Time Evolution Research Articles

Achalasia: diagnostic delay and manometric characteristics with high-resolution solid-state and perfusion equipment.

The early diagnosis of achalasia requires a high degree of clinical suspicion, and delays in diagnosis are frequent. High-resolution oesophageal manometry (HRM) is the gold standard for its diagnostic confirmation. There are two HRM systems, perfusion and solid-state, which allow its classification into three subtypes: I, or classical; II, or with pan-oesophageal pressurization; and III, or spastic. To determine the clinical and manometric characteristics of the three subtypes with high-resolution perfusion and solid-state equipment and the time of evolution until diagnosis. This was a multicentre, observational, retrospective study of patients from the INTEGRA database of the Spanish Association of Neurogastroenterology and Motility who were diagnosed with primary achalasia confirmed by HRM, who fell under the Chicago Classification v3.0, and who had not been treated. The study included 110 patients (subtype I, N = 14; subtype II, N = 73; subtype III, N = 23). The HRM equipment was perfusion for 49 and solid-state for 61. The mean age was 61.8 ± 14 years (age range 44-81), the age was lower in subtype II, and the sex distribution was similar. The time of clinical evolution until diagnosis was > 12 months (51.6%), subtype II being the one that was diagnosed earlier and the most often (66.3%). Dysphagia was the most frequent symptom (90.5%). According to the comparative analysis by high-resolution perfusion and solid-state oesophageal manometry equipment, the baseline pressure of the lower oesophageal sphincter was higher in the solid-state oesophagus, but the difference was not statistically significant. The median integrated relaxation pressure at 4 seconds (IRP4) was similar (21 mmHg) between the perfusion and solid-state measurements. We describe the ranges of IRP4 in achalasia patients with both systems and confirm the possibility of achalasia even when IRP4 is within the normal range. Achalasia in our environment has a significant diagnostic delay. No significant differences were observed in the oesophagogastric junction between the two groups diagnosed with perfusion and solid-state equipment.

Extraction of nonlinearity in neural networks with Koopman operator

Nonlinearity plays a crucial role in deep neural networks. In this paper, we investigate the degree to which the nonlinearity of the neural network is essential. For this purpose, we employ the Koopman operator, extended dynamic mode decomposition, and the tensor-train format. The Koopman operator approach has been recently developed in physics and nonlinear sciences; the Koopman operator deals with the time evolution in the observable space instead of the state space. Since we can replace the nonlinearity in the state space with the linearity in the observable space, it is a hopeful candidate for understanding complex behavior in nonlinear systems. Here, we analyze learned neural networks for the classification problems. As a result, the replacement of the nonlinear middle layers with the Koopman matrix yields enough accuracy in numerical experiments. In addition, we confirm that the pruning of the Koopman matrix gives sufficient accuracy even at high compression ratios. These results indicate the possibility of extracting some features in the neural networks with the Koopman operator approach.

Station-keeping HAPS mission through optimal sprint and drift trajectories

Due to the latest technological breakthroughs, High-Altitude Pseudo Satellites (HAPS) have recently become a feasible solution with great potential in the aerospace industry for Earth observation and communications, among other applications. Minimizing the energy consumption of these solar powered platforms is critical and, in the case of lighter than air vehicles, leads to smaller and more manageable platforms. When stratospheric airships perform a station-keeping mission, a certain displacement from the Earth surface reference point is usually admissible. This flexibility makes it possible to define an optimal control law for the airship that minimizes the energy required to fly in a 24-hour cycle, leading to a sprint and drift trajectory. This study analyzes the impact on the energy balance of the mission that stems from the changes in the allowed station-keeping radius. It also considers the effects of the daylight hours, the wind intensity, and the characteristics of the onboard energy system. The associated optimal control problems are rigorously solved numerically by means of a transcription method with regularization. The results define the optimal sprint and drift trajectories adapted to every scenario, providing the time evolution of the available power that controls the flight. The analysis indicates that following the optimal trajectory leads to weight savings in the energy system of about 5.4 kilograms per kilometer of the station-keeping radius. It entails that, for example, if a 20 kilometer radius is allowed, the energy required decreases more than 6% and the payload capacity increases about a 43% when compared to the fixed-point flight.

