20 research outputs found
Non-Hermitian skin clusters from strong interactions
Strong, non-perturbative interactions often lead to new exciting physics, as
epitomized by emergent anyons from the Fractional Quantum Hall effect. Within
the actively investigated domain of non-Hermitian physics, we discover a new
family of states known as non-Hermitian skin clusters. Taking distinct forms as
Vertex, Topological, Interface, Extended, and Localized skin clusters, they
generically originate from asymmetric correlated hoppings on a lattice, in the
strongly interacting limit with quenched single-body energetics. Distinct from
non-Hermitian skin modes which accumulate at boundaries, our skin clusters are
predominantly translation-invariant particle clusters. As purely interacting
phenomena, they fall outside the purview of generalized Brillouin zone
analysis, although our effective lattice formulation provides alternative
analytic and topological characterization. Non-Hermitian skin clusters
fundamentally originate from the fragmentation structure of the Hilbert space
and may thus be of significant interest in modern many-body contexts like the
ETH and quantum scars.Comment: 21 pages,18 figures, and 1 table in total. Comments are welcom
Kinked linear response from non-Hermitian pumping
Non-Hermiticity is known to give rise to modified topological bulk-boundary
correspondences, which predict the presence of topological boundary modes
through appropriately modified topological invariants. Yet, little is currently
known about how non-Hermiticity affects the precise linear response of
wavepackets beyond their overall spectral flow. In this work, we discover that
generically, non-Hermiticity gives rise to abrupt and prominent kinks in the
semi-classical wavepacket trajectories of quantum gases, despite the absence of
sudden physical impulses. This physically stems from a hitherto
under-appreciated intrinsic non-locality from non-Hermitian pumping, even if
all physical couplings are local, thereby resulting in enigmatic singularities
in the band structure that lead to discontinuous band geometry and Berry
curvature. For concrete experimental demonstration, we propose an ultracold
atomic setup in a two-dimensional optical lattice with laser-induced loss, such
that response kinks can be observed without fine-tuning in the physical atomic
cloud dynamics. Our results showcases unique non-monotonic behavior from
non-Hermitian pumping beyond the non-Hermitian skin effect, and suggests new
avenues for investigating non-Hermitian dynamics in ultracold atomic platforms.Comment: 21 pages, 7 figure
Universal competitive spectral scaling from the critical non-Hermitian skin effect
Recently, it was discovered that certain non-Hermitian systems can exhibit
qualitative different properties at different system sizes, such as being
gapless at small sizes and having topological edge modes at large sizes .
This dramatic system size sensitivity is known as the critical non-Hermitian
skin effect (cNHSE), and occurs due to the competition between two or more
non-Hermitian pumping channels. In this work, we rigorously develop the notion
of a size-dependent generalized Brillouin zone (GBZ) in a general
multi-component cNHSE model ansatz, and found that the GBZ exhibits a universal
scaling behavior. In particular, we provided analytical
estimates of the scaling rate in terms of model parameters, and
demonstrated their good empirical fit with two paradigmatic models, the coupled
Hatano-Nelson model with offset, and the topologically coupled chain model with
offset. We also provided analytic result for the critical size , below
which cNHSE scaling is frozen. The cNHSE represents the result of juxtaposing
different channels for bulk-boundary correspondence breaking, and can be
readily demonstrated in non-Hermitian metamaterials and circuit arrays.Comment: 26 pages, 12 figure
Proposal for observing Yang-Lee criticality in Rydberg atomic arrays
Yang-Lee edge singularities (YLES) are the edges of the partition function
zeros of an interacting spin model in the space of complex control parameters.
They play an important role in understanding non-Hermitian phase transitions in
many-body physics, as well as characterizing the corresponding non-unitary
criticality.Even though such partition function zeroes have been measured in
dynamical experiments where time acts as the imaginary control field,
experimentally demonstrating such YLES criticality with a physical imaginary
field has remained elusive due to the difficulty of physically realizing
non-Hermitian many-body models. We provide a protocol for observing the YLES by
detecting kinked dynamical magnetization responses due to broken PT symmetry,
thus enabling the physical probing of non-unitary phase transitions in
non-equilibrium settings. In particular, scaling analyses based on our
non-unitary time evolution circuit with matrix product states (tMPS) accurately
recover the exponents uniquely associated with the corresponding non-unitary
CFT. We provide an explicit proposal for observing YLES criticality in Floquet
quenched Rydberg atomic arrays with laser-induced loss, which paves the way
towards an universal platform for simulating non-Hermitian many-body dynamical
phenomena.Comment: 19 pages, 11 figure
State-of-the-art methods for exposure-health studies: Results from the exposome data challenge event
The exposome recognizes that individuals are exposed simultaneously to a multitude of different environmental factors and takes a holistic approach to the discovery of etiological factors for disease. However, challenges arise when trying to quantify the health effects of complex exposure mixtures. Analytical challenges include dealing with high dimensionality, studying the combined effects of these exposures and their interactions, integrating causal pathways, and integrating high-throughput omics layers. To tackle these challenges, the Barcelona Institute for Global Health (ISGlobal) held a data challenge event open to researchers from all over the world and from all expertises. Analysts had a chance to compete and apply state-of-the-art methods on a common partially simulated exposome dataset (based on real case data from the HELIX project) with multiple correlated exposure variables (P > 100 exposure variables) arising from general and personal environments at different time points, biological molecular data (multi-omics: DNA methylation, gene expression, proteins, metabolomics) and multiple clinical phenotypes in 1301 mother–child pairs. Most of the methods presented included feature selection or feature reduction to deal with the high dimensionality of the exposome dataset. Several approaches explicitly searched for combined effects of exposures and/or their interactions using linear index models or response surface methods, including Bayesian methods. Other methods dealt with the multi-omics dataset in mediation analyses using multiple-step approaches. Here we discuss features of the statistical models used and provide the data and codes used, so that analysts have examples of implementation and can learn how to use these methods. Overall, the exposome data challenge presented a unique opportunity for researchers from different disciplines to create and share state-of-the-art analytical methods, setting a new standard for open science in the exposome and environmental health field
Spatial heterogeneity and infection patterns on epidemic transmission disclosed by a combined contact-dependent dynamics and compartmental model.
