Quantum States, Thermodynamic Limits and Entropy in M-Theory

We discuss the matching of the BPS part of the spectrum for (super)membrane, which gives the possibility of getting membrane's results via string calculations. In the small coupling limit of M--theory the entropy of the system coincides with the standard entropy of type IIB string theory (including the logarithmic correction term). The thermodynamic behavior at large coupling constant is computed by considering M--theory on a manifold with topology ${\mathbb T}^2\times{\mathbb R}^9$. We argue that the finite temperature partition functions (brane Laurent series for $p \neq 1$) associated with BPS $p-$brane spectrum can be analytically continued to well--defined functionals. It means that a finite temperature can be introduced in brane theory, which behaves like finite temperature field theory. In the limit $p \to 0$ (point particle limit) it gives rise to the standard behavior of thermodynamic quantities.Comment: 7 pages, no figures, Revtex style. To be published in the Physical Review

Technical Requirements for Connecting Solar Power Plants to Electricity Networks

This chapter discusses basics of technical design specifications, criteria, technical terms and equipment parameters required to connect solar power plants to electricity networks. Depending on its capacity, a solar plant can be connected to LV, MV, or HV networks. Successful connection of a medium-scale solar plant should satisfy requirements of both the Solar Energy Grid Connection Code (SEGCC) and the appropriate code: the Electricity Distribution Code (EDC) or the Grid Code (GC) as the connection level apply. Connection of a large-scale solar plant to the transmission network should satisfy the requirements of both SEGCC and GC. For Small-Scale Photovoltaic (SSPV), the connection should satisfy both the SSPV Connection Code and the EDC. The objectives are to establish the obligations and responsibilities of each party; i.e. operators and all network users, thus leading to improved security, higher reliability and maintaining optimal operation. The technical specifications include permitted voltage and frequency variations in addition to power quality limits of harmonic distortion, phase unbalance, and flickers. Operational limits and capability requirements will be explained and discussed. Solar power grid connection codes of Egypt are explored first. Finally, brief comparisons of PV codes and related codes of UK, Germany, USA, and Egypt are presented

Black Hole Entropy Associated with Supersymmetric Sigma Model

By means of an identity that equates elliptic genus partition function of a supersymmetric sigma model on the $N$-fold symmetric product $S^N X$ of $X$ ($S^N X=X^N/S_N$, $S_N$ is the symmetric group of $N$ elements) to the partition function of a second quantized string theory, we derive the asymptotic expansion of the partition function as well as the asymptotic for the degeneracy of spectrum in string theory. The asymptotic expansion for the state counting reproduces the logarithmic correction to the black hole entropy.Comment: 11 pages, no figures, version to appear in the Phys. Rev. D (2003

Effect of production systems on the performance of dairy cows in the Gezira State, Sudan

      This study was conducted in the Gezira State, Sudan, with the objectives of investigating and comparing the  effect of production  systems  on age  at first calving, calving interval, milk yield, herd structure, mortality and growth rate in traditional animal production and organized dairy farms. Six out of eight localities were included in the study. From each locality, 5 herds, each of traditional animal production and organized dairy farms were selected. This survey was carried out  using questionnaire involving 40 farmers (including the surveyed farms) from each locality. Means and standard deviations for each studied parameter were calculated using SPSS. The result revealed greater differences in the studied parameters between the two systems of production. Feed had a great influence on animal performance. It could be recommended that, for improving the traditional farm performance, efforts should be payed  to upgrade animal genetics through selection from highly producing local cows and introduction of foreign breeds. Feeding improvement in both terms of quality and quantity is also needed. اجريت هذه الدراسة  بولاية الجزيرة بغرض التعرف ومقارنة أثر نظم الانتاج المختلفة علي العمر عند اول ولادة والفترة بين الولدتين وانتاج اللبن وتركيب القطيع والنفوق ومعدل النمو في كل من قطاع الانتاج الحيواني التقليدي ومزارع الالبان المنتظمة . شملت الدراسة ستة من ثمانية محليات. اختير من كل محلية 5 قطعان من كل من قطاع الانتاج الحيواني التقليدي ومزاع الالبان المنتظمة. دعم المسح باستبيان شمل 40 مزارع من كل محلية. حسبت المتوسطات والانحرافات المعيارية لكل عنصر من عناصر الدراسة وذلك باستخدام نظام الحزم الاحصائية للعلوم الاجتماعية (  (SPSS  كشفت الدراسة عن فروقات معنوية بين العناصر المدروسة في كل من النظاميين واكدت ان الغذاء له اثر كبير علي اداء الحيوان وكذلك العناصر الأخرى خاصة الوراثية قد يكون لها اثر علي الاداء. من اجل تحسين مزارع الانتاج الحيواني التقليدي توصي الدراسة تبذل مجهودات لرفع الكفاءة الوراثية للحيوان  من خلال الاختيار من الابقار المحلية العالية  الانتاج وادخال السلالات الاجنبية . أيضاً يجب رفع مستوي الغذاء من الناحية الكمية والنوعية.               &nbsp

Quantum properties of the parametric amplifier with and without pumping field fluctuations

