Dyonic Reissner–Nordstrom black holes and superradiant stability

Black holes immersed in magnetic fields are believed to be important systems in astrophysics. One interesting topic on these systems is their superradiant stability property. In the present paper, we analytically obtain the superradiantly stable regime for the asymptotically flat dyonic Reissner–Nordstrom black holes with charged massive scalar perturbation. The effective potential experienced by the scalar perturbation in the dyonic black hole background is obtained and analyzed. It is found that the dyonic black hole is superradiantly stable in the regime $$0<r_{-}/r_{+}<2/3$$ 0 < r - / r + < 2 / 3 , where $$r_\pm $$ r ± are the event horizons of the dyonic black hole. Compared with the purely electrically charged Reissner–Nordstrom black hole case, our result indicates that the additional coupling of the charged scalar perturbation with the magnetic filed makes the black hole and scalar perturbation system more superradiantly unstable, which provides further evidence on the instability induced by magnetic field in black hole superradiance process.

Weyl consistency conditions from a local Wilsonian cutoff

A local UV cutoff $$\Lambda (x)$$ Λ ( x ) transforming under Weyl rescalings allows to construct Weyl invariant kinetic terms for scalar fields including Wilsonian cutoff functions. First we consider scalar fields in curved space-time with local bare couplings of any canonical dimension, and anomalous dimensions which describe their dependence on the UV cutoff. The local component of the UV cutoff plays the role of an additional coupling, albeit with a trivial constant $$\beta $$ β function. This approach allows to derive Weyl consistency conditions for the corresponding anomalous dimensions which assume the form of an exact gradient flow. For renormalizable theories the Weyl consistency conditions are initially of the form of an approximate gradient flow for the $$\beta $$ β functions, and we derive conditions under which it becomes the form of an exact gradient flow.

Hamiltonians for one-way quantum repeaters

Quantum information degrades over distance due to the unavoidable imperfections of the transmission channels, with loss as the leading factor. This simple fact hinders quantum communication, as it relies on propagating quantum systems. A solution to this issue is to introduce quantum repeaters at regular intervals along a lossy channel, to revive the quantum signal. In this work we study unitary one-way quantum repeaters, which do not need to perform measurements and do not require quantum memories, and are therefore considerably simpler than other schemes. We introduce and analyze two methods to construct Hamiltonians that generate a repeater interaction that can beat the fundamental repeaterless key rate bound even in the presence of an additional coupling loss, with signals that contain only a handful of photons. The natural evolution of this work will be to approximate a repeater interaction by combining simple optical elements.

Influence of bulk incorporation of FDAc and PTX on polymer properties

In the last decades PLLA-based copolymers have been among the most attractive polymeric candidates used to fabricate devices for drug delivery and stent applications in the cardiovascular system. PLLA is biocompatible and biodegradable, exhibits a wide range of erosion times and has tunable mechanical properties. Therefore, the influence of drug incorporation on the physicochemical properties of biodegradable PLLA copolymers were examined in this study using Fluorescein diacetate (FDAc) and Paclitaxel (PTX). A percental amount of these drugs (17.5 %) were incorporated into poly(L-lactide-co-glycolide) (P(LLA-co-GA)) and poly(L-lactide-co-ε-caprolactone) (P(LLA-co-CL)) made via spray coating. The polymer surface properties, such as surface morphology and hydrophilicity were also examined and remained rather unchanged for both polymers after drug loadings. Furthermore, also the contact angle changed rather marginally. However, both polymers have already different thermal properties without the drug embedded, especially the glass transition temperature (TG) is for P(LLA-co-CL) under 37°C and for P(LLA-co-GA) considerable above with around 66°C. An rather high increase in TG achieved by addition of FDAc or PTX, crucial influences the drug release profiles for P(LLA-co-CL) in contrast to P(LLA-co-GA). Besides these results preliminarily experiments of additional coupling of other drugs on the polymer surface were performed and we obtained an influence of FDAc or PTX. The drug incorporation and physicochemical characterization data obtained in this study is relevant in optimizing the incorporation or coupling of further drugs on the polymer surface and delivery properties of these potential multi drug delivery coatings.

The influence of organosoluble (co)polyimides side functionalization and drawing parameters on the optical fibre coatings formation and properties

A series of the copolyimides have been synthesized by one-step high-temperature method in m-cresol solution to explore their effect on the optical fibre coatings formation and properties. The following parameters that influence the coating quality and properties have been estimated: the viscosity of the polymer solution, drawing technological parameters, polyimide (PI) structure and molecular weight. It was found that copolyimides bearing side hydroxyl and carboxyl groups formulate the coatings with good adhesion without additional coupling agent. The fibres with elaborated PI coatings have high thermal stability. For some of them, 20% reduction of the fibre’s bending strength takes place only after heating for 24–72 h at 300°C.

New Configuration of Handset MIMO Antenna for LTE 700 Band Applications

A compact handset multiple-input multiple-output (MIMO) antenna for long-term evolution (LTE) 700 band (746~787 MHz) applications is proposed. The proposed antenna consists of two symmetrical PIFAs. Without the usage of any additional coupling elements between closely mounted antennas, a high isolation (>15 dB) and a low enveloped correlation coefficient (ECC<0.35) are achieved by the optimum location and arrangement of MIMO antenna elements.

Novel Compact Multiband MIMO Antenna for Mobile Terminal

A novel compact MIMO antenna for personal digital assistant (PDA) and pad computer is proposed. The proposed antenna is composed by two multipatch monopole antennas which are placed 90° apart for orthogonal radiation. To strengthen the isolation, a T-shaped ground branch with proper dimension is used to generate an additional coupling path to lower the mutual coupling (below −15 dB), especially at GSM850/900 band. The proposed MIMO antenna is fabricated and tested, both the simulated and the measured results are presented, and some parametric studies are also demonstrated. In addition, there are some advantages about the proposed antenna such as simple structure, easy fabrication, and low cost.