Simulating 2+1d Lattice QED with dynamical matter using ultracold atoms

We suggest a method to simulate lattice compact Quantum Electrodynamics (cQED) using ultracold atoms in optical lattices, which includes dynamical Dirac fermions in 2+1 dimensions. This allows to test dynamical effects of confinement as well as 2d flux loops deformations and breaking, and to observe Wilson-loop area-law.Comment: Includes supplementary material. Added references, minor modification

Pengaruh Paduan Abu Batubara Dengan Pasir Inti Cor Bekas Terhadap Konduktivitas Termal, Tahanan Termal, Dan Kuat Tekan Sebagai Bahan Refractory

Permasalahan limbah yang sulit terpecahkan seiring dengan pesatnya kemajuan industri sekarang ini menjadi salah satu alasan dilakukannya studi pemanfaatan limbah menjadi barang berdaya guna tinggi. Dalam penelitian ini, abu batubara dan pasir inti cor bekas merupakan dua obyek pemanfaatan limbah yang berdasarkan sifat mekanis dan karakteristiknya berpotensi menjadi bahan alternatif pembuatan refraktori/bata tahan api berbahan dasar tanah liat. Penelitian ini bertujuan untuk mengetahui pengaruh paduan terhadap konduktivitas termal, tahanan termal, dan kekuatan tekan sebagai bahan refraktori. Proses preparasi paduan dimulai dari proses penjemuran bahan baku (abu batubara dan pasir inti cor bekas) hingga kering, kemudian ditumbuk atau digerus dan diayak sampai ke tahap screening hingga memperoleh ukuran serbuk mesh 50, 100, & 200. Semua bahan kemudian dicampur secara manual dengan variasi komposisi abu-silika (%) 5:45, 10:40, 15:35, 20:30, 25:25, dan tanah liat 50%.. Selanjutnya sebelum paduan dibakar dilakukan proses pembentukan dengan metode cetak tekan menggunakan hidroulik press sebesar 80 kg/cm3 (silinder 2,5x3 cm dan balok 2x2x2 cm). Suhu sintering atau pembakaran dari paduan adalah 1000 °C. Analisa dan pengukuran benda uji yang dilakukan antara lain: analisa fasa dengan XRD, konduktivitas termal, tahanan termal, kekuatan tekan, dan mikro struktur dengan SEM. Hasil pengamatan menunjukkan bahwa dalam ketiga bahan tersebut terdapat kandungan mineral dominan yang sama yakni SiO2 dengan fasa Quartz, low. Hasil pengukuran sifat-sifatnya menunjukkan harga konduktivitas termal minimum (terbaik) dan tahanan termal maximum (terbaik) ada pada variabel mesh 50, komposisi AB 25%, Si 25%, TL 50% dengan masing-masing sebesar 22,36 W/mK dan 125 °C/W , sedangkan nilai kuat tekan (σ) maksimum (terbaik) ada pada variabel mesh 100, komposisi AB 15%, Si 35%, TL 50% sebesar 8,81 MPa (N/mm²). Pengaruh ukuran serbuk dan komposisi abu batubara dengan pasir inti cor bekas memberikan nilai konduktivitas termal cenderung menurun, sedangkan nilai tahanan termal dan kuat tekan cenderung meningkat. Berdasarkan analisa dan hasil-hasil yang diperoleh menunjukkan bahwa refraktori yang dibuat cukup memberi nilai guna lebih terhadap limbah (abu batubara dan pasir inti cor bekas) sebagai bahan alternatif pembuatan refraktori

Quantum Mechanical Realization of a Popescu-Rohrlich Box

We consider quantum ensembles which are determined by pre- and post-selection. Unlike the case of only pre-selected ensembles, we show that in this case the probabilities for measurement outcomes at intermediate times satisfy causality only rarely; such ensembles can in general be used to signal between causally disconnected regions. We show that under restrictive conditions, there are certain non-trivial bi-partite ensembles which do satisfy causality. These ensembles give rise to a violation of the CHSH inequality, which exceeds the maximal quantum violation given by Tsirelson's bound, $B_{\rm CHSH}\le 2\sqrt2$, and obtains the Popescu-Rohrlich bound for the maximal violation, $B_{\rm CHSH}\le 4$. This may be regarded as an a posteriori realization of super-correlations, which have recently been termed Popescu-Rohrlich boxes.Comment: 5 page

Not So SuperDense Coding - Deterministic Dense Coding with Partially Entangled States

The utilization of a $d$-level partially entangled state, shared by two parties wishing to communicate classical information without errors over a noiseless quantum channel, is discussed. We analytically construct deterministic dense coding schemes for certain classes of non-maximally entangled states, and numerically obtain schemes in the general case. We study the dependency of the information capacity of such schemes on the partially entangled state shared by the two parties. Surprisingly, for $d>2$ it is possible to have deterministic dense coding with less than one ebit. In this case the number of alphabet letters that can be communicated by a single particle, is between $d$ and 2d. In general we show that the alphabet size grows in "steps" with the possible values $d, d+1, ..., d^2-2$. We also find that states with less entanglement can have greater communication capacity than other more entangled states.Comment: 6 pages, 2 figures, submitted to Phys. Rev.