Adaptive Trotterization for Time-Dependent Hamiltonian Quantum Dynamics Using Piecewise Conservation Laws.

Digital quantum simulation relies on Trotterization to discretize time evolution into elementary quantum gates. On current quantum processors with notable gate imperfections, there is a critical trade-off between improved accuracy for finer time steps, and increased error rate on account of the larger circuit depth. We present an adaptive Trotterization algorithm to cope with time dependent Hamiltonians, where we propose a concept of piecewise "conserved" quantities to estimate errors in the time evolution between two (nearby) points in time; these allow us to bound the errors accumulated over the full simulation period. They reduce to standard conservation laws in the case of time independent Hamiltonians, for which we first developed an adaptive Trotterization scheme [H. Zhao et al., Making Trotterization adaptive and energy-self-correcting for NISQ devices and beyond, PRX Quantum 4, 030319 (2023).2691-339910.1103/PRXQuantum.4.030319]. We validate the algorithm for a time dependent quantum spin chain, demonstrating that it can outperform the conventional Trotter algorithm with a fixed step size at a controlled error.

The dynamical distribution of continuous service time model involving the non-Maxwellian collision kernel and value functions

Abstract The distribution of continuous service time in call centers is investigated. A non-Maxwellian collision kernel combining two different value functions in the interaction rule are used to describe the evolution of continuous service time, respectively. Using the statistical mechanical and asymptotic limit methods, Fokker-Planck equations are derived from the corresponding Boltzmann-type equations with non-Maxwellian collision kernels. The steady-state solutions of the Fokker-Planck equation are obtained in exact form. Numerical experiments are provided to support our results under different parameters.

Unravelling quantum dynamics using flow equations

AbstractThe study of many-body quantum dynamics in strongly correlated systems is extremely challenging. To date, few numerical methods exist that are capable of simulating the non-equilibrium dynamics of two-dimensional quantum systems, which is partly due to complexity theoretic obstructions. In this work, we present a technique able to overcome this obstacle, by combining continuous unitary flow techniques with the newly developed method of scrambling transforms. We overcome the assumption that approximately diagonalizing the Hamiltonian cannot lead to reliable predictions for relatively long times. Rather, we show that the method achieves good accuracy in both localized and delocalized phases and makes reliable predictions for a number of quantities including infinite-temperature autocorrelation functions. We complement our findings with rigorous incremental bounds on the truncation error. Our approach shows that, in practice, the exploration of intermediate-scale time evolution may be more feasible than is commonly assumed, challenging near-term quantum simulators.

Design of shortcuts to adiabaticity for Bose-Einstein condensates dynamics in soliton Josephson junctions

Abstract This article primarily establishes a two-soliton system and employs the Lewis-Riesenfeld invariant inverse control method to achieve shortcuts to adiabaticity (STA) technology. We study on the atomic soliton Josephson junctions (SJJs) device and subsequently compare and analyze it with atomic bosonic Josephson junctions (BJJs). Moreover, we use higher-order expressions of the auxiliary equations to optimize the results and weaken the detrimental effect of the sloshing amplitude. We find that in the adiabatic shortcut evolution of two systems with time-containing tunnelling rates, the SJJs system is more robust over a rather short time evolution. In comparison with linear ramping, the STA technique is easier to achieve with the precise modulation of the quantum state in the SJJs system.

