bluuebunny/crossref_metadata_2025_split huggingface dataset:
An inverse random source problem for the one-dimensional Helmholtz equation with attenuation
Authors: Li Peijun , Wang Xu 
Published: November 2020

Abstract
This paper is concerned with an inverse random source problem for the one-dimensional stochastic Helmholtz equation with attenuation. The source is assumed to be a microlocally isotropic Gaussian random field with its covariance operator being a classical pseudo-differential operator. The random sources under consideration are equivalent to the generalized fractional Gaussian random fields which include rough fields and can be even rougher than the white noise, and hence should be interpreted as distributions. The well-posedness of the direct source problem is established in the distribution sense. The micro-correlation strength of the random source, which appears to be the strength in the principal symbol of the covariance operator, is proved to be uniquely determined by the wave field in an open measurement set. Numerical experiments are presented for the white noise model to demonstrate the validity and effectiveness of the proposed method.
Multidimensional hydrogenic states: position and momentum expectation values
Authors: Dehesa J S , Puertas-Centeno D 
Published: November 2020

Abstract
The position and momentum probability densities of a multidimensional quantum system are fully characterized by means of the radial expectation values ⟨r

α
⟩ and

p

α

, respectively. These quantities, which describe and/or are closely related to various fundamental properties of realistic systems, have not been calculated in an analytical and effective manner up until now except for a number of three-dimensional hydrogenic states. In this work we explicitly show these expectation values for all discrete stationary D-dimensional hydrogenic states in terms of the dimensionality D, the strength of the Coulomb potential (i.e. the nuclear charge) and the D state’s hyperquantum numbers. Emphasis is placed on the momentum expectation values (mostly unknown, specially the ones with odd order) which are obtained in a closed compact form. Applications are made to circular, S-wave, high-energy (Rydberg) and high-dimensional (pseudo-classical) states of three- and multidimensional hydrogenic atoms. This has been possible because of the analytical algebraic and asymptotical properties of the special functions (orthogonal polynomials, hyperspherical harmonics) which control the states’ wavefunctions. Finally, some Heisenberg-like uncertainty inequalities satisfied by these dispersion quantities are also given and discussed.
Nucleon-nucleus optical potential computed with the Gogny interaction
Authors: Lopez-Moraña Juan , Viñas Xavier 
Published: November 2020

Abstract
The ability of the Gogny forces of the D1 family to describe the nucleon-nucleus scattering is studied. To this end, we use an optical model (OM) potential built up using a semi-microscopic nuclear matter (NM) approach. The real and imaginary parts of the OM are provided by the first and second-order terms, respectively, of the Taylor expansion of the mass operator calculated within the Brueckner–Hartree–Fock (BHF) method using the reaction G-matrix built up with the effective Gogny force instead of a microscopic interaction. The optical potential in finite nuclei is obtained through the local density approximation (LDA) using the neutron and proton densities provided by a quasi-local Hartree–Fock (HF) calculation with the same Gogny force for the sake of consistency. A reasonable good agreement is found between the theoretical differential cross-sections and the analyzing powers (AP) of the elastic neutron and proton scattering along the periodic table from Ca to Pb calculated with the Gogny forces and the corresponding values predicted by the global phenomenological potential of Koning and Delaroche. To investigate the limits of the approximations used in this work, comparisons with the results of nucleon-nucleus elastic scattering in 40Ca and 48Ca obtained using the nuclear structure model (NSM) are also performed.
A continuous dynamic recrystallization constitutive model combined with grain fragmentation and subgrain rotation for aluminum alloy 2219 under hot deformation
Authors: Gan Tian , Yu Zhongqi , Zhao Yixi , Fan Xiaoguang , Lai Xinmin 
Published: November 2020

