Modern Physics Letters A

Globular clusters are gravitationally bound stellar systems containing on the order of 10⁵ stars. Due to the high stellar densities in the cores of these clusters, close encounters and even physical collisions between stars are inevitable. These dynamical interactions can produce exotic types of single and binary stars that are extremely rare in the galactic field, but which may be important to the dynamical evolution of their host clusters. A common feature of these dynamically-formed stellar populations is that many of their members are relatively hot, and thus bright in the far-ultraviolet (FUV) waveband. In this short review, we describe how space-based FUV observations are being used to find and study these populations.

The periodic bounce of Born–Infeld theory of D3-branes is derived, and the BPS limit of infinite period is discussed as an example of tachyon condensation. The explicit bounce solution to the Born–Infeld action is interpreted as an unstable fundamental string stretched between the brane and its antibrane.

This paper is the continuation of a study into the information paradox problem started by the author in his earlier works. As before, the key instrument is a deformed density matrix in quantum mechanics of the early universe. It is assumed that the latter represents quantum mechanics with fundamental length. It is demonstrated that the obtained results agree well with the canonical viewpoint that in the processes involving black holes pure states go to the mixed ones in the assumption that all measurements are performed by the observer in a well-known quantum mechanics. Also it is shown that high entropy for Planck's remnants of black holes appearing in the assumption of the generalized uncertainty relations may be explained within the scope of the density matrix entropy introduced by the author previously. It is noted that the suggested paradigm is consistent with the holographic principle. Because of this, a conjecture is made about the possibility for obtaining the generalized uncertainty relations from the covariant entropy bound at high energies in the same way as Bousso has derived Heisenberg's uncertainty principle for the flat space.

We demonstrate the procedure of finding the band edge eigenfunctions and eigenvalues of periodic potentials, through the quantum Hamilton–Jacobi formalism. The potentials studied here are the Lamé and associated Lamé, which belong to the class of elliptic potentials. The formalism requires an assumption about the singularity structure of the quantum momentum function p, obeying a Riccati type equation in the complex x-plane. Essential use is made of suitable conformal transformations, which lead to the eigenvalues and the eigenfunctions corresponding to the band edges, in a straightforward manner. Our study reveals interesting features about the singularity structure of p, underlying the band edge states.

We study D-branes in the background of a gravitational shock wave. We consider the case of parallel D-branes located on opposite sides with respect to the shock wave. Their interaction is studied by evaluating the cylinder diagram using the boundary states technique. Boundary states are defined at each D-brane and their scalar product is evaluated after propagation through the shock wave. Taking the limit where the gravitational shock wave vanishes, we show that the amplitude evaluated is consistent with the flat spacetime result.

We show that the Witten covariant phase space for p-branes with thickness in an arbitrary background is endowed of a symplectic potential, which although is not important to the dynamics of the system, plays a relevant role on the phase space, allowing us to generate a symplectic structure for the theory and therefore give a covariant description of canonical formalism for quantization.