Do subleading corrections to Bekenstein-Hawking entropy hold the key to quantum gravity?

Black-holes are considered to be theoretical laboratories for testing models of quantum gravity. It is usually believed that any candidate for quantum gravity must explain the microscopic origin of the Bekenstein-Hawking ($S_{_{\rm BH}}$) entropy. In this letter, we argue (i) the requirement for a candidate approach to go beyond $S_{_{\rm BH}}$ and provide generic subleading corrections, and (ii) the importance to {\it disentangle} and identify the degrees of freedom leading to $S_{_{\rm BH}}$ and its subleading corrections. Using the approach of entanglement of modes across the horizon, we show that the microscopic degrees of freedom that lead to $S_{_{\rm BH}}$ and subleading corrections are different. We further show, using microcanonical and canonical ensemble approaches, that the quantum entanglement predicts generic power-law corrections to $S_{_{\rm BH}}$ and that the corrections can be identified with the kinematical properties of the event-horizon.Comment: 6 pages, Final version, To appear in MPL

Web-interfaced Nonlinear Optical Waveguide and Photonic Crystal Simulator

We report on the development of new methods for the computation of spectral bandpass properties of photonic crystals and for the electromagnetic wave propagation in second order nonlinear optical waveguides. The former is based on a generalization of characteristic matrices while the latter is based on path integrals. Accurate and efficient propagation methods and algorithms form the basis for the construction of design tools for integrated optics

Linux kernel compaction through cold code swapping

There is a growing trend to use general-purpose operating systems like Linux in embedded systems. Previous research focused on using compaction and specialization techniques to adapt a general-purpose OS to the memory-constrained environment, presented by most, embedded systems. However, there is still room for improvement: it has been shown that even after application of the aforementioned techniques more than 50% of the kernel code remains unexecuted under normal system operation. We introduce a new technique that reduces the Linux kernel code memory footprint, through on-demand code loading of infrequently executed code, for systems that support virtual memory. In this paper, we describe our general approach, and we study code placement algorithms to minimize the performance impact of the code loading. A code, size reduction of 68% is achieved, with a 2.2% execution speedup of the system-mode execution time, for a case study based on the MediaBench II benchmark suite

Spatially asymptotic S-matrix from general boundary formulation

We construct a new type of S-matrix in quantum field theory using the general boundary formulation. In contrast to the usual S-matrix the space of free asymptotic states is located at spatial rather than at temporal infinity. Hence, the new S-matrix applies to situations where interactions may remain important at all times, but become negligible with distance. We show that the new S-matrix is equivalent to the usual one in situations where both apply. This equivalence is mediated by an isomorphism between the respective asymptotic state spaces that we construct. We introduce coherent states that allow us to obtain explicit expressions for the new S-matrix. In our formalism crossing symmetry becomes a manifest rather than a derived feature of the S-matrix.Comment: 27 pages, LaTeX + revtex4; v2: various corrections, references update

Partition Function for (2+1)-Dimensional Einstein Gravity

Taking (2+1)-dimensional pure Einstein gravity for arbitrary genus $g$ as a model, we investigate the relation between the partition function formally defined on the entire phase space and the one written in terms of the reduced phase space. In particular the case of $g=1$ is analyzed in detail. By a suitable gauge-fixing, the partition function $Z$ basically reduces to the partition function defined for the reduced system, whose dynamical variables are $(\tau^A, p_A)$. [The $\tau^A$'s are the Teichm\"uller parameters, and the $p_A$'s are their conjugate momenta.] As for the case of $g=1$, we find out that $Z$ is also related with another reduced form, whose dynamical variables are $(\tau^A, p_A)$ and $(V, \sigma)$. [Here $\sigma$ is a conjugate momentum to 2-volume $V$.] A nontrivial factor appears in the measure in terms of this type of reduced form. The factor turns out to be a Faddeev-Popov determinant coming from the time-reparameterization invariance inherent in this type of formulation. Thus the relation between two reduced forms becomes transparent even in the context of quantum theory. Furthermore for $g=1$, a factor coming from the zero-modes of a differential operator $P_1$ can appear in the path-integral measure in the reduced representation of $Z$. It depends on the path-integral domain for the shift vector in $Z$: If it is defined to include $\ker P_1$, the nontrivial factor does not appear. On the other hand, if the integral domain is defined to exclude $\ker P_1$, the factor appears in the measure. This factor can depend on the dynamical variables, typically as a function of $V$, and can influence the semiclassical dynamics of the (2+1)-dimensional spacetime. These results shall be significant from the viewpoint of quantum gravity.Comment: 21 pages. To appear in Physical Review D. The discussion on the path-integral domain for the shift vector has been adde

Mineral sinks within ripening grape berries (Vitis vinifera L.)

Trends in the accumulation of mineral elements into the grape berry components give information about vascular flow into the berry. Shiraz berries were dissected into receptacle, skin, pulp, brush and seeds and the accumulation of 10 mineral elements into these components was followed through development. The elements were separated into two categories according to their accumulation pattern into the berry. The first group of elements continued to accumulate throughout berry growth and ripening, and was comprised of  phloem-mobile potassium, phosphorus, sulphur, magnesium, boron, iron and copper. The second group of elements accumulated mostly prior to veraison, and included the xylem-mobile minerals calcium, manganese and zinc. These results indicate that the xylem contribution to berry growth diminished after veraison. Berry fresh weight, dry weight, as well as berry sugar content, were all highly correlated with berry potassium content. While the pulp and skin were the strongest sinks for potassium and boron, seeds were the strongest sinks for calcium, phosphorus, sulphur, manganese and zinc. With the exception of calcium and manganese, seeds ceased to accumulate most elements during late ripening. The berry receptacle and brush did not accumulate any of the elements to levels above those of the other berry components at any stage of development. Therefore, they did not act as sinks for xylem- or phloem-mobile elements as vascular flow to the pulp and skin slowed.

Valence band offset of the ZnO/AlN heterojunction determined by X-ray photoemission spectroscopy

The valence band offset of ZnO/AlN heterojunctions is determined by high resolution x-ray photoemission spectroscopy. The valence band of ZnO is found to be 0.43±0.17 eV below that of AlN. Together with the resulting conduction band offset of 3.29±0.20 eV, this indicates that a type-II (staggered) band line up exists at the ZnO/AlN heterojunction. Using the III-nitride band offsets and the transitivity rule, the valence band offsets for ZnO/GaN and ZnO/InN heterojunctions are derived as 1.37 and 1.95 eV, respectively, significantly higher than the previously determined values