A “Hard to Die” Series Expansion and Lucas Polynomials of the Second Kind

We show how to use the Lucas polynomials of the second kind in the solution of a homogeneous linear differential system with constant coefficients, avoiding the Jordan canonical form for the relevant matrix.

Entropy and Cosmological Constant of a Universe Calculated by Means of Dimensional Analysis, Margolus-Levitin Theorem and Landauer’s Principle

By means of the dimensional analysis a spherically simmetric universe with a mass M = c3/(2HG) and radius equal to c/H is considered, where H is the Hubble constant, c the speed of light and G the Newton gravitational constant. The density corresponding to this mass is equal to the critical density ρcr = 3H2/(8πG). This universe evolves according to a Bondi-Gold-Hoyle scenario, with continuous creation of matter at a rate such to maintain, during the expansion, the density always critical density. Using the Margolus-Levitin theorem and the Landauer’s principle, an entropy is associated with this universe, obtaining a formula having the same structure as the Bekenstein-Hawking formula of the entropy of a black hole. Furthermore, a time-dependent cosmological constant Λ, function of the Hubble constant and the speed of light, is proposed.

Comparison of Proton Shower Developments in the BGO Calorimeter of the Dark Matter Particle Explorer between GEANT4 and FLUKA Simulations

The DArk Matter Particle Explorer(DAMPE)is a satellite-borne detector for high-energy cosmic rays and y-rays.To fully understand the detector performance and obtain reliable physical results,extensive simulations of the detector are necessary.The simulations are particularly important for the data analysis of cosmic ray nuclei,which relies closely on the hadronic and nuclear interactions of particles in the detector material.Widely adopted simulation softwares include the GEANT4 and FLUKA,both of which have been implemented for the DAMPE simulation tool.Here we describe the simulation tool of DAMPE and compare the results of proton shower properties in the calorimeter from the two simulation softwares.Such a comparison gives an estimate of the most significant uncertainties of our proton spectral analysis.

Calibration of the DAMPE Plastic Scintillator Detector and its on-orbit performance

The DArk Matter Particle Explorer(DAMPE) is a space-borne apparatus for detecting the highenergy cosmic-ray-like electrons, γ-rays, protons and heavy ions. The Plastic Scintillator Detector(PSD)is the top-most sub-detector of the DAMPE. The PSD is designed to measure the charge of incident highenergy particles and it also serves as a veto detector for discriminating γ-rays from charged particles. In this paper, a PSD on-orbit calibration procedure is described, which includes the five steps of pedestal, dynode correlation, response to minimum-ionizing particles, light attenuation function and energy reconstruction.A method for reconstructing the charge of incident high energy cosmic-ray particles is introduced. The detection efficiency of each PSD strip is verified to be above 99.5%; the total efficiency of the PSD for charged particles is above 99.99%.

Solution of Linear Dynamical Systems Using Lucas Polynomials of the Second Kind

The use of functions, expressible in terms of Lucas polynomials of the second kind, allows us to write down the solution of linear dynamical systems—both in the discrete and continuous case—avoiding the Jordan canonical form of involved matrices. This improves the computational complexity of the algorithms used in literature.

Generalized Lagrange Structure of Deformed Minkowski Spacetime

We discuss the generalized Lagrange structure of a deformed Minkowski space (DMS), , namely a (four-dimensional) generalization of the (local) space-time based on an energy-dependent “deformation” of the usual Minkowski geometry. In , local Lorentz invariance is naturally violated, due to the energy dependence of the deformed metric. Moreover, the generalized Lagrange structure of allows one to endow the deformed space-time with both curvature and torsion.

