AdS/CFT and Landau Fermi liquids

We study the field theory dual to a charged gravitational background in which the low temperature entropy scales linearly with the temperature. We exhibit the existence of a sound mode which is described by hydrodynamics, even at energies much larger than the temperature, and explain how this, and other properties of the field theory, are consistent with those of a (3+1)-dimensional Landau Fermi liquid, finely tuned to the Pomeranchuk critical point. We also discuss how one could engineer a higher-derivative gravitational Lagrangian which reproduces the correct low temperature behavior of shear viscosity in a generic Landau Fermi liquid.Comment: harvmac, 35 pages, 2 figures. v2: minor changes and references adde

Development of neural network models for the analysis of infocommunication traffic

This article discusses the problems of today’s infocommunication networks, the basis of which are multiservice networks serving all types of traffic, presented as a set of IP packets. The characteristic features of this traffic are analyzed, each of which is oriented to a certain class of services. The knowledge gained as a result of ongoing traffic research is an essential factor for increasing the effectiveness of decisions made in various fields of the telecommunications industry. The need for knowledge of the nature of traffic circulating in the network and the laws of its behavior is revealed and substantiated. Without this, it is impossible to effectively manage networks, develop solutions for their development, ensure network security and maintain the required level of quality. Despite the large number of works about building multi - service networks, a number of issues require further study. Analysis of traffic studies of modern converged, multiservice networks showed the lack of knowledge about its nature and laws of behavior, given the high variability of its characteristics. Thus, it can be argued that the parameters of the studied traffic are statistical, probabilistic in nature, can vary randomly over time and, accordingly, based on the study, the author proposes a study using statistical analysis methods. To study traffic, you should use the tools of probability theory and mathematical statistics

Anomalous Zero Sound

We show that the anomalous term in the current, recently suggested by Son and Yamamoto, modifies the structure of the zero sound mode in the Fermi liquid in a magnetic field.Comment: 14 pages, 2 figure

Excitonic Emission of Monolayer Semiconductors Near-Field Coupled to High-Q Microresonators.

We present quantum yield measurements of single layer WSe2 (1L-WSe2) integrated with high-Q ( Q > 106) optical microdisk cavities, using an efficient (η > 90%) near-field coupling scheme based on a tapered optical fiber. Coupling of the excitonic emission is achieved by placing 1L-WSe2 in the evanescent cavity field. This preserves the microresonator high intrinsic quality factor ( Q > 106) below the bandgap of 1L-WSe2. The cavity quantum yield is QYc ≈ 10-3, consistent with operation in the broad emitter regime (i.e., the emission lifetime of 1L-WSe2 is significantly shorter than the bare cavity decay time). This scheme can serve as a precise measurement tool for the excitonic emission of layered materials into cavity modes, for both in plane and out of plane excitation

High-responsivity graphene photodetectors integrated on silicon microring resonators.

Graphene integrated photonics provides several advantages over conventional Si photonics. Single layer graphene (SLG) enables fast, broadband, and energy-efficient electro-optic modulators, optical switches and photodetectors (GPDs), and is compatible with any optical waveguide. The last major barrier to SLG-based optical receivers lies in the current GPDs' low responsivity when compared to conventional PDs. Here we overcome this by integrating a photo-thermoelectric GPD with a Si microring resonator. Under critical coupling, we achieve >90% light absorption in a ~6 μm SLG channel along a Si waveguide. Cavity-enhanced light-matter interactions cause carriers in SLG to reach ~400 K for an input power ~0.6 mW, resulting in a voltage responsivity ~90 V/W, with a receiver sensitivity enabling our GPDs to operate at a 10-9 bit-error rate, on par with mature semiconductor technology, but with a natural generation of a voltage, rather than a current, thus removing the need for transimpedance amplification, with a reduction of energy-per-bit, cost, and foot-print

Graphene-perovskite fibre photodetectors

The integration of optoelectronic devices, such as transistors and photodetectors (PDs), into wearables and textiles is of great interest for applications such as healthcare and physiological monitoring. These require flexible/wearable systems adaptable to body motions, thus materials conformable to non-planar surfaces, and able to maintain performance under mechanical distortions. Here, we prepare fibre PDs combining rolled graphene layers and photoactive perovskites. Conductive fibres ($\sim$500$\Omega$/cm) are made by rolling single layer graphene (SLG) around silica fibres, followed by deposition of a dielectric layer (Al$_{2}$O$_{3}$ and parylene C), another rolled SLG as channel, and perovskite as photoactive component. The resulting gate-tunable PDs have response time$\sim$5ms, with an external responsivity$\sim$22kA/W at 488nm for 1V bias. The external responsivity is two orders of magnitude higher and the response time one order of magnitude faster than state-of-the-art wearable fibre based PDs. Under bending at 4mm radius, up to$\sim$80\% photocurrent is maintained. Washability tests show$\sim$72\% of initial photocurrent after 30 cycles, promising for wearable applications

Chiral primary one-point functions in the D3-D7 defect conformal field theory

JHEP is an open-access journal funded by SCOAP3 and licensed under CC BY 4.0archiveprefix: arXiv primaryclass: hep-th reportnumber: NORDITA-2012-81 slaccitation: %%CITATION = ARXIV:1210.7015;%%archiveprefix: arXiv primaryclass: hep-th reportnumber: NORDITA-2012-81 slaccitation: %%CITATION = ARXIV:1210.7015;%%C.F.K. and D.Y. were supported in part by FNU through grant number 272-08-0329. G.W.S. is supported by NSERC of Canada and by the Villum foundation through their Velux Visiting Professor program

Niobium diselenide superconducting photodetectors

We report the photoresponse of niobium diselenide (NbSe2), a transition metal dichalcogenide which exhibits superconducting properties down to a single layer. Devices are built by using micromechanically cleaved 2–10 layers and tested under current bias using nano-optical mapping in the 350 mK–5K range, where they are found to be superconducting. The superconducting state can be perturbed by absorption of light, resulting in a voltage signal when the devices are current biased. The response is found to be energy dependent, making the devices useful for applications requiring energy resolution, such as bolometry, spectroscopy, and infrared imaging