Anomalous State Research Articles

Coherent quantum transport in a transitionmetal dichalcogenides superconducting double junction with Rashba spin-orbit interaction

In this study, the coherent quantum transport problem in a transitionmetal dichalcogenides superconducting double junctions with the Rashba spin-orbit interaction has been investigated. It is found that the coherent tunneling conductance is characterized by the nontrivial Rashba metallic states which can be achieved by tuning the Rashba spin-orbit interaction and Fermi energy. Remarkably, the hump structure and the reentrant behavior of the coherent tunneling conductances can be served as a promising option to detect the Rashba ring metal state, the normal Rashba metal state and the anomalous Rashba metal state. Since the retro-normal reflection and the specular Andreev reflection occur in the Rashba ring metal state, we thus expect that it can also offer a potential route to detect the retro-normal reflection and the specular Andreev reflection based on the transitionmetal dichalcogenides based superconducting double junctions.

New classes of topological crystalline insulators having surface rotation anomaly.

We discover new types of quantum anomalies in two-dimensional systems with time-reversal symmetry (T) and discrete rotation symmetry with order of n = 2, 4, and 6 (Cn ). The new anomalous states have n flavors of massless Dirac fermions protected by T and Cn , whereas any two-dimensional lattices having the two symmetries must have a multiple of 4, 8, and 12 Dirac cones for n = 2, 4, and 6, respectively. We show that these anomalous states are physically realized on the surface of new classes of topological crystalline insulators, normal to the rotation axis. Moreover, these topological crystalline insulators support n gapless one-dimensional helical mode on the otherwise fully gapped side surface, connecting the anomalous two-dimensional states on the top and bottom surfaces. The presence of these helical modes enables a new quantum device made from a topological crystalline insulator nanorod, a "helical nanorod," which has a quantized longitudinal conductance of ne 2/h.

Retro-normal reflection and specular Andreev reflection in a transition metal dichalcogenides superconducting heterojunction

Based on the Bogoliubov-de Gennes equation, the spin-resolved scattering problem through a transition metal dichalcogenides normal metal/superconductor has been investigated. It is shown that the tunneling conductances have a close relationship with the nontrivial Rashba metallic states. Without the Rashba spin–orbit interaction (RSOI), the tunneling conductances exhibit clear characteristic features for detecting the normal Rashba metal state (NRMS) and the anomalous Rashba metal state (ARMS). While in the presence of RSOI, the oscillation, hump structure, and the reentrant behavior of the tunneling conductances can be served as a smoking gun to distinguish the Rashba ring metal state (RRMS) from those nontrivial metallic states. Fundamentally, in sharp contrast to the NRMS and the ARMS where only the normal reflection and the retro-Andreev reflection can occur, the additional scattering processes of the retro-normal reflection (RNR) and the specular Andreev reflection (SAR) can take place in the present junction with the RRMS. Thus the obtained results offer a feasible way to determine the RNR, the SAR, and the nontrivial Rashba metallic states based on the transition metal dichalcogenides superconducting heterojunction.

Anomalous phase shift in a Josephson junction via an antiferromagnetic interlayer

The anomalous ground state phase shift in S/AF/S Josephson junctions in the presence of the Rashba SO-coupling is predicted and numerically investigated. It is found to be a consequence of the uncompensated magnetic moment at the S/AF interfaces. The anomalous phase shift exhibits a strong dependence on the value of the SO-coupling and the sublattice magnetization with the simultaneous existence of stable and metastable branches. It depends strongly on the orientation of the Neel vector with respect to the S/AF interfaces via the dependence on the orientation of the interface uncompensated magnetic moment, what opens a way to control the Neel vector by supercurrent in Josephson systems.

Quickest Detection of Intermittent Signals With Application to Vision-Based Aircraft Detection

In this brief, we consider the problem of quickly detecting changes in an intermittent signal that can (repeatedly) switch between a normal and an anomalous state. We pose this intermittent signal detection (ISD) problem as an optimal stopping problem and establish a quickest ISD rule with a threshold structure. We develop bounds to characterize the performance of our ISD rule and establish a new filter for estimating its detection delays. Finally, we examine the performance of our ISD rule in both a simulation study and an important vision-based aircraft detection application where the ISD rule demonstrates improvements in detection range and false alarm rates relative to the current state-of-the-art aircraft detection techniques.

