Black Hole as an Information Eraser
We discuss the identity of black hole entropy and show that the first law of black hole thermodynamics, in the case of a Schwarzschild black hole, can be derived from Landauer's principle by assuming that the black hole is one of the most efficient information erasers. The term "most efficient" implies that maximal information will be erased for a given amount of work. We calculate the discrete mass spectra and the entropy of a Schwarzschild black hole assuming that the black hole processes information in unit of bits. The black hole entropy acquires a subleading contribution proportional to the logarithm of its mass-squared in addition to the usual mass-squared term without an artificial cutoff. We also argue that the minimum of the black hole mass is $\sqrt{\log 2/(8\pi)}M_{\rm P}$.

title: Radiation Damping at a Bubble Wall
abstract: The first order phase transition proceeds via nucleation and growth of true vacuum bubbles. When charged particles collide with the bubble they could radiate electromagnetic wave. We show that, due to an energy loss of the particles by the radiation, the damping pressure acting on the bubble wall depends on the velocity of the wall even in a thermal equilibrium state.

title: Zero cosmological constant and nonzero dark energy from the holographic principle
abstract: The first law of thermodynamics and the holographic principle applied to an arbitrary large cosmic causal horizon are shown to naturally demand a zero cosmological constant and a non-zero dynamical dark energy in the form of the holographic dark energy. A semiclassical analysis shows that the holographic dark energy has a parameter d = 1 and an equation of state comparable to current observational data if the entropy of the horizon saturates the Bekenstein-Hawking bound. This result indicates that quantum field theory should be modified on a large scale to explain the dark energy. The relations among the dark energy, the quantum vacuum energy and the entropic gravity are also discussed.

title: Dark energy from forgetting
abstract: We suggest that dark energy has a quantum informational origin. Landauer's principle associated with the erasure of quantum information at a cosmic horizon implies the non-zero vacuum energy having effective negative pressure. Assuming the holographic principle, the minimum free energy condition, and the Gibbons-Hawking temperature for the cosmic event horizon we obtain the holographic dark energy with the parameter $d\simeq 1$, which is consistent with the current observational data. It is also shown that both the entanglement energy and the horizon energy can be related to Landauer's principle.

title: Quantum entanglement from the holographic principle
abstract: It is suggested that quantum entanglement emerges from the holographic principle stating that all of the information of a region (bulk bits) can be described by the bits on its boundary surface. There are redundancy and information loss in the bulk bits that lead to the nonlocal correlation among the bulk bits. Quantum field theory overestimates the independent degrees of freedom in the bulk. The maximum entanglement in the universe increases as the size of the cosmic horizon and this could be related with the arrow of time and dark energy.

title: BEC dark matter can explain collisions of galaxy clusters
abstract: We suggest that the dark matter model based on Bose Einstein condensate or scalar field can resolve the apparently contradictory behaviors of dark matter in the Abell 520 and the Bullet cluster. During a collision of two galaxies in the cluster, if initial kinetic energy of the galaxies is large enough, two dark matter halos pass each other in a soliton-like way as observed in the Bullet cluster. If not, the halos merge due to the tiny repulsive interaction among dark matter particles as observed in the Abell 520. This idea can also explain the origin of the dark galaxy and the galaxy without dark matter.

title: Gaugino masses from gravitino at one loop
abstract: The N=1 supergravity coupled to chiral and Yang-Mills superfields is regarded as the ultraviolet theory of the supersymmetric Standard Model. The gravitino acquires a mass from the hidden sector and participate in mediating supersymmetry breaking to the visible sector. We consider the quantum effects of the gravitino and evaluate its contribution to the gaugino masses at one loop level, which turns out to be irrespective of the SM gauge couplings. Due to the universality of gravitino, its contribution to the gaugino masses can significantly modify the gaugino mass relations of other supersymmetry breaking mechanisms depending on the gravitino mass. For a given gaugino mass the gravitino mass cannot be arbitrarily large even when other supersymmetry breaking mechanisms are dominant.

title: R-parity violation and semileptonic decays of B-meson
abstract: We investigate the effects of R -parity violation on the semileptonic decays of B -meson in the minimal supersymmetric standard model with explicit R -parity violation and discuss its physical implications. We find that the semileptonic decays of B -meson can be largely affected by R -parity violation.

title: Global and local D-vortices
abstract: Codimension-two objects on a system of brane-antibrane are studied in the context of Born-Infeld type effective field theory with a complex tachyon and U(1) × U(1) gauge fields. When the radial electric field is turned on in D2 ¯ D2, we find static regular global and local D-vortex solutions which could be candidates of straight cosmic D-strings in a superstring theory. A natural extension to DF-strings is briefly discussed.

title: Invariant-mass distribution of c anti-c in Upsilon(1S) ---> c anti-c + X

title: Classical stability of black D3-branes
abstract: We have investigated the classical stability of charged black D3-branes in the type-IIB supergravity under small perturbations. For s-wave perturbations it turns out that black D3-branes are unstable when they have small charge density. As the charge density increases for given mass density, however, the instability decreases down to zero at a certain finite value of the charge density, and then black D3-branes become stable all the way down to the extremal point. It has also been shown that such critical value at which its stability behavior changes agrees very well with the predicted one by the thermodynamic stability behavior of the corresponding black hole system through the Gubser-Mitra conjecture. Unstable mode solutions we found involve non-vanishing fluctuations of the self-dual five-form field strength. Some implications of our results are also discussed.