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Black holes

Masahiro Hotta, Yasusada Nambu, Koji Yamaguchi
We propose a model with multiple qubits that reproduces the thermal properties of four-dimensional Schwarzschild black holes (BHs) by simultaneously taking account of the emission of Hawking particles and the zero-energy soft-hair evaporation at the horizon. The results verify that the entanglement entropy between a qubit and other subsystems, including emitted radiation, is much larger than the BH entropy analogue of the qubit, as opposed to the Page curve prediction. Our result suggests that early Hawking radiation is entangled with soft hair and that late Hawking radiation can be highly entangled with the degrees of freedom of a BH, avoiding the emergence of a firewall at the horizon...
May 4, 2018: Physical Review Letters
Min-Hye Jeong, Dohyun Kwak, Hyun-Soo Ra, A-Young Lee, Jong-Soo Lee
Few-layer black phosphorus has shown great potential for next-generation electronics with tunable band gap and high carrier mobility. For the electronic applications, the thickness modulation of a BP flake is an essential due to its thickness-dependent electronic properties. However, controlling the precise thickness of few-layer BP is a challenge for the high-performance device applications. In this study, we demonstrate that thermal treatment under ambient condition precisely controls the thickness of BP flake...
May 17, 2018: ACS Applied Materials & Interfaces
Imran Ali, Omar M L Alharbi, Zeid A Alothman, Ahmad Yacine Badjah
Titanium oxide nanoparticles were doped with copper and characterized by XRD, FT-IR, TEM and SEM. The surface morphology was spherical with 15-26 nm as particle size. The doped titanium oxide (Co/TiO2 ) nanomaterial was used for photodegradation of amido black dye in water. The maximum photodegradation of amido black obtained was 90%. The values of free energy, and enthalpy were negative, indicating spontaneous photodegradation of amido black dye. The photodegradation of amido black dye obeyed first order kinetic model...
May 16, 2018: Photochemistry and Photobiology
Lionel London, Sebastian Khan, Edward Fauchon-Jones, Cecilio García, Mark Hannam, Sascha Husa, Xisco Jiménez-Forteza, Chinmay Kalaghatgi, Frank Ohme, Francesco Pannarale
Gravitational-wave observations of binary black holes currently rely on theoretical models that predict the dominant multipoles (ℓ=2,|m|=2) of the radiation during inspiral, merger, and ringdown. We introduce a simple method to include the subdominant multipoles to binary black hole gravitational waveforms, given a frequency-domain model for the dominant multipoles. The amplitude and phase of the original model are appropriately stretched and rescaled using post-Newtonian results (for the inspiral), perturbation theory (for the ringdown), and a smooth transition between the two...
April 20, 2018: Physical Review Letters
J S Pedernales, M Beau, S M Pittman, I L Egusquiza, L Lamata, E Solano, A Del Campo
We introduce an exact mapping between the Dirac equation in (1+1)-dimensional curved spacetime (DCS) and a multiphoton quantum Rabi model (QRM). A background of a (1+1)-dimensional black hole requires a QRM with one- and two-photon terms that can be implemented in a trapped ion for the quantum simulation of Dirac particles in curved spacetime. We illustrate our proposal with a numerical analysis of the free fall of a Dirac particle into a (1+1)-dimensional black hole, and find that the Zitterbewegung effect, measurable via the oscillatory trajectory of the Dirac particle, persists in the presence of gravity...
April 20, 2018: Physical Review Letters
Carl L Rodriguez, Pau Amaro-Seoane, Sourav Chatterjee, Frederic A Rasio
We present models of realistic globular clusters with post-Newtonian dynamics for black holes. By modeling the relativistic accelerations and gravitational-wave emission in isolated binaries and during three- and four-body encounters, we find that nearly half of all binary black hole mergers occur inside the cluster, with about 10% of those mergers entering the LIGO/Virgo band with eccentricities greater than 0.1. In-cluster mergers lead to the birth of a second generation of black holes with larger masses and high spins, which, depending on the black hole natal spins, can sometimes be retained in the cluster and merge again...
