Physical Parameter Space Research Articles

Low-Stress State of Simply-Supported Anisotropic Composite Plates

The stress state in the neighborhood of the common edge of a simply-supported composite wedge-shaped plate under transverse load has been studied. The materials of the constituent plates are cylindrically orthotropic. The problem is solved using the classical theory of anisotropic plates. Equations are derived for a hypersurface which, in the space of physical and geometric parameters, is the boundary of the region of parameters for which the neighborhood of the common edge of the composite plate is in a low-stress state (the stresses at the points of the common edge of the composite plate are limited).

Gyrokinetic analysis of radial dependence and global effects on the zero particle flux condition in a TCV plasma

In small-sized tokamaks, finite Larmor radius effects could lead to a significant discrepancy between gyrokinetic local flux-tube results and global ones. This has been highlighted by previous turbulent transport studies as in McMillan et al (2010 Phys. Rev. Lett.). The impact of such effects on the zero particle flux condition is investigated here. The zero particle flux condition is useful to estimate the density peaking, reducing the uncertainty on physical input parameters derived from experimental measurements, for cases where the particle source is negligible. This constraint has been applied to the analysis of a particular TCV discharge, where a detailed reconstruction of the zero particle flux hyper-surface in the multidimensional physical parameter space at fixed radius had been presented in Mariani et al (2018 Phys. Plasmas). Here, we extend these results, investigating their radial dependence, together with the impact of global effects. These so-called ρ* effects are analyzed by simulating a plasma annulus corresponding to the stiff region . Because of the computational cost of the nonlinear global gyrokinetic simulations, we restrict to a two species plasma in the collisionless regime, with heavy electrons and simplified density and temperature radial profiles. With these simplifications, the results seem to point towards global effects on the zero particle flux condition being relatively weak.

Constraint Equations of Physical and Geometrical Parameters of an Arbitrary Branched Hydraulic System of the General Form

The development trends of aviation technology impose stringent requirements for the quality of aircraft design in general and its onboard power systems in particular. The article considers an arbitrary branched hydraulic system of the aircraft. With known output characteristics of the hydraulic system, i.e. the function that it must perform, the internal parameters of the system that provide efficient flow distribution required for the calculated operation of the mechanisms are determined. The problem of obtaining a system of equations of the general form linking the physical parameters of the hydraulic system, such as supply power, pressure in consumers and flow rate in all functional subsystems, with the geometric parameters of the pipelines and consumers of the system is solved by an analytical method. The equations in the resulting system are considered in the space of physical parameters. As the geometric parameters of the elements are not specified in an explicit form, it allows the authors to obtain the only unique solution for an arbitrary number of pipelines and consumers, excluding an iterative process. Besides, the final equations clearly determine the most effective mode of operation of the power supply.

Prediction of robust chaos in micro and nanoresonators under two-frequency excitation.

Robust chaos in a dynamical system is characterized by the persistence of the chaotic attractor with changes in the system parameters and is generally required in practical applications based upon physical sources of chaos. However, for applications that rely upon continuous time chaotic signals, there are now very few alternatives of dynamical systems with robust chaos that could be used. In this context, it is important to find a new dynamical system and, particularly, new physical systems that present robust chaos. In this work, we show through simulations that a relevant physical system, suspended beam micro and nanoelectromechanical resonators, can present robust chaos when excited by two distinct frequencies. To demonstrate the existence of robust chaos in the system, we perform an extensive numerical analysis, showing that the attractor is unique and changes smoothly in a large region of the relevant physical parameter space. We find that the robustness of the chaotic dynamics depends crucially on the dissipation, which must be sufficiently small. When the dissipation is small, we find a large range of frequencies, frequency ratios, and applied voltages where robust chaos is observed. These findings turn these systems into viable and strong candidates for practical applications since the chaotic dynamics becomes quite insensitive to fabrication tolerances, changes in the physical parameters induced by the environment, and aging.

