A not so brief commentary on cosmological entropy bounds

There has been, quite recently, a discussion on how holographic-inspired bounds might be used to encompass the present-day dark energy and early-universe inflation into a single paradigm. In the current treatment, we point out an inconsistency in the proposed framework and then provide a viable resolution. We also elaborate on some of the implications of this framework and further motivate the proposed holographic connection. The manuscript ends with a more speculative note on cosmic time as an emergent (holographically induced) construct.Comment: 12 pages and Revtex; (v2) reference added and a few cosmetic change

Tinie -- a software package for electronic transport through two-dimensional cavities in a magnetic field

Quantum transport has far-reaching applications in modern electronics as it enables the control of currents in nanoscale systems such as quantum dots. In this paper we introduce tinie: a state-of-the-art quantum transport simulation framework, which can efficiently perform first-principle calculations based on the Landauer-B\"uttiker formalism. The computational repertoire of tinie includes calculations of transmission, conductivity, and currents running through arbitrary multi-terminal two-dimensional transport devices, with additional tools that enable the computation of the local density of states. The generality of tinie ranges from wide-band approximation calculations to investigating systems subject to an external magnetic field. The future prospects of tinie include the simulation of, e.g., two-dimensional cavities, quantum dots, or molecular junctions. The package is written in Python 3.6, and its well-documented modular structure is designed with an intent to create a platform suited for continuous expansion and development. With tinie it is possible to obtain specific information about the effects of impurities and imperfections in quantum devices, particularly between ballistic and diffusive transport regimes

The interpretation of the solutions of the Wheeler De Witt equation

We extract transition amplitudes among matter constituents of the universe from the solutions of the Wheeler De Witt equation. The physical interpretation of these solutions is then reached by an analysis of the properties of the transition amplitudes. The interpretation so obtained is based on the current carried by these solutions and confirms ideas put forward by Vilenkin.Comment: 11 pages, latex, no figure

The Quantum Physics of Black Holes: Results from String Theory

We review recent progress in our understanding of the physics of black holes. In particular, we discuss the ideas from string theory that explain the entropy of black holes from a counting of microstates of the hole, and the related derivation of unitary Hawking radiation from such holes.Comment: 49 pages, Latex, 4 figures, (Review article

The Lorentz force between D0 and D6 branes in string and M(atrix) theory

We use different techniques to analyze the system formed by a D0 brane and a D6 brane (with background gauge fields) in relative motion. In particular, using the closed string formalism of boosted boundary states, we show the presence of a term linear in the velocity, corresponding to the Lorentz force experienced by the D0 brane moving in the magnetic background produced by the D6 brane. This term, that was missed in previous analyses of this system, comes entirely from the R-R odd spin structure and is also reproduced by a M(atrix) theory calculation.Comment: 13 pages, plain LaTeX; some clarifying comments and a reference adde

Probing a D6 + D0 state with D6-branes: SYM - Supergravity correspondence at subleading level

We probe a non-supersymmetric D6 + D0 state with D6-branes and find agreement at subleading order between the supergravity and super Yang-Mills description of the long-distance, low-velocity interaction.Comment: LaTeX, 15 pages, no figure

Cosmic holographic bounds with UV and IR cutoffs

We introduce the cosmic holographic bounds with two UV and IR cutoff scales, to deal with both the inflationary universe in the past and dark energy in the future. To describe quantum fluctuations of inflation on sub-horizon scales, we use the Bekenstein-Hawking energy bound. However, it is not justified that the D-bound is satisfied with the coarse-grained entropy. The Hubble bounds are introduced for classical fluctuations of inflation on super-horizon scales. It turns out that the Hubble entropy bound is satisfied with the entanglement entropy and the Hubble temperature bound leads to a condition for the slow-roll inflation. In order to describe the dark energy, we introduce the holographic energy density which is the one saturating the Bekenstein-Hawking energy bound for a weakly gravitating system. Here the UV (IR) cutoff is given by the Planck scale (future event horizon), respectively. As a result, we find the close connection between quantum and classical fluctuations of inflation, and dark energy.Comment: 15page

Optical Technologies for UV Remote Sensing Instruments

Over the last decade significant advances in technology have made possible development of instruments with substantially improved efficiency in the UV spectral region. In the area of optical coatings and materials, the importance of recent developments in chemical vapor deposited (CVD) silicon carbide (SiC) mirrors, SiC films, and multilayer coatings in the context of ultraviolet instrumentation design are discussed. For example, the development of chemically vapor deposited (CVD) silicon carbide (SiC) mirrors, with high ultraviolet (UV) reflectance and low scatter surfaces, provides the opportunity to extend higher spectral/spatial resolution capability into the 50-nm region. Optical coatings for normal incidence diffraction gratings are particularly important for the evolution of efficient extreme ultraviolet (EUV) spectrographs. SiC films are important for optimizing the spectrograph performance in the 90 nm spectral region. The performance evaluation of the flight optical components for the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument, a spectroscopic instrument to fly aboard the Solar and Heliospheric Observatory (SOHO) mission, designed to study dynamic processes, temperatures, and densities in the plasma of the upper atmosphere of the Sun in the wavelength range from 50 nm to 160 nm, is discussed. The optical components were evaluated for imaging and scatter in the UV. The performance evaluation of SOHO/CDS (Coronal Diagnostic Spectrometer) flight gratings tested for spectral resolution and scatter in the DGEF is reviewed and preliminary results on resolution and scatter testing of Space Telescope Imaging Spectrograph (STIS) technology development diffraction gratings are presented

On the Supergravity Gauge theory Correspondence and the Matrix Model

We review the assumptions and the logic underlying the derivation of DLCQ Matrix models. In particular we try to clarify what remains valid at finite $N$, the role of the non-renormalization theorems and higher order terms in the supergravity expansion. The relation to Maldacena's conjecture is also discussed. In particular the compactification of the Matrix model on $T_3$ is compared to the $AdS_5\times S_5$ ${\cal N}=4$ super Yang-Mills duality, and the different role of the branes in the two cases is pointed out.Comment: 19 pages, Late

Radiation via Tunneling from a de Sitter Cosmological Horizon

Hawking radiation can usefully be viewed as a semi-classical tunneling process that originates at the black hole horizon. The same basic premise should apply to de Sitter background radiation, with the cosmological horizon of de Sitter space now playing the featured role. In fact, a recent work [hep-th/0204107] has gone a long way to verifying the validity of this de Sitter-tunneling picture. In the current paper, we extend these prior considerations to arbitrary-dimensional de Sitter space, as well as Schwarzschild-de Sitter spacetimes. It is shown that the tunneling formalism naturally censors against any black hole with a mass in excess of the Nariai value; thus enforcing a ``third law'' of Schwarzschild-de Sitter thermodynamics. We also provide commentary on the dS/CFT correspondence in the context of this tunneling framework.Comment: 19 pages, Latex; citation added; Eqs.(36,37) correcte