April 13, 2018: Physical Review Letters
Bogdan Ganchev, Jorge E Santos
We present a numerical analysis of the stability properties of the black holes with scalar hair constructed by Herdeiro and Radu. We prove the existence of a novel gauge where the scalar field perturbations decouple from the metric perturbations, and analyze the resulting quasinormal mode spectrum. We find unstable modes with characteristic growth rates which for uniformly small hair are almost identical to those of a massive scalar field on a fixed Kerr background.
April 27, 2018: Physical Review Letters
Joshua Sokol
No abstract text is available yet for this article.
May 11, 2018: Science
Haruo Imagawa, Xiaoyong Wu, Hiroshi Itahara, Shu Yin, Kazunobu Kojima, Shigefusa F Chichibu, Tsugio Sato
Ca-Bridged siloxenes (Ca-siloxenes) composed of two-dimensional siloxene planes with Ca bridging were prepared and their photocatalytic properties for nitrogen oxide (NO) removal were investigated. Ca-Siloxenes were synthesized via a solid-state metathesis reaction using TaCl5 to extract Ca from CaSi2 with different Cl2/Ca molar ratios of 0.25, 1.25 and 2.5 (CS0.25, CS1.25 and CS2.5, respectively) in an attempt to control the extent of Ca extraction. Ca-Siloxenes have a wide optical absorption band from the visible to ultraviolet region with absorption edges of 1...
May 10, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Xiaolong Chen, Chen Chen, Adi Levi, Lothar Houben, Bingchen Deng, Shaofan Yuan, Chao Ma, Kenji Watanabe, Takashi Taniguchi, Doron Naveh, Xu Du, Fengnian Xia
A high saturation velocity semiconductor is appealing for applications in electronics and optoelectronics. Thin-film black phosphorus (BP), an emerging layered semiconductor, shows a high carrier mobility and strong mid-infrared photoresponse at room temperature. Here, we report the observation of high intrinsic saturation velocity in 7 to 11 nm thick BP for both electrons and holes as a function of charge-carrier density, temperature, and crystalline direction. We distinguish a drift velocity transition point due to the competition between the electron-impurity and electron-phonon scatterings...
May 1, 2018: ACS Nano
Jun Zheng, Zhiyuan Yu, Rui Guo, Hao Li, Chao You, Lu Ma
OBJECTIVE: Hematoma expansion is significantly related to unfavorable prognosis in intracerebral hemorrhage (ICH). The black hole sign is a novel marker on non-contrast computed tomography for predicting hematoma expansion. However, its predictive values are different in previous studies. Thus, this meta-analysis was conducted to evaluate the predictive significance of the black hole sign for hematoma expansion in ICH. METHODS: Literature search was performed systematically...
April 27, 2018: World Neurosurgery
Xiaoxia Han, Ju Huang, Xiangxiang Jing, Dayan Yang, Han Lin, Zhigang Wang, Pan Li, Yu Chen
The conventional inorganic semiconductors are not suitable for in vivo therapeutic nanomedicine because of the lack of an adequate and safe irradiation source to activate them. This work reports on the rational design of titania (TiO2 )-based semiconductors for enhanced and synergistic sono-/photoinduced tumor eradication by creating an oxygen-deficient TiO2- x layer onto the surface of TiO2 nanocrystals, which can create a crystalline-disordered core/shell structure (TiO2 @TiO2- x ) with black color. As found in the lessons from traditional photocatalysis, such an oxygen-deficient TiO2- x layer with abundant oxygen defects facilitates and enhances the separation of electrons (e- ) and holes (h+ ) from the energy-band structure upon external ultrasound irradiation, which can significantly improve the efficacy of sono-triggered sonocatalytic tumor therapy...
April 30, 2018: ACS Nano
G Antoniou, A Bakopoulos, P Kanti
We consider a general Einstein-scalar-Gauss-Bonnet theory with a coupling function f(ϕ). We demonstrate that black-hole solutions appear as a generic feature of this theory since a regular horizon and an asymptotically flat solution may be easily constructed under mild assumptions for f(ϕ). We show that the existing no-hair theorems are easily evaded, and a large number of regular black-hole solutions with scalar hair are then presented for a plethora of coupling functions f(ϕ).
