Subharmonic fidelity revival in a driven PXP model

The PXP model hosts a special set of nonergodic states, referred to as quantum many-body scars. One of the consequences of quantum scarring is the periodic revival of the wave function fidelity. It has been reported that quantum fidelity revival occurs in the PXP model for certain product states, and periodic driving of chemical potential can enhance the magnitude of quantum revival, and can even change the frequencies of revival showing the subharmonic response. Although the effect of the periodic driving in the PXP model has been studied in the limit of certain perturbative regimes, the general mechanism of such enhanced revival and frequency change has been barely studied. In this work, we investigate how periodic driving in the PXP model can systematically control the fidelity revival. Particularly, focusing on the product state so called a Neel state, we analyze the condition of driving to enhance the magnitude of revival or change the frequencies of revival. To clarify the reason of such control, we consider the similarities between the PXP model and the free spin-1/2 model in graph theoretical analysis, and show that the quantum fidelity feature in the PXP model is well explained by the free spin-1/2 model. In addition, under certain limit of the driving parameters, analytic approach to explain the main features of the fidelity revival is also performed. Our results give an insight of the scarring nature of the periodically driven PXP model and pave the way to understand their (sub-)harmonic responses and controls.Comment: 7 pages, 3 figure

Controllable Skyrmion Islands in a Moir\'e Magnet

Antiferromagnetic(AFM) skyrmions have been in the spotlight as ideal topological magnetic bits. Although they are topologically protected, they do not exhibit the skyrmion Hall effect unlike the ferromagnetic ones. Thus, AFM skyrmions are considered to provide a better control of the skyrmion's motion due to the absence of the skyrmion Magnus effect. In this work, we propose a possible realization of controllable AFM skyrmions in a twisted Moir\'e magnet. The tunability of Moir\'e materials is not only a good platform for the provision of rich phases, but also for the stabilization of skyrmion phase. We investigate the ground state of twisted bilayer AFM system by solving the Landau-Lifshitz-Gilbert equation in a continuum model. We show that the AFM skyrmions are stabilized even in the absence of the external/dipolar magnetic field, as a consequence of the interplay of interlayer coupling, Dzyaloshinskii-Moriya (DM) interaction and Ising anisotropy. More interestingly, due to the magnetoelectric effect, the application of an external electric field locally stabilizes the skyrmions in the twisted bilayer AFM systems, even in the absence of DM interaction. It also allows the skyrmion helicity to change continuously when both the DM interaction and an electric field are present. We show the phase diagram with respect to the strength of interlayer coupling, the DM interaction and an electric field. Our results suggest the possibility of using AFM skyrmions as stable, controllable topological magnetic bits

Physicochemical and Biological Properties of Land and Water Bodies Surrounding Major Dumpsites in Kolkata

In this paper we have investigated the data acquired from the analysis of the soil and water samples from and around the dump sites in Kolkata and North 24 Paragana district of West Bengal where the population density is extremely high. The treatment of disposal of municipal solid wastes and waste water has been inadequate to negligible in these areas and as a result the quality of soil and water bodies is subject to deterioration. We have made use of GPS enabled Satellite acquired images and its associated softwares to identify and demarcate the areas that come under the direct impact of the dumping sites, and which ultimately are the areas prone to diseases and degradation in the coming years. The pH, salinity, Total Dissolved Solvents and oxidation reduction potential has been investigated for the basic characterization of the samples. An estimate of heavy metals has also been made. Estimation of salts and oxides from the various sediments and soil samples were acquired. Identification of bacteria, under the purview of biological studies and the dependence of their growth on physiochemical parameters of the surrounding has portrayed an alarming result.  Adjacent to these areas there are agricultural fields where leached water from the dumping site directly drain into and cause biomagnifications. Contamination of the ground water is also sizable. This research will help to control pollution and biological outbreaks as well as suggest areas where immediate care should be taken to set up environmental restoration. The findings of the paper will further enlighten the planning and designing of waste disposal in urban areas and assist in its policy making in urban areas and thereby improve the quality of life of the scavengers who are left to equate their survival with the garbage mounds

Underwater acoustic records from the March 2009 eruption of Hunga Ha'apai-Hunga Tonga volcano in the Kingdom of Tonga

