the hierarchical mass spectrum of neutrinos.

hep-ph