Feeding strategy and ontogenetic changes in diet of gurnards (Teleostea: Scorpaeniformes: Triglidae) from the Adriatic Sea

A multi-specific approach in fish diet studies provides insight into the complexity of trophic interactions in marine communities. The feeding habits of three gurnard species, Aspitrigla cuculus, Chelidonichthys lucerna and Eutrigla gurnardus (Scorpaeniformes: Triglidae), from the north-middle Adriatic Sea were studied to evaluate prey-resource partitioning amongst species and within species, comparing juveniles' and adults' diet for each gurnard species. A total of 1818 specimens (390 A. cuculus, 973 C. lucerna, 455 E. gurnardus) were collected by bottom trawling and they were assigned to size classes (juveniles or adults) on the basis of macroscopic evaluation of the gonads. Stomach contents were analysed. A common dietary preference for Crustacea was found in all species and size classes considered. Nevertheless, gurnards showed distinct feeding behaviour: C. lucerna and E. gurnardus were generalist-opportunistic predators, showing a varied diet based on epi-benthic, bentho-pelagic and necto-benthic preys belonging to different taxa such as Teleostei and Mollusca, while A. cuculus may be considered a specialist feeder, feeding almost exclusively on necto-benthic invertebrates. Morisita's index calculated for critical size classes (juveniles and adults) pointed out differences. At the inter-specific level, possible dietary competition between A. cuculus and E. gurnardus (C > 0.65) was found for all size classes combined, due to the prey abundance of Lophogaster typicus (Crustacea: Mysida). At the intra-specific level, high diet overlap was found between juveniles and adults of C. cuculus (C = 0.98) and between juveniles and adults of E. gurnardus (C > 0.84). In contrast, C. lucerna did not compete with increasing body size (C < 0.20), showing a clear change from crustaceans to fish in its diet preferences. The possibility that A. cuculus and E. gurnardus may compete for the same prey resources while C. lucerna shows food resource partitioning is discussed. Better understanding of the ecology of these coexisting predators should lead to improved conservation and improved fisheries management

``Weighing'' a closed system and the time-energy uncertainty principle

A gedanken-experiment is proposed for `weighing'' the total mass of a closed system from within the system. We prove that for an internal observer the time $\tau$, required to measure the total energy with accuracy $\Delta E$, is bounded according to $\tau \Delta E >\hbar$. This time-energy uncertainty principle for a closed system follows from the measurement back-reaction on the system. We generally examine what other conserved observables are in principle measurable within a closed system and what are the corresponding uncertainty relations.Comment: 8 page

The Fermi Problem in Discrete Systems

The Fermi two-atom problem illustrates an apparent causality violation in Quantum Field Theory which has to do with the nature of the built in correlations in the vacuum. It has been a constant subject of theoretical debate and discussions during the last few decades. Nevertheless, although the issues at hand could in principle be tested experimentally, the smallness of such apparent violations of causality in Quantum Electrodynamics prevented the observation of the predicted effect. In the present paper we show that the problem can be simulated within the framework of discrete systems that can be manifested, for instance, by trapped atoms in optical lattices or trapped ions. Unlike the original continuum case, the causal structure is no longer sharp. Nevertheless, as we show, it is possible to distinguish between "trivial" effects due to "direct" causality violations, and the effects associated with Fermi's problem, even in such discrete settings. The ability to control externally the strength of the atom-field interactions, enables us also to study both the original Fermi problem with "bare atoms", as well as correction in the scenario that involves "dressed" atoms. Finally, we show that in principle, the Fermi effect can be detected using trapped ions.Comment: Second version - minor change

Strategi Pemerintah Daerah dalam Pengembangan Kawasan Wisata Muara Kabupaten Tapanuli Utara Provinsi Sumatera Utara Tahun 2015

Based on the Medium Term Development Plan of North Tapanuli Regency Year 2014-2019, established Vision makes North Tapanuli as a tourist destination, one of which is the development of tourist areas Muara. In its development until 2015, several programs and activities in realizing the North Tapanuli as a tourist destination especially Muara travel area development can not be realized with the maximum. The purpose of this study to determine the strategy of local governments in the development of the tourist area of Muara 2015 and the factors that affect the implementation of tourism development Muara 2015. The research was qualitative descriptive research data collection is by interview and documentation, or the document search , The theory used in this research is the theory of government management, strategy theory and the theory of the development of tourism. From the results of the field studies showed that some programs and activities in the development of the tourist area of Muara not running maximum, there's even a program that does not bejalan due to lack of budget or funds obtained by the Department of Tourism and Culture of North Tapanuli. The factors that affect the implementation of tourism development Muara based on theory and management strategies of government, namely: lack of awareness, lack of funds, lack of human resources, and the lack of supporting facilities. The local government should conduct an evaluation of the programs can not be implemented so that the next policy can be more effective