Exploring the enigmatic interplay between polymers and nanoparticles in a non-Newtonian viscoelastic fluid

Non-Newtonian fluids have variable viscosity in response to shear rate,and the presence of polymers and nanoparticles further modifies their flow characteristics.In this paper,the effects of polymers and nanoparticles on mass and heat transfer control,drag reduction,boundary layer flow development in a polymeric finitely extensible nonlinear elastic-Peterlin(FENE-P)fluid,and the significance of nanoscience in modern day life are discussed.We examine the behavior of polymer additives by utilizing a dispersion model in conjunction with the polymeric FENE-P model.Our work includes a comparison with Cortell's earlier work,which only looked at the behavior of polymer’s inclusion into the base fluid.This research investigates numerically how the inclusion of polymers and nanoparticles into the base fluid reduces drag while increasing heat and mass transfer.The observed variations in skin friction,reduced Nusselt,and Sherwood numbers indicate an intriguing correlation between the rates of heat and mass transport and surface drag.More precisely,as the heat and mass transfer efficiency improve,the surface encounters less resistance,which is commonly referred to as drag.In summary,the research highlights the capability of polymers and nanoparticles to effectively modify fluid dynamics,minimize drag,and enhance mass and heat transfer inside the flow region.

Glassy dynamics of water at interface with biomolecules: A Mode Coupling Theory test

We study the slow dynamics of hydration water upon cooling in two different biological aqueous solutions,one containing a molecule of lysozyme and another with trehalose molecules.In particular we test if the glassy behaviour of these solutions fulfils the predictions of the popular Mode Coupling Theory of glassy dynamics.In particular we test the Time Temperature Superposition Principle and the matching of the exponents of the theory.Our results confirm that this theory is able to describe the dynamical behaviour of supercooled water also in non ideal cases as the ones under investigation in the region of mild supercooling.

Energy spectrum of cosmic protons and helium nuclei by a hybrid measurement at 4300 m a.s.l.

The energy spectrum of cosmic Hydrogen and Helium nuclei has been measured below the so-called ＂knee＂ by using a hybrid experiment with a wide field-of-view Cherenkov telescope and the Resistive Plate Chamber （RPC） array of the ARGO-YBJ experiment at 4300 m above sea level. The Hydrogen and Helium nuclei have been well separated from other cosmic ray components by using a multi-parameter technique. A highly uniform energy resolution of about 25% is achieved throughout the whole energy range （100-700 TeV）. The observed energy spectrum is compatible with a single power law with index γ=-2.63±0.06.

Fragile to strong crossover and Widom line in supercooled water： A comparative study

The aim of this paper is to discuss the relationship between the dynamics and thermodynamics of water in the supercooled region. Reviewed case studies comprehend bulk water simulated with the SPC/E, TIP4P and TIP4P/2005 potentials, water at protein interfaces, and water in solution with electrolytes. Upon supercooling, the fragile to strong crossover in the s-relaxation of water is found to occur when the Widom line emanating from the liquid-liquid critical point is crossed. This appears to be a general characteristic of supercooled water, not depending on the applied interaction potential and/or different local environments.

High-speed flow of interacting organic polaritons

The strong coupling of an excitonic transition with an electromagnetic mode results in composite quasi-particles called exciton polaritons,which have been shown to combine the best properties of their individual components in semiconductor microcavities.However,the physics and applications of polariton flows in organic materials and at room temperature are still unexplored because of the poor photon confinement in such structures.Here,we demonstrate that polaritons formed by the hybridization of organic excitons with a Bloch surface wave are able to propagate for hundreds of microns showing remarkable third-order nonlinear interactions upon high injection density.These findings pave the way for the study of organic nonlinear light–matter fluxes and for a technologically promising route of the realization of dissipation-less on-chip polariton devices operating at room temperature.

Shifts in the BCFW method for QED

We study the application of BCFW recursion relations to the QED process 0→e^(-)e^(+)nγ.Based on 6-point amplitudes(both MHVA and NMHVA)computed from Feynman diagrams in the Berends-Giele gauge,we conduct a comprehensive study on different shifts.Subsequently,we propose a new shift(LLYZ shift),which can lead to the full amplitudes of these processes and have several realistic computational advantages.We compare the number of terms and independent amplitudes of this novel shift with those of a few typical shifts.