A network of autonomous underwater hydrophones is used to monitor acoustic activity associated with Hunga Ha'apai-Hunga Tonga volcano during a period of 15 months. The data provide a continuous record spanning a surtseyan eruption (VEI 2) in March of 2009, which input ~10¹³ J of acoustic energy into the ocean soundscape. In the months before the eruption, the volcano can be identified as an intermittent source of ambient noise. The period of seismic unrest that precedes the eruption begins at 15:11 UTC on 16 March (04:11 LT on 17 March), approximately 7 h before the first satellite confirmation of eruptive activity and 14 h before the first eyewitness reports. The initial seismic activity, which includes a single 4.8 m[subscript b] event at 15:25, evolves as a typical foreshock-mainshock-aftershock sequence. By 15:38, however, the rate of small earthquakes begins to increase, marking the onset of the seismic swarm. The period of highest-amplitude acoustic energy release between 16:40 and ~17:10 is interpreted to mark the opening of the volcanic conduit. By 19:00 on 16 March, the acoustic signature of the volcano is marked by a continuous wide-band (1-20 Hz) noise and a set of transient very-broadband (1-125 Hz) explosion signals. This activity is characteristic of the main surtseyan phase of the eruption. Both the intensity of explosions and the amplitude of the lower frequency wide-band noise decay through time, and eruptive activity likely ends at ~09:00 on 19 March, ~2.7 days after the initiation of seismic activity. At this time the continuous low frequency noise decays to near back-ground levels and signal coherence drops suddenly. Low-level acoustic unrest persists through June of 2009, after which the volcano becomes acoustically dormant during the remaining ten months of monitoring. The analysis of volcano-acoustic signals associated with Hunga Ha'apai-Hunga Tonga volcano highlights the potential role of regional hydroacoustic monitoring in assessing volcanic hazards in arc settings. (C) 2012 Elsevier B.V. All rights reserved.This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.elsevier.com/Keywords: Acoustics, Arc volcanism, Hydrophone monitoring, Hunga Ha'apai-Hunga Tonga Volcano, Surtseyan eruptionKeywords: Acoustics, Arc volcanism, Hydrophone monitoring, Hunga Ha'apai-Hunga Tonga Volcano, Surtseyan eruptio

Antarctic icebergs: A significant natural ocean sound source in the Southern Hemisphere

In late 2007, two massive icebergs, C19a and B15a, drifted into open water and slowly disintegrated in the southernmost Pacific Ocean. Archived acoustic records show that the high-intensity underwater sounds accompanying this breakup increased ocean noise levels at mid-to-equatorial latitudes over a period of ~1.5 years. More typically, seasonal variations in ocean noise, which are characterized by austral summer-highs and winter-lows, appear to be modulated by the annual cycle of Antarctic iceberg drift and subsequent disintegration. This seasonal pattern is observed in all three Oceans of the Southern Hemisphere. The life cycle of Antarctic icebergs affects not only marine ecosystem but also the sound environment in far-reaching areas and must be accounted for in any effort to isolate anthropogenic or climate-induced noise contributions to the ocean soundscape.Keywords: Trend, Seasonality, Antarctica, Ocean noise, Iceber

Genetic analysis of typical wet-type age-related macular degeneration and polypoidal choroidal vasculopathy in Japanese population

Age-related macular degeneration (AMD) is a common cause of blindness in the elderly. Caucasian patients are predominantly affected by the dry form of AMD, whereas Japanese patients have predominantly the wet form of AMD and/or polypoidal choroidal vasculopathy (PCV). Although genetic association in the 10q26 (ARMS2/HTRA1) region has been established in many ethnic groups for dry-type AMD, typical wet-type AMD, and PCV, the contribution of the 1q32 (CFH) region seem to differ among these groups. Here we show a single nucleotide polymorphism (SNP) in the ARMS2/HTRA1 locus is associated in the whole genome for Japanese typical wet-type AMD (rs10490924: \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p = 4.1 \times 10 ^{ - 4}$$\end{document}, OR = 4.16) and PCV (rs10490924: \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p = 3.7 \times 10 ^{ -8}$$\end{document}, OR = 2.72) followed by CFH (rs800292: \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p = 7.4 \times 10 ^{ -5}$$\end{document}, OR = 2.08; \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p = 2.6 \times {10^{ - 4}}$$\end{document}, OR = 2.00), which differs from previous studies in Caucasian populations. Moreover, a SNP (rs2241394) in complement component C3 gene showed significant association with PCV (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p = 2.5 \times {10^{ - 3}}$$\end{document}, OR = 3.47). We conclude that dry-type AMD, typical wet-type AMD, and PCV have both common and distinct genetic risks that become apparent when comparing Japanese versus Caucasian populations