Space-time phononic crystals with anomalous topological edge states

It is well known that an interface created by two topologically distinct structures could host nontrivial edge states that are immune to defects. In this letter, we introduce a one-dimensional space-time phononic crystal and study the associated anomalous topological edge states. A space-decoupled time modulation is assumed. While preserving the key topological feature of the system, such a modulation also duplicates the edge state mode across the spectrum, both inside and outside the band gap. It is shown that, in contrast to conventional topological edge states which are excited by frequencies in the Bragg regime, the time-modulation-induced frequency conversion can be leveraged to access topological edge states at a deep subwavelength scale where the entire phononic crystal size is merely 1/5.1 of the wavelength. This remarkable feature could open a new route for designing miniature devices that are based on topological physics.

The Role of Clouds and Surface Heat Fluxes in the Maintenance of the 2013–2016 Northeast Pacific Marine Heatwave

AbstractStarting in late 2013, the Northeast (NE) Pacific Ocean experienced anomalously warm sea surface temperatures (SSTs) that persisted for over 2 years. This marine heatwave, known as “the Blob,” produced many devastating ecological impacts with socioeconomic implications for coastal communities. The warm waters observed during the NE Pacific 2013/2016 marine heatwave altered the surface energy balance and disrupted ocean–atmosphere interactions in the region. In principle, ocean–atmosphere interactions following the formation of the marine heatwave could have perpetuated warm SSTs through a positive SST‐cloud feedback. The actual situation was more complicated. While reanalysis data show a decrease in boundary layer cloud fraction and an increase in downward shortwave radiative flux at the surface coincident with warm SSTs, this was accompanied by an increase in longwave radiative fluxes at the surface, as well as an increase in sensible and latent heat fluxes out of the ocean mixed layer. The result is a small negative net heat flux anomaly (compared to the anomalies of the individual terms contributing to the net heat flux). This provides new information about the midlatitude ocean–atmosphere system while it was in a perturbed state. More specifically, a mixed layer heat budget reveals that anomalies in both the atmospheric and oceanic processes offset each other such that the anomalously warm SSTs persisted for multiple years. The results show how the atmosphere–ocean system in the NE Pacific is able to maintain itself in an anomalous state for an extended period of time.

Stratospheric modulation of the large‐scale circulation in the Atlantic–European region and its implications for surface weather events

AbstractExtreme states of the stratospheric polar vortex can have long‐lasting impacts on extratropical circulation patterns, such as the North Atlantic Oscillation (NAO). This provides windows of subseasonal predictability beyond the typical weather forecast horizon of about 10 days. Subseasonal forecasts of surface weather are of significant interest in weather‐dependent socio‐economic sectors. For example, demand and supply for electricity and gas are weather dependent and therefore accurate forecasts are important for the energy industry and energy trading. Here we investigate the subseasonal impact of stratospheric conditions on surface weather events relevant to the energy industry in five subregions of Europe in winter. We use a definition of seven Atlantic–European weather regimes to describe the variability of the large‐scale circulation on subseasonal time scales. Results indicate that weather events are often associated with more than one preferred weather regime. In turn, some weather regimes project onto a specific NAO phase, while others are independent of the NAO. As expected, anomalous stratospheric polar vortex states predominantly modulate the occurrence of regimes related to the NAO and affect the likelihood of their associated weather events. In contrast, the occurrence of weather regimes which do not project well onto the NAO is not affected by anomalous stratospheric polar vortex states. These regimes provide pathways to unexpected weather events in extreme stratospheric polar vortex states. For example, weak stratospheric polar vortex states enhance the likelihood of negative NAO. High wind events in Central Europe predominantly occur during the zonal regime, strongly projecting onto positive NAO. However, these events also occur during the Atlantic trough regime, which is unaffected by anomalous stratospheric polar vortex states and thus provides a pathway to Central European high wind events during weak stratospheric polar vortex states. A correct NAO prediction alone is therefore not sufficient to correctly predict surface weather after extreme stratospheric polar vortex states. Moreover, weather regime life cycles independent of the NAO also need to be forecast accurately.