Abstract
The large temperature gradient resulted from rapid heat dissipation and a long process period in the hot deformation of aluminum alloy causes complex microstructure evolutions. Accurate constitutive models describing the evolution of the microstructures over a wide temperature range are acquired. Thus, a physically-based continuous dynamic recrystallization constitutive model combined with grain fragmentation and subgrain rotation was established in this investigation. Uniaxial hot compression tests for aluminum alloy 2219 were conducted at temperatures of 250 °C–450 °C and the evolution of microstructures were analyzed via metallographic technique. Then internal state variables were proposed to describe the migration of grain boundary, dislocation density, average grain boundary misorientation, and subgrain/grain size. The net torque on the grain is introduced to precisely describe the progressive subgrain rotation mechanism. Moreover, geometrically necessary dislocations are considered to reasonably simulate the rise in flow stress associated with grain fragmentation. The results show that continuous dynamic recrystallization (CDRX) and dynamic recovery are the main softening mechanisms. The CDRX mechanism is gradually changed from grain fragmentation to subgrain rotation due to the increase in temperature. The new constitutive model may precisely predict the flow stresses, subgrain/grain size, and average misorientation in the wide temperature range. Comparing with the existing continuous dynamic recrystallization model which only considers subgrain rotation, the overestimate of the grain size in the low-temperature range is avoided in the new constitutive model. Furthermore, the contributions of the grain fragmentation to the increase in strain hardening can reasonably be covered.
Physics approaches to the spatial distribution of immune cells in tumors
Authors: Yu Clare C , Wortman Juliana C , He Ting-Fang , Solomon Shawn , Zhang Robert Z , Rosario Anthony , Wang Roger , Tu Travis Y , Schmolze Daniel , Yuan Yuan , Yost Susan E , Li Xuefei , Levine Herbert , Atwal Gurinder , Lee Peter P 
Published: November 2020

Abstract
The goal of immunotherapy is to mobilize the immune system to kill cancer cells. Immunotherapy is more effective and, in general, the prognosis is better, when more immune cells infiltrate the tumor. We explore the question of whether the spatial distribution rather than just the density of immune cells in the tumor is important in forecasting whether cancer recurs. After reviewing previous work on this issue, we introduce a novel application of maximum entropy to quantify the spatial distribution of discrete point-like objects. We apply our approach to B and T cells in images of tumor tissue taken from triple negative breast cancer patients. We find that the immune cells are more spatially dispersed in good clinical outcome (no recurrence of cancer within at least 5 years of diagnosis) compared to poor clinical outcome (recurrence within 3 years of diagnosis). Our results highlight the importance of spatial distribution of immune cells within tumors with regard to clinical outcome, and raise new questions on their role in cancer recurrence.
Single-site-resolved imaging of ultracold atoms in a triangular optical lattice
Authors: Yamamoto Ryuta , Ozawa Hideki , Nak David C. , Nakamura Ippei , Fukuhara Takeshi 
Published: November 2020

Abstract
We demonstrate single-site-resolved fluorescence imaging of ultracold 87Rb atoms in a triangular optical lattice by employing Raman sideband cooling. Combining a Raman transition at the D1 line and a photon scattering through an optical pumping of the D2 line, we obtain images with low background noise. The Bayesian optimisation of 11 experimental parameters for fluorescence imaging with Raman sideband cooling enables us to achieve single-atom detection with a high fidelity of (96.3 ± 1.3)%. Single-atom and single-site resolved detection in a triangular optical lattice paves the way for the direct observation of spin correlations or entanglement in geometrically frustrated systems.
Digital quantum simulation framework for energy transport in an open quantum system
Authors: Gupta Pragati , Chandrashekar C M 
Published: November 2020