The parametric amplifier with and without the pumping fluctuations of coupling function is considered when the fields are initially prepared in coherent light. The pumping fluctuations are assumed to be normally distributed with time-dependent variance. The effects of antibunching and anticorrelation of photons on the photon distribution, correlation between modes and factorial moments are demonstrated. A possible enhancement of photon antibunching for certain values of initial mean photon numbers is shown and discussed. We have shown also that new states (called modified squeezed vacuum states or even thermal states) can be generated from such an interaction. Further, we have demonstrated that the sum photon-number distribution can exhibit collapses and revivals in the photon-number domain somewhat similar to those known in the Jaynes-Cummings model.Comment: 17 pages, 6figure

Quantum properties of the codirectional three-mode Kerr nonlinear coupler

We investigate the quantum properties for the codirectional three-mode Kerr nonlinear coupler. We investigate single-, two- and three-mode quadrature squeezing, Wigner function and purity. We prove that this device can provide richer nonclassical effects than those produced by the conventional coupler, i.e. the two-mode Kerr coupler. We show that it can provide squeezing and the quadrature squeezing exhibiting leaf-revival-collapse phenomenon in dependence on the values of the interaction parameters. In contrast to the conventional Kerr coupler two different forms of cat states can be simultaneously generated in the waveguides. We deduce conditions required for the complete disentanglement between the components of the system.Comment: 23 pages, 6 figure

Squeezing properties of the Kerr-down conversion system

In this Letter we describe a new two-mode system, which consists of Kerr-like medium and down conversion process, called the Kerr-down conversion system. Under a certain condition we can obtain an exact solution of the dynamical equations of motion. For this system we investigate different kinds of quadrature squeezing, e.g., single-mode, two-mode and sum-squeezing. Also we give a more general definition of the principal squeezing. We show that the amounts of nonclassical effects produced by the Kerr-like and down-conversion processes separately are greater than those obtained from the Kerr-down conversion system where both the processes are in competition.Comment: 12 pages, 3 figure

Quantum properties of the three-mode squeezed operator: triply concurrent parametric amplifiers

In this paper, we study the quantum properties of the three-mode squeezed operator. This operator is constructed from the optical parametric oscillator based on the three concurrent $\chi^{(2)}$ nonlinearities. We give a complete treatment for this operator including the symmetric and asymmetric nonlinearities cases. The action of the operator on the number and coherent states are studied in the framework of squeezing, second-order correlation function, Cauchy-Schwartz inequality and single-mode quasiprobability function. The nonclassical effects are remarkable in all these quantities. We show that the nonclassical effects generated by the asymmetric case--for certain values of the system parameters--are greater than those of the symmetric one. This reflects the important role for the asymmetry in the system. Moreover, the system can generate different types of the Schr\"odinger-cat states.Comment: 21 pages, 14 figures; comments are most welcom

Spectrum of confining strings in SU(N) gauge theories

We study the spectrum of the confining strings in four-dimensional SU(N) gauge theories. We compute, for the SU(4) and SU(6) gauge theories formulated on a lattice, the string tensions sigma_k related to sources with Z_N charge k, using Monte Carlo simulations. Our results are consistent with the sine formula sigma_k/sigma = sin k pi/N / sin pi/N for the ratio between sigma_k and the standard string tension sigma. For the SU(4) and SU(6) cases the accuracy is approximately 1% and 2%, respectively. The sine formula is known to emerge in various realizations of supersymmetric SU(N) gauge theories. On the other hand, our results show deviations from Casimir scaling. We also discuss an analogous behavior exhibited by two-dimensional SU(N) x SU(N) chiral models.Comment: Latex, 34 pages, 10 figures. Results of new SU(4) simulations added. The new data are included in the analysis, leading to improved final estimates for SU(4). Conclusions unchange

A Search for Correlation of Ultra-High Energy Cosmic Rays with IRAS-PSCz and 2MASS-6dF Galaxies

We study the arrival directions of 69 ultra-high energy cosmic rays (UHECRs) observed at the Pierre Auger Observatory (PAO) with energies exceeding 55 EeV. We investigate whether the UHECRs exhibit the anisotropy signal expected if the primary particles are protons that originate in galaxies in the local universe, or in sources correlated with these galaxies. We cross-correlate the UHECR arrival directions with the positions of IRAS-PSCz and 2MASS-6dF galaxies taking into account particle energy losses during propagation. This is the first time that the 6dF survey is used in a search for the sources of UHECRs and the first time that the PSCz survey is used with the full 69 PAO events. The observed cross-correlation signal is larger for the PAO UHECRs than for 94% (98%) of realisations from an isotropic distribution when cross-correlated with the PSCz (6dF). On the other hand the observed cross-correlation signal is lower than that expected from 85% of realisations, had the UHECRs originated in galaxies in either survey. The observed cross-correlation signal does exceed that expected by 50% of the realisations if the UHECRs are randomly deflected by intervening magnetic fields by 5 degrees or more. We propose a new method of analysing the expected anisotropy signal, by dividing the predicted UHECR source distribution into equal predicted flux radial shells, which can help localise and constrain the properties of UHECR sources. We find that the 69 PAO events are consistent with isotropy in the nearest of three shells we define, whereas there is weak evidence for correlation with the predicted source distribution in the two more distant shells in which the galaxy distribution is less anisotropic.Comment: 23 pages, version published in JCA