CRAB Cavity in CERN SPS

Beam collisions with a crossing angle at the interaction point have been applied in high intensity colliders to reduce the effects of parasitic collisions which induce emittance growth and beam lifetime deterioration. The crossing angle causes the geometrical reduction of the luminosity. Crab cavity can be one of the most promising ways to compensate the crossing angle and to realize effective head-on collisions. Moreover, the crab crossing mitigates the synchro-betatron resonances due to the crossing angle. Crab cavity experiment in SPS is proposed for deciding on a full crab-cavity implementation in LHC. In this paper, we investigate the effects of crab crossing on beam dynamics and its life time with the global scheme.Comment: 3 pp. 1st International Particle Accelerator Conference: IPAC'10, 23-28 May 2010: Kyoto, Japa

D-Brane Probe and Closed String Tachyons

We consider a D-brane probe in unstable string background associated with flux branes. The twist in spacetime metric reponsible for the supersymmetry breaking is shown to manifest itself in mixing of open Wilson lines with the phases of some adjoint matter fields, resulting in a nonlocal and nonsupersymmetric form of Yang-Mills theory as the probe dynamics. This provides a setup where one can study fate of a large class of unstable closed string theories that include as a limit type 0 theories and various orbifolds of type II and type 0 theories. We discuss the limit of ${\bf C}/Z_n$ orbifold in some detail and speculate on couplings with closed string tachyons.Comment: LaTeX, 17 pages, typos fixed, references update

Black Hole Solutions in Heterotic String Theory on a Torus

We construct the general electrically charged, rotating black hole solution in the heterotic string theory compactified on a six dimensional torus and study its classical properties. This black hole is characterized by its mass, angular momentum, and a 28 dimensional electric charge vector. We recover the axion-dilaton black holes and Kaluza-Klein black holes for special values of the charge vector. For a generic black hole of this kind, the 28 dimensional magnetic dipole moment vector is not proportional to the electric charge vector, and we need two different gyromagnetic ratios for specifying the relation between these two vectors. We also give an algorithm for constructing a 58 parameter rotating dyonic black hole solution in this theory, characterized by its mass, angular momentum, a 28 dimensional electric charge vector and a 28 dimensional magnetic charge vector. This is the most general asymptotically flat black hole solution in this theory consistent with the no-hair theorem.Comment: LaTeX, 20 pages, A paragraph added discussing the relatioship between area of the stretched horizon and density of string states in the extremal limi

Energy Momentum Tensor and Marginal Deformations in Open String Field Theory

Marginal boundary deformations in a two dimensional conformal field theory correspond to a family of classical solutions of the equations of motion of open string field theory. In this paper we develop a systematic method for relating the parameter labelling the marginal boundary deformation in the conformal field theory to the parameter labelling the classical solution in open string field theory. This is done by first constructing the energy-momentum tensor associated with the classical solution in open string field theory using Noether method, and then comparing this to the answer obtained in the conformal field theory by analysing the boundary state. We also use this method to demonstrate that in open string field theory the tachyon lump solution on a circle of radius larger than one has vanishing pressure along the circle direction, as is expected for a codimension one D-brane.Comment: LaTeX file, 25 pages; v2: minor addition

The Transfer Paradox in a One-Sector Overlapping Generations Model

This paper examines the effects of international income transfers on welfare and capital accumulation in a one-sector overlapping generations model. It is shown that a strong form of the transfer paradox-- in which the donor country experiences a welfare gain while the recipient country experiences a welfare loss—may occur both in and out of steady state. In addition, it is shown that a weak form of the transfer paradox—where either the donor or recipient (but not both) experience paradoxical welfare effects—may characterize all segments of the transition path not already characterized by the strong transfer paradox. The results are explained by the effects of transfers on world capital accumulation and the world interest rate, which imply secondary intertemporal welfare effects large enough to dominate the initial effects of the income transfer.Transfer problem, transfer paradox, dynamics, one-sector overlapping generations model

Discrete gravity and and its continuum limit

Recently Gambini and Pullin proposed a new consistent discrete approach to quantum gravity and applied it to cosmological models. One remarkable result of this approach is that the cosmological singularity can be avoided in a general fashion. However, whether the continuum limit of such discretized theories exists is model dependent. In the case of massless scalar field coupled to gravity with $\Lambda=0$, the continuum limit can only be achieved by fine tuning the recurrence constant. We regard this failure as the implication that cosmological constant should vary with time. For this reason we replace the massless scalar field by Chaplygin gas which may contribute an effective cosmological constant term with the evolution of the universe. It turns out that the continuum limit can be reached in this case indeed.Comment: 16 pages,revised version published in MPL