Abstract
Quantum effects such as the environment assisted quantum transport (ENAQT) displayed in photosynthetic Fenna–Mathews–Olson (FMO) complex has been simulated on analog quantum simulators. Digital quantum simulations offer greater universality and flexibility over analog simulations. However, digital quantum simulations of open quantum systems face a theoretical challenge; one does not know the solutions of the continuous time master equation for developing quantum gate operators. We give a theoretical framework for digital quantum simulation of ENAQT by introducing new quantum evolution operators. We develop the dynamical equation for the operators and prove that it is an analytical solution of the master equation. As an example, using the dynamical equations, we simulate the FMO complex in the digital setting, reproducing theoretical and experimental evidence of the dynamics. The framework gives an optimal method for quantum circuit implementation, giving a log reduction in complexity over known methods. The generic framework can be extrapolated to study other open quantum systems.
Dynamics rate of fiber chemical etching: new partial removal of cladding technique for humidity sensing application
Authors: Riza Muhammad Arif , Go Yun Ii , Maier Robert R J 
Published: November 2020

Abstract
Sensor-based optical fibers require thinner cladding for enhanced interaction between the evanescence wave and the environment. Fiber Bragg grated fiber sensors relying on an axial strain require chemical etching to weaken the fiber allowing more sensitivity in terms of strain. Ease of sensor multiplexing can be achieved through etching the mid-section of the fiber which is rarely reported with a custom-made holder. This paper proposes a technique for etching at the middle section of a fiber with a custom fiber holder. Chemical etching of a single-mode silica fiber was done with 48% hydrofluoric acid (HF). Etching proceeds until the fiber was completely etched. The optical spectrum was recorded at an interval of 3 min. Microscope visuals indicated possible etching with the mount design until ∼10 μm at 45 min with the fiber intact compared to a longer etching time. A longer etching duration than 45 min results in the optical spectrum displaying a null spectrum, depicting core damage. Etching of the fiber follows a linear trend and the reaction rate was determined to be 1.699 μm min−1 experimentally. The proposed fiber holder and receptacle were capable of etching a fiber with minimal defects while maintaining the ease of fiber handling.
Multiphoton microscopy imaging analysis: non-destructive inspection for the cornea
Authors: Lin Si-Le , Hao Si-Yang 
Published: November 2020

Abstract
Multiphoton microscopy (MPM) can create high penetration depth, low photodamage, real-time and 3-dimensional-tissue subcellular resolution images of the cornea. It surmounts the difficulty of non-destructive or in vivo detection caused by the sensitivity of the cornea. The emerging technology overcomes the high photodamage and low image contrast of general optical inspection by using nonlinear optical processes. Different chemical composition in the cornea excites diverse up-conversion photons to form the image and spectra, providing accurate and comprehensive information of the cornea. MPM, which combines the advantages of optical imaging and spectral measurement technique, provides the detection of metabolic, cell density, keratitis, drug delivery, corneal thickness, intraocular pressure, and fiber orientation of the cornea. We review the state of the art of MPM imaging analysis studies and discuss prospects.
Enhancement of quantum entanglement by local non-Hermitian operation under various decoherence sources
Authors: Wang Qiong , Xu Lan , He Zhi 
Published: November 2020

Abstract
We examine the validity and limitation of the local non-Hermitian operation in the enhancement of qubit-qubit entanglement from various decoherence sources. We derive the exact expressions of concurrence quantifying entanglement for an exactly solving model consisting of two qubits interacting with various decoherence sources. we show explicitly that the local non-Hermitian operation indeed helps for enhancing quantum entanglement from amplitude damping, but not for phase damping. Finally, we give a brief discussion of the physical explanation for our scheme.
Nonlinear beam shaping in periodical χ
(2) fork gratings with structural defects
Authors: Xu Tian Xiang , Zhao Ru Wei , Dai Shi Xun 
Published: November 2020