Wigner Analysis of Particle Dynamics and Decoherence in Wide Nonharmonic Potentials

We derive an analytical expression of a Wigner function that approximately describes the time evolution of the one-dimensional motion of a particle in a nonharmonic potential. Our method involves two exact frame transformations, accounting for both the classical dynamics of the centroid of the initial state and the rotation and squeezing about that trajectory. Subsequently, we employ two crucial approximations, namely the constant-angle and linearized-decoherence approximations, upon which our results rely. These approximations are effective in the regime of wide potentials and small fluctuations, namely potentials that enable spatial expansions orders of magnitude larger than the one of the initial state but that remain smaller compared to the relevant dynamical length scale (e.g., the distance between turning points). Our analytical result elucidates the interplay between classical and quantum physics and the impact of decoherence during nonlinear dynamics. This analytical result is instrumental to designing, optimizing, and understanding proposals using nonlinear dynamics to generate macroscopic quantum states of massive particles.

Canonical Typicality for Other Ensembles than Micro-canonical

AbstractWe generalize Lévy’s lemma, a concentration-of-measure result for the uniform probability distribution on high-dimensional spheres, to a much more general class of measures, so-called GAP measures. For any given density matrix $$\rho $$ ρ on a separable Hilbert space $${\mathcal {H}}$$ H , $${\textrm{GAP}}(\rho )$$ GAP ( ρ ) is the most spread-out probability measure on the unit sphere of $${\mathcal {H}}$$ H that has density matrix $$\rho $$ ρ and thus forms the natural generalization of the uniform distribution. We prove concentration-of-measure whenever the largest eigenvalue $$\Vert \rho \Vert $$ ‖ ρ ‖ of $$\rho $$ ρ is small. We use this fact to generalize and improve well-known and important typicality results of quantum statistical mechanics to GAP measures, namely canonical typicality and dynamical typicality. Canonical typicality is the statement that for “most” pure states $$\psi $$ ψ of a given ensemble, the reduced density matrix of a sufficiently small subsystem is very close to a $$\psi $$ ψ -independent matrix. Dynamical typicality is the statement that for any observable and any unitary time evolution, for “most” pure states $$\psi $$ ψ from a given ensemble the (coarse-grained) Born distribution of that observable in the time-evolved state $$\psi _t$$ ψ t is very close to a $$\psi $$ ψ -independent distribution. So far, canonical typicality and dynamical typicality were known for the uniform distribution on finite-dimensional spheres, corresponding to the micro-canonical ensemble, and for rather special mean-value ensembles. Our result shows that these typicality results hold also for $${\textrm{GAP}}(\rho )$$ GAP ( ρ ) , provided the density matrix $$\rho $$ ρ has small eigenvalues. Since certain GAP measures are quantum analogs of the canonical ensemble of classical mechanics, our results can also be regarded as a version of equivalence of ensembles.

From dinosaurs to birds: paleomacroecological analysis of the body size inversion in the maniraptor lineage

Large taxonomic groups, distributed over vast geological periods, may exhibit wide patterns of morphological variation, such as variation in body size and complexity of living beings. Some studies seek to determine whether these trends of increasing or decreasing size and complexity result from persistent directional forces (e.g., natural selection) or from non-directional (random) trends produced by constraint limits. These mechanisms have been characterized as "active or directed" and "passive" trend processes, respectively. Understanding these variation patterns allows assessing hypotheses within a paleomacroecological context, such as Cope's Rule, which suggests that lineages with longer evolutionary time spans tend to increase in size. This pattern has been demonstrated in various groups of fossil vertebrates, such as dinosaurs. However, the Maniraptora lineage (ancestral to groups that gave rise to birds) seems to exhibit an inverted pattern, with a reduction in body size in recent lineages. Tests indicate that this asymmetry in size evolution can be explained by passive or active trends, i.e., random size variation or directional selection. In this case, an "Inverted Cope's Rule" could indicate directional selection for size reduction in the Maniraptora lineage towards the derivation of birds. Body size and time distribution vectors will be derived for each lineage, evaluating the general trend of size variation. If asymmetry in size evolution is observed, a Subclade Test will be conducted to assess if a specific subclade repeats the asymmetric distribution pattern. The goal of this project is to assess active and/or passive trends related to body size variation in Maniraptora dinosaurs, using fossil data from the Paleobiology Database and the Natural History Museum Database.