March 30, 2018: Physical Review Letters
Hector O Silva, Jeremy Sakstein, Leonardo Gualtieri, Thomas P Sotiriou, Emanuele Berti
We identify a class of scalar-tensor theories with coupling between the scalar and the Gauss-Bonnet invariant that exhibit spontaneous scalarization for both black holes and compact stars. In particular, these theories formally admit all of the stationary solutions of general relativity, but these are not dynamically preferred if certain conditions are satisfied. Remarkably, black holes exhibit scalarization if their mass lies within one of many narrow bands. We find evidence that scalarization can occur in neutron stars as well...
March 30, 2018: Physical Review Letters
Daniela D Doneva, Stoytcho S Yazadjiev
In the present Letter, we consider a class of extended scalar-tensor-Gauss-Bonnet (ESTGB) theories for which the scalar degree of freedom is excited only in the extreme curvature regime. We show that in the mentioned class of ESTGB theories there exist new black-hole solutions that are formed by spontaneous scalarization of the Schwarzschild black holes in the extreme curvature regime. In this regime, below certain mass, the Schwarzschild solution becomes unstable and a new branch of solutions with a nontrivial scalar field bifurcates from the Schwarzschild one...
March 30, 2018: Physical Review Letters
Hunter Gabbard, Michael Williams, Fergus Hayes, Chris Messenger
We report on the construction of a deep convolutional neural network that can reproduce the sensitivity of a matched-filtering search for binary black hole gravitational-wave signals. The standard method for the detection of well-modeled transient gravitational-wave signals is matched filtering. We use only whitened time series of measured gravitational-wave strain as an input, and we train and test on simulated binary black hole signals in synthetic Gaussian noise representative of Advanced LIGO sensitivity...
April 6, 2018: Physical Review Letters
Hang Yu, Denis Martynov, Salvatore Vitale, Matthew Evans, David Shoemaker, Bryan Barr, Giles Hammond, Stefan Hild, James Hough, Sabina Huttner, Sheila Rowan, Borja Sorazu, Ludovico Carbone, Andreas Freise, Conor Mow-Lowry, Katherine L Dooley, Paul Fulda, Hartmut Grote, Daniel Sigg
We propose an upgrade to Advanced LIGO (aLIGO), named LIGO-LF, that focuses on improving the sensitivity in the 5-30 Hz low-frequency band, and we explore the upgrade's astrophysical applications. We present a comprehensive study of the detector's technical noises and show that with technologies currently under development, such as interferometrically sensed seismometers and balanced-homodyne readout, LIGO-LF can reach the fundamental limits set by quantum and thermal noises down to 5 Hz. These technologies are also directly applicable to the future generation of detectors...
April 6, 2018: Physical Review Letters
J R Espinosa, D Racco, A Riotto
For the current central values of the Higgs boson and top quark masses, the standard model Higgs potential develops an instability at a scale of the order of 10^{11}  GeV. We show that a cosmological signature of such instability could be dark matter in the form of primordial black holes seeded by Higgs fluctuations during inflation. The existence of dark matter might not require physics beyond the standard model.
March 23, 2018: Physical Review Letters
Xiaoyu Xuan, Zhuhua Zhang, Wanlin Guo
Two-dimensional (2D) black phosphorus (BP) has attracted broad interests but remains to be synthesized. One of the issues lies in its large number of 2D allotropes with highly degenerate energies, especially 2D blue phosphorus. Here, we show that both nitrogen and hole-carrier doping can lift the energy degeneracy and locate 2D BP in a deep global energy minimum, while arsenic doping favours the formation of 2D blue phosphorus, attributed to a delicate interplay between s-p overlapping and repulsion of lone pairs...
April 23, 2018: Nanoscale
Virginie Monnet-Corti, Angeline Antezack, Marion Pignoly
INTRODUCTION: Smile aesthetics is based on numerical, physical, physiological and psychological data regarding beauty, while taking into account the desires of the patient. It is determined by the shape, colour and position of the lips, teeth and gingival tissues. Periodontal examination in both the facial and labial settings supports analysis of the gingival display during natural and forced smiling, the health of the periodontium, the gingival contours, the aesthetic gingival line, and the presence of the papillae...
March 2018: L' Orthodontie Française
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