Abstract
Nonlinear beam shaping provides an efficient way to control the phase and amplitude of optical waves while shifting their frequency. Periodical topological structures with a modulated second-order nonlinear optical coefficient (χ
(2)) are commonly used to generate special optical beams at new frequencies, e.g. the second harmonic vortices. In this paper, we theoretically study the influence of structural imperfection on nonlinear beam shaping and demonstrate how to utilize these imperfections for second harmonic generation with controlled orbital angular momentums. The results indicate that the studied nonlinear beam-shaping process has excellent tolerance to structural defects, and introducing designed defects of different scales and shapes constitutes a flexible approach for controlling the orbital angular momentum of light at new frequencies. As a proof of concept example, the nested χ
(2) structures are designed for generating optical vortices with predesigned topological charges along different directions. In addition, the performance of the nonlinear generation of vortex beams with a fundamental beam shifted from the center of the fork grating is also discussed. The study opens up new prospects for the optimization of nonlinear χ
(2) structures for special beam generation at new frequencies.
A modification of Faddeev–Popov approach free from Gribov ambiguity
Authors: Chen Chong-yao , Gao Fei , Liu Yu-Xin 
Published: November 2020

Abstract
We propose a modified version of the Faddeev–Popov (FP) quantization approach for non-Abelian gauge field theory to avoid Gribov ambiguity. We show that by means of introducing a new method of inserting the correct identity into the Yang–Mills generating functional and considering the identity generated by an integral through a subgroup of the gauge group, the problem of Gribov ambiguity can be removed naturally. Meanwhile by handling the absolute value of the FP determinant with the method introduced by Williams and collaborators, we lift the Jacobian determinant together with the absolute value and obtain a local Lagrangian. The new Lagrangian will have a nilpotent symmetry which can be viewed as an analog of the Becchi–Rouet–Stora–Tyutin symmetry.
Energy level splitting of a 2D hydrogen atom with Rashba coupling in non-commutative space
Authors: Aghababaei S , Rezaei G 
Published: November 2020

Abstract
We explore the non-commutative (NC) effects on the energy spectrum of a two-dimensional hydrogen atom. We consider a confined particle in a central potential and study the modified energy states of the hydrogen atom in both coordinates and momenta of non-commutativity spaces. By considering the Rashba interaction, we observe that the degeneracy of states can also be removed due to the spin of the particle in the presence of NC space. We obtain the upper bounds for both coordinates and momenta versions of NC parameters by the splitting of the energy levels in the hydrogen atom with Rashba coupling. Finally, we find a connection between the NC parameters and Lorentz violation parameters with the Rashba interaction.
Analyses of multi-pion Bose-Einstein correlations for granular sources with coherent pion-emission droplets *
Authors: Bary Ghulam , Zhang Wei-Ning , Ru Peng , Yang Jing 
Published: November 2020

Abstract
The ALICE Collaboration measured three- and four-pion Bose-Einstein correlations (BECs) for Pb-Pb collisions at the Large Hadron Collider (LHC). It is speculated that the observed significant suppression of multi-pion BECs is owing to a considerable degree of coherent pion emission in these collisions. Here, we study multi-pion BEC functions for granular sources with coherent pion-emission droplets. We find that the intercepts of the multi-pion correlation functions at the relative momenta near zero are sensitive to the number of droplets in the granular source. They decrease with the droplet number. The three-pion correlation functions for evolving granular sources with momentum-dependent partially coherent pion-emission droplets basically agree with the experimental data for Pb-Pb collisions at

TeV at the LHC. However, the model results for the four-pion correlation function are inconsistent with the experimental data. Investigations into normalized multi-pion correlation functions of granular sources suggest an interesting enhancement of the normalized four-pion correlation function in the moderate relative-momentum region.
Charmed and ϕ meson decay constants from 2+1-flavor lattice QCD *
Authors: Chen Ying , Chiu Wei-Feng , Gong Ming , Liu Zhaofeng , Ma Yunheng 
Published: November 2020

Abstract
On a lattice with 2+1-flavor dynamical domain-wall fermions at the physical pion mass, we calculate the decay constants of

,

, and

. The lattice size is

, which corresponds to a spatial extension of

fm, with a lattice spacing of

fm. For the valence light, strange, and charm quarks, we use overlap fermions at several mass points close to their physical values. Our results at the physical point are