Diagnosing Thermalization Dynamics of Non-Hermitian Quantum Systems via GKSL Master Equations

Abstract The application of the eigenstate thermalization hypothesis to non-Hermitian quantum systems has become one of the most important topics in dissipative quantum chaos, recently giving rise to intense debates. The process of thermalization is intricate, involving many time-evolution trajectories in the reduced Hilbert space of the system. By considering two different expansion forms of the density matrices adopted in the biorthogonal and right-state time evolutions, we derive two versions of the Gorini–Kossakowski–Sudarshan–Lindblad (GKSL) master equations describing the non-Hermitian systems coupled to a bosonic heat bath in thermal equilibrium. By solving the equations, we identify a sufficient condition for thermalization under both time evolutions, resulting in Boltzmann biorthogonal and right-eigenstate statistics, respectively. This finding implies that the recently proposed biorthogonal random matrix theory needs an appropriate revision. Moreover, we exemplify the precise dynamics of thermalization and thermodynamic properties with test models.

Projected data assimilation using sliding window proper orthogonal decomposition

Prediction of the state evolution of complex high-dimensional nonlinear systems is challenging due to the nonlinear sensitivity of the evolution to small inaccuracies in the model. Data Assimilation (DA) techniques improve state estimates by combining model simulations with real-time data. Few DA techniques can simultaneously handle nonlinear evolution, non-Gaussian uncertainty, and the high dimension of the state. We recently proposed addressing these challenges using a POD technique that projects the physical and data models into a reduced-dimensional subspace. Proper Orthogonal Decomposition (POD) is a tool to extract spatiotemporal patterns (modes) that dominate the observed data. We combined the POD-based projection operator, computed in an offline fashion, with a DA scheme that models non-Gaussian uncertainty in lower dimensional subspace. If the model parameters change significantly during time evolution, the offline computation of the projection operators ceases to be useful. We address this challenge using a Sliding Window POD (SW-POD), which recomputes the projection operator based on a sliding subset of snapshots from the entire evolution. The physical model projection is updated dynamically in terms of modes and number of modes, and the data model projection is also chosen to promote a sparse approximation. We test the efficacy of this technique on a modified Lorenz'96 model (L96) with a time-varying forcing and compare it with the time-invariant offline projected algorithm. In particular, dynamically determined physical and data model projections decrease the Root Mean Squared Error (RMSE) and the resampling rate.

Quasinormal modes and greybody factor of a Lorentz-violating black hole

Recently, a static spherically symmetric black hole solution was found in gravity nonminimally coupled a background Kalb-Ramond field. The Lorentz symmetry is spontaneously broken when the Kalb-Ramond field has a nonvanishing vacuum expectation value. In this work, we focus on the quasinormal modes and greybody factor of this black hole. The master equations for the perturbed scalar field, electromagnetic field, and gravitational field can be written into a Schrödinger equation. We use three methods to solve the quasinormal frequencies in the frequency domain. The results agree well with each other. The time evolution of a Gaussian wave packet is studied. The quasinormal frequencies fitted from the time evolution data agree well with that of frequency domain. The greybody factor is calculated by Wentzel-Kramers-Brillouin (WKB) method. The effect of the Lorentz-violating parameter on the quasinormal modes and greybody factor are also studied.