El Niño–East Asian monsoon teleconnection and its diversity in CMIP5 models

In this study, we assess the performance of state-of-the-art coupled models in reproducing El Nino diversity and its impacts on the East Asian Summer Monsoon (EASM), based on simulations taken from the Coupled Model Intercomparison Project phase 5 (CMIP5). All of the 17 models used in this study are identified to give reasonable eastern-Pacific (EP) El Nino-related sea surface temperature anomalies (SSTA) and anomalous Walker circulation compared with observations, whereas one-third of the models fail to reproduce the Walker circulation anomalies for central-Pacific (CP) El Nino. In these models, negative SSTA over the eastern-to-central Pacific are found to be too strong, while positive SSTA shift to the western Pacific during CP El Nino. There is thus sinking (rising) motion over the central (western) part of the Pacific basin, implying westward displaced anomalous Walker cells, relative to the observed. This results in simulated low-level cyclonic flow and positive rainfall anomalies over the far western north Pacific/South China Sea during and after the peak phase of CP El Nino, which are opposite to the observed anomalous climate state. The other two-thirds of models, with realistic CP El Nino-related anomalous Walker cell, can better reproduce the corresponding wind circulation and rainfall anomalies over East Asian (EA) region. The contrasting CP El Nino-related teleconnection among models mainly arises from the different simulated CP El Nino SSTA, which in turn determine the circulation anomalies through a Gill-type response. Further analyses reveal that, in the mean state of models with erroneous teleconnection, there exists a large cold SST bias over the eastern Pacific. The stronger Walker circulation, and possibly the stronger Bjerknes feedback, might be responsible for the overly negative SSTA associated with CP El Nino in the vicinity. Our results highlight the sensitivity of El Nino–EA climate linkage to the oceanic state in models, especially for CP El Nino events.

Volatile memory analysis using the MinHash method for efficient and secured detection of malware in private cloud

Today, most organizations employ cloud computing environments for both computational reasons and for storing their critical files and data. Virtual servers are an example of widely used virtual resources provided by cloud computing architecture. Therefore, virtual servers are considered an attractive target for cyber-attackers, who launch their attacks by malware such as the well-known remote access trojans (RATs) and more modern malware such as ransomware and cryptojacking. Existing security solutions implemented on virtual servers fail to detect these newly created malware (zero-day attacks). In fact, by the time the security solution is updated, the organization has likely already been attacked. In this study, we present a designated framework aimed at trusted and secured detection of newly created and unknown instances of malware on virtual machines in an organization's private cloud. We took volatile memory dumps from a virtual machine (VM) in a secured and trusted manner, and analyzed all of the data within the memory dumps using the MinHash method; MinHash is well suited for the accurate detection of malware in VMs based on efficient volatile memory dump comparisons. The proposed framework is evaluated in a comprehensive set of experiments of increasing difficulty in which we also measured the detection performance of different classifiers (both similarity and machine learning-based classifiers, using collections of real-world, professional, notorious malware and legitimate applications. The evaluation results show that our framework can detect the anomalous state of a virtual server, as well as known, new, and unknown malware, with very high TPRs (100% for ransomware and RATs) and very low FPRs (1.8% for ransomware and no FPR for RATs). We also show how the methodology's performance can be improved, in terms of required time and storage space, saving more than 86% of these resources. Finally, we demonstrate the generalization capabilities and practicality of our methodology by using transfer learning and learning from just one virtual server in order to detect unknown malware on a different virtual server.

캐살 블랙의 영화 󰡔코리아󰡕(Korea)에 나타난 해방 후 아일랜드 가족의 시적 재구성

The purpose of this paper is to analyze the poetic techniques in Cathal Black’s Korea, a film in which he reconstructs the trajectory of the postliberation Irish family in the 1950s. In focusing on poetic aspects of repetition, defamiliarization, and irony in relation to the filmic techniques of symbol, montage, and voiceover, I will demonstrate how Black’s poetic reconstruction of the era goes against the grain of the forward movement of the narrative. First, Black adopts the repetition of symbolic objects like eels and electricity to represent the state of an era in which hope and despair coexist. Second, Black’s montage technique produces a defamiliarization effect. Juxtaposing disparate images and sounds, Black delivers a sense of shock and confusion, a key to understanding the spirit of the age. Finally, the ironic voiceover that unsuceessfully drives the narrative of the film works as a device for the reconstruction of recent Irish history. The narrator who lacks the capacity to overview his circumstance holds ambivalent attitudes toward the past, neither indiscriminately critical nor blindly nostalgic. With the repetition of symbolic objects, the radical montage, and the ironic voiceover, Black shows the anomalous state of postliberation Ireland in the 1950s, in which the trauma and nostalgia of the old generation and the hope and apprehension of the young generation are commingled like an oxymoron.