Characterisation of Photocathodes Based on Pb Thin Film Deposited by UV Pulsed Laser Ablation

This work deals with the deposition of lead （Pb） thin films by the UV pulsed laser ablation technique, for their further use as photocathode devices in superconducting radio frequency guns. Scanning electron microscopy and atomic force microscopy analyses were performed to study the morphological features of Pb thin films deposited on Si （100） and Nb substrates. The films showed a granular structure with a nearly fully covered surface only for that one deposited on Nb substrate. X-ray diffraction measurements indicate the growth of polycrystalline Pb thin films with a preferential orientation along （111） planes. Results of the photoemission performance of Pb thin film deposited on Nb substrate showed a very encouraging average value of quantum efficiency of 6 x 10-5 through a single-photon absorption process, promoting further studies in the realisation of Pb photocathodes by this technique.

Majorana Representations of Finite Groups

In this paper we give a brief overview of the theory of Majorana representations of finite groups.

Groups with Finitely Many Homomorphic Images of Finite Rank

A group is called a Cernikov group if it is abelian-by-finite and satisfies the minimal condition on subgroups. A new characterization of Cernikov groups is given here, by proving that in a suitable large class of generalised soluble groups they coincide with the groups having only finitely many homomorphic images of finite rank （up to isomorphisms） and admitting an ascending normal series whose factors have finite rank.

Quantum hydrodynamics of a single particle

Semiconductor devices are strong competitors in the race for the development of quantum computational systems.In this work,we interface two semiconductor building blocks of different dimensionalities with complementary properties:(1)a quantum dot hosting a single exciton and acting as a nearly ideal single-photon emitter and(2)a quantum well in a 2D microcavity sustaining polaritons,which are known for their strong interactions and unique hydrodynamic properties,including ultrafast real-time monitoring of their propagation and phase mapping.In the present experiment,we can thus observe how the injected single particles propagate and evolve inside the microcavity,giving rise to hydrodynamic features typical of macroscopic systems despite their genuine intrinsic quantum nature.In the presence of a structural defect,we observe the celebrated quantum interference of a single particle that produces fringes reminiscent of wave propagation.While this behavior could be theoretically expected,our imaging of such an interference pattern,together with a measurement of antibunching,constitutes the first demonstration of spatial mapping of the self-interference of a single quantum particle impinging on an obstacle.

Accretion in strong field gravity with eXTP

In this paper we describe the potential of the enhanced X-ray Timing and Polarimetry(eXTP) mission for studies related to accretion flows in the strong field gravity regime around both stellar-mass and supermassive black-holes. eXTP has the unique capability of using advanced "spectral-timing-polarimetry" techniques to analyze the rapid variations with three orthogonal diagnostics of the flow and its geometry, yielding unprecedented insight into the inner accreting regions, the effects of strong field gravity on the material within them and the powerful outflows which are driven by the accretion process.

Observatory science with eXTP

In this White Paper we present the potential of the enhanced X-ray Timing and Polarimetry(eXTP) mission for studies related to Observatory Science targets. These include flaring stars, supernova remnants, accreting white dwarfs, low and high mass X-ray binaries, radio quiet and radio loud active galactic nuclei, tidal disruption events, and gamma-ray bursts. eXTP will be excellently suited to study one common aspect of these objects: their often transient nature. Developed by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Science, the eXTP mission is expected to be launched in the mid 2020s.

Measurement of the integrated luminosity of the Phase 2 data of the Belle Ⅱ experiment

From April to July 2018,a data sample at the peak energy of the T(4 S) resonance was collected with the Belle Ⅱ detector at the SuperKEKB electron-positron collider.This is the first data sample of the Belle Ⅱ experiment.Using Bhabha and digamma events,we measure the integrated luminosity of the data sample to be(496.3±0.3±3.0) pb-1,where the first uncertainty is statistical and the second is systematic.This work provides a basis for future luminosity measurements at Belle Ⅱ.