Fast entangling quantum gates with almost-resonant modulated driving

Recently, the method of using a special category of synthetic analytical pulses under off-resonant conditions has improved the experimental performance of two- and multi-qubit gates in the cold atom qubit platform. In order to explore more possibilities and wider ranges of options, we design and analyze the method of almost-resonant modulated driving (ARMD) in constructing fast-speed and high-fidelity quantum logic gates. Whilst the modulation forms the key concept of high-fidelity Rydberg blockade gates so far, the on-off resonance condition can lead to nontrivial nuances in the styles of dynamics, and the ARMD gate protocols have its different characteristic mechanisms in quantum physics compared with the off-resonant gate processes. In particular, ARMD gates usually have abrupt phase changes and at certain points during the time evolution. From a more fundamental point of view, both the resonant and off-resonant methods all together belong to the unitary operation family of fast modulated driving with respect to precisely characterized inter-qubit interactions, which usually allows the quantum logic gate to conclude within one continuous pulse. We anticipate the ARMD gates to work well with the Rydberg dipole-dipole interaction and will serve as a helpful tool in the future studies of the cold atom qubit platform.

Diverse Antiphage Defenses Are Widespread Among Prophages and Mobile Genetic Elements.

Bacterial viruses known as phages rely on their hosts for replication and thus have developed an intimate partnership over evolutionary time. The survival of temperate phages, which can establish a chronic infection in which their genomes are maintained in a quiescent state known as a prophage, is tightly coupled with the survival of their bacterial hosts. As a result, prophages encode a diverse antiphage defense arsenal to protect themselves and the bacterial host in which they reside from further phage infection. Similarly, the survival and success of prophage-related elements such as phage-inducible chromosomal islands are directly tied to the survival and success of their bacterial host, and they also have been shown to encode numerous antiphage defenses. Here, we describe the current knowledge of antiphage defenses encoded by prophages and prophage-related mobile genetic elements.

Wound-dependent leg amputations to combat infections in an ant society

Open wounds pose major infection and mortality risks in animals.1,2 To reduce these risks, many animal species apply antimicrobial compounds on their wounds.1,2,3,4 Ant societies use antimicrobial secretions from the metapleural gland to combat pathogens,5,6,7,8,9,10 but this gland has been lost over evolutionary time in several genera, including Camponotus.11 To understand how infected wounds are handled without the use of antimicrobial secretions from the metapleural gland, we conducted behavioral and microbiological experiments in Camponotus floridanus. When we experimentally injured a worker's leg at the femur, nestmates amputated the injured limb by biting the base (trochanter) of the leg until it was severed, thereby significantly increasing survival compared to ants that did not receive amputations. However, when the experimental injury was more distal (at the tibia), nestmates did not amputate the leg and instead directed more wound care to the injury site. Experimental amputations also failed to improve survival in ants with infected tibia injuries unless the leg was amputated immediately after pathogen exposure. Micro-CT scans revealed that the muscles likely responsible for leg hemolymph circulation are predominantly in the femur. Thus, it is likely that femur injuries, by attenuating hemolymph flow, provide sufficient time for workers to perform amputations before pathogen spread. Overall, this study provides the first example of the use of amputations to treat infected individuals in a non-human animal and demonstrates that ants can adapt their type of treatment depending on the location of wounds.

MHD-FiT: MHD-based dynamic reconstruction of tokamak plasma configuration

This paper introduces an innovative method for reconstructing 2D magnetic flux contours and plasma parameters of dynamically moving tokamak plasmas. While conventional methods like EFIT, based on the Grad–Shafranov equation, are suitable for plasma equilibria with a single magnetic axis, our approach utilizes the MHD equations and shows promise for tokamak plasmas in motion or containing multiple magnetic axes, which may not strictly adhere to plasma equilibria. By utilizing limited edge magnetic probe measurements, our developed model successfully reconstructs the time evolution of two merging plasma toroids in the TS-6 experiment. A comparison with direct 2D magnetic probe measurements in a low β regime reveals a reconstruction error of approximately 3%.