Epidemics, such as COVID-19, have caused significant harm to human society worldwide. A better understanding of epidemic transmission dynamics can contribute to more efficient prevention and control measures. Compartmental models, which assume homogeneous mixing of the population, have been widely used in the study of epidemic transmission dynamics, while agent-based models rely on a network definition for individuals. In this study, we developed a real-scale contact-dependent dynamic (CDD) model and combined it with the traditional susceptible-exposed-infectious-recovered (SEIR) compartment model. By considering individual random movement and disease spread, our simulations using the CDD-SEIR model reveal that the distribution of agent types in the community exhibits spatial heterogeneity. The estimated basic reproduction number R0 depends on group mobility, increasing logarithmically in strongly heterogeneous cases and saturating in weakly heterogeneous conditions. Notably, R0 is approximately independent of virus virulence when group mobility is low. We also show that transmission through small amounts of long-term contact is possible due to short-term contact patterns. The dependence of R0 on environment and individual movement patterns implies that reduced contact time and vaccination policies can significantly reduce the virus transmission capacity in situations where the virus is highly transmissible (i.e., R0 is relatively large). This work provides new insights into how individual movement patterns affect virus spreading and how to protect people more efficiently
Magnetically Guided Capsule Endoscopy in Pediatric Patients with Abdominal Pain
Background and Aims. Magnetically guided capsule endoscopy (MGCE) offers a noninvasive method of evaluating both the gastric cavity and small intestine; however, few studies have evaluated MGCE in pediatric patients. We investigated the diagnostic efficacy of MGCE in pediatric patients with abdominal pain. Patients and Methods. We enrolled 48 patients with abdominal pain aged 6–18 years. All patients underwent MGCE to evaluate the gastric cavity and small intestine. Results. The cleanliness of the gastric cardia, fundus, body, angle, antrum, and pylorus was assessed satisfactorily in 100%, 85.4%, 89.6%, 100%, 97.9%, and 100% of patients, respectively. The subjective percentage visualization of the gastric cardia, fundus, body, angle, antrum, and pylorus was 84.8%, 83.8%, 88.5%, 87.7%, 95.2%, and 99.6%, respectively. Eighteen (37.5%) patients had 19 gastrointestinal tract lesions: one esophageal, three in the gastric cavity, and 15 in the small intestine. No adverse events occurred during follow-up. Conclusions. MGCE is safe, convenient, and tolerable for evaluating the gastric cavity and small intestine in pediatric patients. MGCE can effectively diagnose pediatric patients with abdominal pain
gStore: A Graph-based SPARQL Query Engine
We address efficient processing of SPARQL queries over RDF datasets. The proposed techniques, incorporated into the gStore system, handle, in a uniform and scalable manner, SPARQL queries with wildcards and aggregate operators over dynamic RDF datasets. Our approach is graph-based. We store RDF data as a large graph, and also represent a SPARQL query as a query graph. Thus the query answering problem is converted into a subgraph matching problem. To achieve efficient and scalable query processing, we develop an index, together with effective pruning rules and efficient search algorithms. We propose techniques that use this infrastructure to answer aggregation queries. We also propose an effective maintenance algorithm to handle online updates over RDF repositories. Extensive experiments confirm the efficiency and effectiveness of our solutions
Magnetic-Guided Capsule Endoscopy in the Diagnosis of Gastrointestinal Diseases in Minors
Objective. This study aimed at investigating the clinical value of magnetic-guided capsule endoscopy (MGCE) in the diagnosis of gastrointestinal diseases in minors. Methods. Eighty-four minor patients hospitalized in the pediatric department at Ruijin Hospital between June 2015 and January 2018 were enrolled for this study. Following bowel preparation, all patients underwent MGCE. The feasibility, safety, diagnostic yield, and sensitivity of MGCE were analyzed. Patients were followed up for more than 2 weeks. Results. The main indications for MGCE in minors were Crohn’s disease, gastrointestinal bleeding, and abdominal pain. The main causes of gastric disease were gastric inflammatory hyperplasia, exudative gastritis, and polyps. The most common small bowel diseases in minors were Crohn’s disease, Henoch-Schonlein purpura, and polyps. The diagnostic yield in the stomach and small intestine was 13.1% and 28.6%, respectively, and the sensitivity was 100% and 96.0%, respectively. No adverse events occurred. Conclusion. MGCE is a safe, effective, and well-tolerated procedure with good sensitivity and has a potential clinic value for the diagnosis of gastrointestinal diseases in minors