Spin-helix-driven insulating phase in two-dimensional lattice

Motivated by emergent SU(2) symmetry in the spin-orbit-coupled system, we study the spin-helix-driven insulating phase in a two-dimensional lattice. When both Rashba and Dresselhaus spin-orbit couplings are present, the perfect Fermi-surface nesting occurs at a special condition depending on the lattice geometry. In this case, the energies of spin up at any wave vector k[over ⃗] are equivalent to the ones of spin down at k[over ⃗]+Q[over ⃗] with the shifting wave vector Q[over ⃗]. Thus, the system stabilizes the magnetic insulator with spiral-like magnetic ordering even in the presence of tiny electron-electron interaction where the magnetic ordering wave vector is proportional to Q[over ⃗]. We first show the condition for the existence of the shifting wave vector in a general lattice model and emergent SU(2) symmetry in the spin-orbit-coupled system. Then, we exemplify this in a square lattice at half filling and discuss the insulating phase with (non)coplanar spin density wave and charge order. Our study emphasizes different possible types of two-dimensional magnetic materials that can be applicable to various van der Waals materials and their heterostructures with the control of electric field, strain, and pressure

Controllable Floquet edge modes in a multi-frequency driving system

A driven quantum system has been recently studied in the context of nonequilibrium phase transitions and their responses. In particular, for a periodically driven system, its dynamics are described in terms of the multi-dimensional Floquet lattice with a lattice size depending on number of driving frequencies and their rational or irrational ratio. So far, for a multi-frequency driving system, the energy pumping between the sources of frequencies has been widely discussed as a signature of topologically nontrivial Floquet bands. However, the unique edge modes emerging in the Floquet lattice has not been explored yet. Here, we discuss how the edge modes in the Floquet lattice are controlled and result in the localization at particular frequencies, when multiple frequencies are present and their magnitudes are commensurate values. First, we construct the minimal model to exemplify our argument, focusing on a two-level system with two driving frequencies. For strong frequency limit, one can describe the system as a quasi-one dimensional Floquet lattice where the effective hopping between the neighboring sites depends on the relative magnitudes of potential for two frequency modes. With multiple driving modes, there always exist the non-trivial Floquet lattice boundaries via controlling the frequencies and this gives rise to the states that are mostly localized at such Floquet lattice boundaries, i.e. particular frequencies. We suggest the time-dependent Creutz ladder model as a realization of our theoretical Hamiltonian and show the emergence of controllable Floquet edge modes

Tracking beaked whales with a passive acoustic profiler float

Acoustic methods are frequently used to monitor endangered marine mammal species. Advantages of acoustic methods over visual ones include the ability to detect submerged animals, to work at night, and to work in any weather conditions. A relatively inexpensive and easy-to-use acoustic float, the QUEphone, was developed by converting a commercially available profiler float to a mobile platform, adding acoustic capability, and installing the ERMA cetacean click detection algorithm of Klinck and Mellinger [(2011). J. Acoust. Soc. Am. 129(4), 1807-1812] running on a high-power DSP. The QUEphone was tested at detecting Blainville's beaked whales at the Atlantic Undersea Test and Evaluation Center (AUTEC), a Navy acoustic test range in the Bahamas, in June 2010. Beaked whale were present at AUTEC, and the performance of the QUEphone was compared with the Navy's Marine Mammal Monitoring on Navy Ranges (M3R) system. The field tests provided data useful to evaluate the QUEphone's operational capability as a tool to detect beaked whales and report their presence in near-real time. The range tests demonstrated that the QUEphone's beaked whale detections were comparable to that of M3R's, and that the float is effective at detecting beaked whales. (C) 2013 Acoustical Society of America. [http://dx.doi.org/10.1121/1.4773260]Keywords: Ambient noise, Ocean, Ziphius cavirostris, Echolocation clicks, Mesoplodon densirostri

Ocean sound levels in the northeast Pacific recorded from an autonomous underwater glider.

Ocean gliders are a quiet and efficient mobile autonomous platform for passive acoustic monitoring and oceanographic measurements in remote marine environments. During July 20-August 6 2012, we used a Teledyne Webb Research Slocum G2 glider equipped with a hydrophone logging system to record ocean sound along a 458 km north to south traverse of the outer continental shelf break along the U.S. Pacific Northwest coast. Glider derived recordings yielded a unique perspective on the variation of ambient sound with depth, where natural wind generated surface processes were identified as a dominant acoustic contributor to spectral levels in the region. Near and far-field vessel radiated noise were also found to add significant energy to ambient conditions. Spatially distributed measurements of ambient sound levels recorded from the glider were consistent with long-term spectral estimates from fixed station, deep ocean hydrophone array measurements during the 1990-2000's in the region. Ocean sound level measurements captured by a mobile glider are shown to be an effective and valuable asset for describing ocean surface wind conditions and characterizing spatial and temporal changes in the underwater acoustic environment over a broad regional scale