We generalize the computations of the long-range interactions between two parallel stacks of branes in [1, 2] to various cases when two stacks of branes are not placed parallel to each other. We classify the nature of interaction (repulsive or attractive) for each special case and this classification can be used to justify the nature of long-range interaction between two complicated brane systems such as brane bound states. We will provide explicit examples in this paper to demonstrate this.
We study the cosmology of a quintessence scalar field which is equivalent to a non-barotropic perfect fluid of constant pressure. The coincidence problem is alleviated by such a quintessence equation-of-state that interpolates between plateau of zero at large redshifts and plateau of minus one as the redshift approaches to zero. The quintessence field is neither a unified dark matter nor a mixture of cosmological constant and cold dark matter, relying on the facts that the quintessence density contrasts of sub-horizon modes would undergo a period of late-time decline and the squared sound speeds of quintessence perturbations do not vanish. What a role does the quintessence play is dynamic dark energy, its clustering could remarkably reduce the growth rate of the density perturbations of non-relativistic matters.
It is well known that charged black Dp branes of type II string theory share a universal phase structure of van der Waals−Maxwell liquid-gas type except D5 and D6 branes. Interestingly, the phase structure of D5 and D6 branes can be changed to the universal form with the inclusion of particular delocalized charged lower-dimensional branes. For D5 branes one needs to introduce delocalized D1 branes, and for D6 branes, one needs to introduce delocalized D0 branes to obtain the universal structure. In a previous paper [J. High Energy Phys. 04 (2013) 100] Lu with Wei study the phase structure of black D6 branes with the introduction of delocalized D0 branes in a special case when their charges are equal and the dilaton charge vanishes. In this paper, we look at the phase structure of the black D6/D0 system with the generic values of the parameters, which makes the analysis more involved but the structure more rich. We also provide reasons why the respective modifications of the phase structures to the universal form for the black D5 and D6 branes occur when specific delocalized lower-dimensional branes are introduced.
We study the cosmology of a quintessence scalar field which is equivalent to a non-barotropic perfect fluid of constant pressure. The coincidence problem is alleviated by such a quintessence equation-of-state that interpolates between plateau of zero at large redshifts and plateau of minus one as the redshift approaches to zero. The quintessence field is neither a unified dark matter nor a mixture of cosmological constant and cold dark matter, relying on the facts that the quintessence density contrasts of sub-horizon modes would undergo a period of late-time decline and the squared sound speeds of quintessence perturbations do not vanish. What a role does the quintessence play is dynamic dark energy, its clustering could remarkably reduce the growth rate of the density perturbations of non-relativistic matters.
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