MeV,

MeV,

MeV,

MeV, and

MeV. The couplings of

and

to the tensor current (

) can be derived from ratios

and

, respectively, which are the first lattice quantum chromodynamics (QCD) results. We also obtain ratios

and

, which reflect the size of heavy quark symmetry breaking in charmed mesons. Ratios

and

can be taken as a measure of SU(3) flavor symmetry breaking.
A new correction method for quasi-Keplerian orbits
Authors: Chen Yue , Ma Da-Zhu , Xia Fang 
Published: November 2020

Abstract
A pure two-body problem has seven integrals including the Kepler energy, the Laplace vector and the angular momentum vector. However, only five of them are independent. When the five independent integrals are preserved, the two other dependent integrals are naturally preserved from a theoretical viewpoint; but they may not necessarily be from a numerical computational viewpoint. Because of this, we use seven scale factors to adjust the integrated positions and velocities so that the adjusted solutions strictly satisfy the seven constraints. Noticing the existence of the two dependent integrals, we adopt the Newton iterative method combined with singular value decomposition to calculate these factors. This correction scheme can be applied to perturbed two-body and N-body problems in the solar system. In this case, the seven quantities associated with each planet slowly vary with time. More accurate values can be given to the seven slowly-varying quantities by integrating the integral invariant relations of these quantities and the equations of motion. They should be satisfied with the adjusted solutions. Numerical tests show that the new method can significantly reduce the rapid growth of numerical errors for all orbital elements.
Direct determination of midplane background neutral density profiles from neutral particle analyzers
Authors: Bogar K. , Geiger B. , Schneider P.A. , Jansen van Vuuren A. , Grover O. , ASDEX Upgrade team the , EUROfusion MST1 team the 
Published: November 2020

Abstract
Here we present a new method that allows the determination of background neutral density profiles based on measurements from neutral particle analyzers (NPA). Bayesian optimization is used to obtain a reliable 5-parameter representation of the inferred profiles. The method has been benchmarked using forward modelling from FIDASIM against measured data. The systematic errors coming from assumptions made in the analysis were evaluated and they are lower than ≲5%. The new method has been tested using data from the ASDEX Upgrade tokamak. When using reconstructed neutral density profiles, good agreement is found between the measured NPA fluxes of neutralized fast ions with predictions based on TRANSP and FIDASIM. Moreover, a clear drop of neutral density is observed at the plasma boundary after edge localized mode (ELM) activity. As suggested by KN1D simulations, this drop is mainly due to an increase of scrape-off layer (SOL) ionization rate, resulting from higher SOL plasma densities and temperatures after the ELM crash. Moreover, the new method allows calculating the local plasma ionization source which will be important for future transport studies.
Tokamak discharge simulation coupling free-boundary equilibrium and plasma model with application to JT-60SA
Authors: Ostuni V. , Artaud J.F. , Giruzzi G. , Joffrin E. , Heumann H. , Urano H. 
Published: November 2020

Abstract
In order to simulate a full tokamak discharge, a fast integrated tokamak modeling tool for scenario design, METIS, is coupled with a quasi-static free-boundary magnetic equilibrium code, FEEQS. The first code is able to compute at each time the plasma equilibrium, the current density and plasma pressure profiles. The generated outputs are iteratively used by the second code that computes the poloidal field coils currents needed in order to obtain a given plasma shape. This is used to assess the feasibility of scenarios designed by integrated modeling simulations. This approach is much faster with respect to full simulators, equipped with specific feedback controllers, and can be regarded as complementary or preparatory to much more time-consuming scenario control optimisation. The results obtained with the equilibrium code are benchmarked with data already available and computed using the TOSCA code. To illustrate how the coupled codes work, the optimization of one of the reference scenarios of the JT-60SA tokamak is carried out. The use of this new simulation tool for tokamak scenario design is discussed.