The state of stress in the aftershock area of the March 11, 2011 Tohoku earthquake

This paper presents the results of the stress inversion in the Earth’s crust in the Japanese seismic focal zone after the Tohoku earthquake of March 11, 2011. The stress tensor parameters are determined using the method of cataclastic analysis (MCA) of discontinuous displacements. The reconstruction of the stress state is based on earthquake focal mechanism data for magnitude range (Mw) 3.0–6.0. The calculations are performed at six depths. The 2011 Tohoku earthquake brought significant stress changes in the upper layers of the lithosphere of the continental slope (0-30 km). These changes have led to the emerging of extensive areas of horizontal extension here. The areas with changed geodynamic regime were not reduced over the past few years. The magnitude 9.0 Tohoku earthquake was a catastrophic mega earthquake and in this case the presence of an anomalous state of stress may take a long time.

A semisupervised autoencoder-based approach for anomaly detection in high performance computing systems

High Performance Computing (HPC) systems are complex machines with heterogeneous components that can break or malfunction. Automated anomaly detection in these systems is a challenging and critical task, as HPC systems are expected to work 24/7. The majority of the current state-of-the-art methods dealing with this problem are Machine Learning techniques or statistical models that rely on a supervised approach, namely the detection mechanism is trained to recognize a fixed number of different states (i.e. normal and anomalous conditions).In this paper a novel semi-supervised approach for anomaly detection in supercomputers is proposed, based on a type of neural network called autoencoder. The approach learns the normal state of the supercomputer nodes and after the training phase can be used to discern anomalous conditions from normal behavior; in doing so it relies only on the availability of data characterizing only the normal state of the system. This is different from supervised methods that require data sets with many examples of anomalous states, which are in general very rare and/or hard to obtain.The approach was tested on a real-life High Performance Computing system equipped with a monitoring infrastructure capable to generate large amount of data describing the system state. The proposed approach definitely outperforms the best current techniques for semi-supervised anomaly detection, with an increase in accuracy detection of around 12%. Two different implementations are discussed: one where each supercomputer node has a specific model and one with a single, generalized model for all nodes, in order to explore the trade-off between accuracy and ease of deployment.

Adiabatic variation of the charge density wave phase diagram in the 123 cuprate (CaxLa1−x)(Ba1.75−xLa0.25+x)Cu3Oy

In order to explain the emergence of the anomalous pseudogap state and high-temperature superconductivity in the cuprates, intense research activity over three decades has focused on unravelling the connection between the various instabilities of the underdoped regime. In the high-temperature superconductor (Ca$_x$La$_{1-x}$)(Ba$_{1.75-x}$La$_{0.25+x}$)Cu$_3$O$_y$ (CLBLCO) isovalent chemical substitution produces smooth changes to the CuO$_2$ plane buckling and the Cu(II)-to-apical-oxygen distance, allowing us to study the interdependence of charge-density-wave (CDW) order, superconductivity and the pseudogap at constant hole doping in two adiabatically connected representations of the 123 cuprate structure. In this study, resonant soft x-ray scattering measurements reveal the first observation of incommensurate CDW correlations in CLBLCO and demonstrate a lack of correlation between $T_{\text{CDW}}$ and the pseudogap crossover temperature ($T^{\ast}$). This result disfavours a scenario in which the opening of the pseudogap at $T^{\ast}$ results from fluctuating CDW correlations.

Sequential Anomaly Detection Under a Nonlinear System Cost

We consider the problem of anomaly detection among $K$ heterogeneous processes. At each given time, one process is probed, and the random observations follow two different distributions, depending on whether the process is normal or abnormal. Each anomalous process incurs a cost until its anomaly is identified and fixed, and the cost is a nonlinear (specifically, polynomial with degree $d$ ) function of the duration of the anomalous state. The objective is a sequential search strategy that minimizes the total expected cost incurred by all the processes during the detection process under reliability constraints. We propose a search algorithm that consists of exploration, exploitation, and sequential testing phases. We establish its asymptotic optimality and analyze the approximation ratio and the regret under computational constraints.