A composite pNGB leptoquark at the LHC

The measurements of RK(∗) and RD(∗) by BaBar, Belle and the LHCb collaborations could be showing a hint of lepton flavor universality violation that can be accommodated by the presence of suitable leptoquarks at the TeV scale. We consider an effective description, with leptoquarks arising as composite pseudo Nambu-Goldstone bosons, as well as anarchic partial compositeness of the SM fermions. Considering the RK(∗) anomaly within this framework, we study pair production of {S}_3sim {left(overline{3},3right)}_{1/3} at the LHC. We focus on the component S31/3 of the triplet, which decays predominantly into tτ and bν, and study the bounds from existing searches at sqrt{s}=13 TeV at the LHC. We find that sbottom searches in the boverline{b}+{E}_{mathrm{T}}^{mathrm{miss}} final state best explore the region in parameter space preferred by our model and currently exclude S31/3 masses up to ∼1 TeV. Additional searches, considering the tτ and tμ decay modes, are required to probe the full physical parameter space. In this paper we also recast existing studies on direct leptoquark searches in the tτ tτ channel and SM toverline{t}toverline{t} searches, and obtain the regions in parameter space currently excluded. Practically the whole physical parameter space is currently excluded for masses up to ∼0.8 TeV, which could be extended up to ∼1 TeV with the full Run 3 dataset. We conclude that pair production searches for this leptoquark can benefit from considering the final state tτ b + ETmiss, where the largest branching ratio is expected. We appraise that future explorations of leptoquarks explaining the B-anomalies with masses beyond the TeV should also consider single and non-resonant production in order to extend the mass reach.

Y Dwarf Trigonometric Parallaxes from the Spitzer Space Telescope

Abstract Y dwarfs provide a unique opportunity to study free-floating objects with masses <30 M Jup and atmospheric temperatures approaching those of known Jupiter-like exoplanets. Obtaining distances to these objects is an essential step toward characterizing their absolute physical properties. Using Spitzer’s Infrared Array Camera (IRAC) [4.5] images taken over baselines of ∼2–7 years, we measure astrometric distances for 22 late-T and early Y dwarfs, including updated parallaxes for 18 objects and new parallax measurements for 4 objects. These parallaxes will make it possible to explore the physical parameter space occupied by the coldest brown dwarfs. We also present the discovery of six new late-T dwarfs, updated spectra of two T dwarfs, and the reclassification of a new Y dwarf, WISE J033605.04−014351.0, based on Keck/NIRSPEC J-band spectroscopy. Assuming that effective temperatures are inversely proportional to absolute magnitude, we examine trends in the evolution of the spectral energy distributions of brown dwarfs with decreasing effective temperature. Surprisingly, the Y dwarf class encompasses a large range in absolute magnitude in the near- to mid-infrared photometric bandpasses, demonstrating a larger range of effective temperatures than previously assumed. This sample will be ideal for obtaining mid-infrared spectra with the James Webb Space Telescope because their known distances will make it easier to measure absolute physical properties.

Existence of electron acoustic solitary waves in relativistic limit

The nonlinear relativistic dynamics of electron acoustic waves (EAWs) in collisionless, unmagnetized plasma comprising cold inertial electrons, hot Boltzmann distributed electrons, and stationary ions are studied. The Sagdeev pseudopotential technique is employed to discuss the effect of equilibrium plasma species density and temperature of the hot electrons on the relativistic solitary wave solutions. In exploring the electron acoustic soliton characteristics, we encounter only negative polarity solitons which are found to exist in a restricted range of the physical parameter space of the system. In addition, we extend our analysis to demonstrate the wave breaking phenomena of EAW and estimate the maximum sustainable electric field amplitude of this mode considering the relativistic electron mass variation effect.

Bifurcation and singularity analysis of HSLDS vibration isolation system with elastic base

In order to reveal the bifurcation mechanism and optimize the system design for high-static-low-dynamic-stiffness (HSLDS) vibration isolation system (VIS) with elastic base, the local bifurcation analyses both in unfolding parameter space and physical parameter space were carried out theoretically and numerically. Firstly, the restoring force of the HSLDS-VIS was approximated to linear and cubic stiffness by applying the Maclaurin series expansion and the motion equations of HSLDS-VIS with elastic base were established. Subsequently, the motion equations of HSLDS-VIS with elastic base were formulated to transform the system into a standard form and the averaging method was applied to obtain the single-variable bifurcation equation for the HSLDS-VIS with elastic base in case of primary resonance and 1:2 internal resonance. Furthermore, the transition sets and bifurcation diagrams in the unfolding parameter space were studied by means of singularity theory. Finally, for the engineering application, the transition sets were transferred back to the physical parameter space, thus to obtain the bifurcation diagrams of the amplitude with respect to the external force. The numerical simulation results show that the local bifurcations of HSLDS-VIS with elastic base in case of 1:2 internal resonance are considerable complex and need to be analyzed in six two-parameters spaces, meanwhile, the necessary condition of multiple solutions lies in some physical parameters, which can provide a theoretical basis and reference for design and application of the HSLDS-VIS with elastic base.