Unbalanced core detector (UCD): a novel direct-reading dosimeter for FLASH radiotherapy

FLASH radiotherapy (FRT) is a novel radiotherapy technique based on dose rates that are several orders of magnitude greater than those used in conventional radiotherapy (40 Gy/s vs. 0.5–5 Gy/min). FRT is still in its preclinical and early clinical stage of development. However these studies indicate that FRT is more effective in sparing normal tissues from radiation-related side effects, as compared to conventional radiotherapy. This is the so-called "FLASH effect" and was observed with multi-MeV electron beams. Before FRT is made available to humans, more basic research is needed to fully understand its radiobiology fundamentals. Meanwhile, suitable radiation sources and dosimetric tools are gradually becoming available. Within this framework, INFN-LNF developed the Unbalanced Core Detector (UCD), a novel type of electron dosimeter designed to operate in the FRT domain. UCD main characteristics are the nearly isotropic response, the independence from the electron energy, the very high radiation resistance, the linearity up to dose rates of MGy/s and the possibility to record the time evolution of a single radiation pulse. UCD was tested using 7 and 9 MeV electron beams produced with the ElectronFlash accelerator from Sordina IORT Technologies (SIT S.p.A.) in Aprilia, Italy. UCD was used to measure dose distributions in a water phantom. The results well compare to those obtained with a flashDiamond detector from PTW.

Periodic response and stability analysis of a bistable viscoelastic von Mises truss

This paper examines the effect of viscoelasticity on the periodic response of a lumped parameter viscoelastic von Mises truss. The viscoelastic system is described by a second-order equation that governs the mechanical motion coupled to a first-order equation that governs the time evolution of the viscoelastic forces. The viscoelastic force evolves at a much slower rate than the elastic oscillations in the system. This adds additional time scales and degrees of freedom to the system compared to its viscous counterparts. The focus of this study is on the system’s behavior under harmonic loading, which is expected to show both regular and chaotic dynamics for certain combinations of forcing frequency and amplitude. While the presence of chaos in this system has already been demonstrated, we shall concentrate only on the periodic solutions. The presence of the intrawell and interwell periodic oscillations is revealed using the Harmonic Balance method. The study also looks at the influence of parameter changes on the system’s behavior through bifurcation diagrams, which enable us to identify optimal system parameters for maximum energy dissipation. Lastly, we formulate an equivalent viscous system using an energy-based approach. We observe that a naive viscous model fails to capture the behavior accurately depending on the system and excitation parameters, as well as the type of excitation. This underscores the necessity to study the full-scale viscoelastic system.

Influence of Time-Varying Freestream Conditions on the Dynamics of Unsteady Boundary-Layer Separation

Unsteady flow separation of a turbulent boundary layer under dynamic pressure gradients is investigated using the Large-Eddy Simulation technique. The unsteadiness is introduced by prescribing an oscillating freestream vertical-velocity profile at the top boundary of the domain. Although previous studies, including Ambrogi et al. (Journal of Fluid Mechanics, Vol. 945, Aug. 2022, p. A10) and Ambrogi et al. (Journal of Fluid Mechanics, Vol. 972, Oct. 2023, p. A36), focused on the kinematics of the flow and the effects of the oscillation frequency on flow separation, the goal of this paper is to analyze the effects of three time-varying freestream-forcing profiles while the oscillation frequency is kept the same for all Cases. Whereas in Case A the freestream-velocity profile changes from suction–blowing to blowing–suction in a complete cycle, Cases B and C are both suction–blowing only and the strength of the adverse pressure gradient is modulated in time. Moreover, the boundary layer in Case B never approaches a zero-pressure gradient condition. A closed separation bubble is formed for all Cases; however, its dimensions change depending on the far-field forcing. The time evolution of turbulent kinetic energy (TKE) reveals an advection mechanism of turbulent structures out of the domain for all Cases. Whereas in Case A and C the high-TKE region, generated in the separated shear layer, is washed out of the domain as a rigid body, in Case B the separation bubble remains present and the advection mechanism of TKE is characterized by a breathing pattern.