Magneto-Oscillations and Anomalous Current States in a Photoexcited Electron Gas on Liquid Helium

The paper reviews a novel class of phenomena observed recently in the two-dimensional (2D) electron system formed on the free surface of liquid helium in the presence of a magnetic field directed normally and exposed to microwave radiation. The distinctive feature of these nonequilibrium phenomena is magnetoconductivity oscillations induced by inter-subband (out-of-plane) and intra-subband (in-plane) microwave excitations. The conductivity magneto-oscillations induced by intra-subband excitation are similar to remarkable microwave-induced resistance oscillations (MIRO) reported for semiconductor heterostructures. Investigations of microwave-induced conductivity oscillations on liquid helium helped with understanding of the origin of MIRO. Much stronger microwave-induced conductivity oscillations were observed and well described theoretically for resonant inter-subband microwave excitation. At strong powers, such excitation leads to zero-resistance states, the in-plane redistribution of electrons, self-generated audio-frequency oscillations, and incompressible states. These phenomena are caused by unusual current states of the 2D electron system formed under resonant microwave excitation.

An Addendum to the elliptic torsion anomalous conjecture in codimension 2

The torsion anomalous conjecture states that for any variety V in an abelian variety there are only finitely many maximal V -torsion anomalous varieties. We prove this conjecture for V of codimension 2 in a product E^N of an elliptic curve E without CM, complementing previous results for E with CM. We also give an effective upper bound for the normalized height of these maximal V -torsion anomalous varieties.

Anomalous transparency induced by cooperative disorders in phonon transport

Wave transport through disordered materials is of broad interest in science and engineering. It has been generally believed that long-range transport cannot exist in low-dimensional disordered systems due to the Anderson localization of all states. However, in this work we report the anomalous transparency of phonon transport induced by cooperative effects of mass and force-constant disorders in completely random harmonic wires. In contrast to the full localization in mass-disordered wire, an anomalous transparent phonon state can emerge due to the intrinsic cooperation of disordered mass and force constants. We obtain the frequency of the transparent state, tuned by the disordered force constants and masses. Consequently, the phonon transport in the completely disordered system falls into three different regimes: the full localization, resonant, and sub-ballistic regimes. While there exists a single nonzero transparent frequency in the resonant regime, transparent states in a wide range of frequencies can be present in the sub-ballistic regime, which significantly enhances the thermal conductivity of disordered wires. These findings may open new doors to modulate thermal transport and design thermal devices, including thermal filter and high-thermal-conductivity materials.

Modulation of tropical cyclones in the southeastern part of western North Pacific by tropical Pacific decadal variability

The tropical cyclone (TC) genesis number in the western North Pacific (WNP) exhibits a pronounced decadal decrease around the mid-1990s, with prominent seasonal and spatial inhomogeneity. This decadal shift of TC activity is mostly confined to the southeastern part of the WNP and occurs mainly during the second half of the calendar year. Accordingly, westward and northeastward TC recurving movements strongly decreased in recent decades after 1995 compared with TC tracks in the earlier period (1979–1994). We find that this TC activity decadal change is associated with tropical Pacific decadal variability, which is measured here by a low-pass filtered Nino3.4 index. In contrast to the earlier period, the anomalous cold mean state in the tropical Pacific during recent decades favored the enhancement of zonal vertical wind shear (UVWS) and suppressed TC activity. This tropical Pacific mean state change is possibly related to decadal changes of El Nino–Southern Oscillation (ENSO) properties (i.e., more La Nina events occurred during recent decades). This relationship between tropical Pacific mean state change and the UVWS in the southeastern WNP on decadal timescales is further validated based on longer observations (1951–2017) and control simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5). The statistical relationships between TC activity and the Pacific Decadal Oscillation (PDO) or Atlantic Multidecadal Oscillation (AMO) are weaker and insignificant, both for the observations and for simulations. Our results imply that decadal variations of the tropical Pacific mean state should be taken into account when predicting WNP TC activities on decadal timescales.

Magnetotransport Properties of the Orbital-Ordered State of Ba1−xSrxV13O18

Magnetotransport properties were investigated for single crystals of Ba1−xSrxV13O18 (\(x = 0,0.05,0.2,1\)), which exhibit an anomalous orbital-ordered state with electrical conduction at low temper...