The GALAH survey and Gaia DR2: (non-)existence of five sparse high-latitude open clusters

Sparse open clusters can be found at high galactic latitudes where loosely populated clusters are more easily detected against the lower stellar background. Because most star formation takes place in the thin disk, the observed population of clusters far from the Galactic plane is hard to explain. We combined spectral parameters from the GALAH survey with the Gaia DR2 catalogue to study the dynamics and chemistry of five old sparse high-latitude clusters in more detail. We find that four of them (NGC 1252, NGC 6994, NGC 7772, NGC 7826) - originally classified in 1888 - are not clusters but are instead chance projections on the sky. Member stars quoted in the literature for these four clusters are unrelated in our multi-dimensional physical parameter space; the published cluster properties are therefore irrelevant. We confirm the existence of morphologically similar NGC 1901 for which we provide a probabilistic membership analysis. An overdensity in three spatial dimensions proves to be enough to reliably detect sparse clusters, but the whole 6-dimensional space must be used to identify members with high confidence, as demonstrated in the case of NGC 1901.

Single-top production and rare top interactions

The study of the top quark's properties is an important part of the LHC programme. In earlier work, we have studied the rare decay $t \to b \bar b c$, using effective operators to capture the effects of physics beyond the Standard Model. However top decay is primarily sensitive to new physics in the sub-TeV energy regime. If this new physics resides at a higher energy scale, then one needs to turn to single-top production. In this paper, we use the $s$-channel and $t$-channel single-top production measurements to constrain the new physics parameter space associated with such contact interactions. We also study the net top polarization as a means to distinguish between contributions from operators involving different fermion chiralities and Lorentz structures.

Learning physical parameters from dynamic scenes

Humans acquire their most basic physical concepts early in development, and continue to enrich and expand their intuitive physics throughout life as they are exposed to more and varied dynamical environments. We introduce a hierarchical Bayesian framework to explain how people can learn physical parameters at multiple levels. In contrast to previous Bayesian models of theory acquisition (Tenenbaum, Kemp, Griffiths, & Goodman, 2011), we work with more expressive probabilistic program representations suitable for learning the forces and properties that govern how objects interact in dynamic scenes unfolding over time. We compare our model to human learners on a challenging task of estimating multiple physical parameters in novel microworlds given short movies. This task requires people to reason simultaneously about multiple interacting physical laws and properties. People are generally able to learn in this setting and are consistent in their judgments. Yet they also make systematic errors indicative of the approximations people might make in solving this computationally demanding problem with limited computational resources. We propose two approximations that complement the top-down Bayesian approach. One approximation model relies on a more bottom-up feature-based inference scheme. The second approximation combines the strengths of the bottom-up and top-down approaches, by taking the feature-based inference as its point of departure for a search in physical-parameter space.

A new multi-line cusp magnetic field plasma device (MPD) with variable magnetic field.

A new multi-line cusp magnetic field plasma device consisting of electromagnets with core material has been constructed with a capability to experimentally control the relative volume fractions of magnetized to unmagnetized plasma volume as well as accurate control on the gradient length scales of mean density and temperature profiles. Argon plasma has been produced using a hot tungsten cathode over a wide range of pressures 5 × 10-5 -1 × 10-3 mbar, achieving plasma densities ranging from 109 to 1011 cm-3 and the electron temperature in the range 1-8 eV. The radial profiles of plasma parameters measured along the non-cusp region (in between two consecutive magnets) show a finite region with uniform and quiescent plasma, where the magnetic field is very low such that the ions are unmagnetized. Beyond that region, both plasma species are magnetized and the profiles show gradients both in temperature and density. The electrostatic fluctuation measured using a Langmuir probe radially along the non-cusp region shows less than 1% (δIisat/Iisat < 1%). The plasma thus produced will be used to study new and hitherto unexplored physics parameter space relevant to both laboratory multi-scale plasmas and astrophysical plasmas.

Identifying microturbulence regimes in a TCV discharge making use of physical constraints on particle and heat fluxes

Reducing the uncertainty on physical input parameters derived from experimental measurements is essential towards improving the reliability of gyrokinetic turbulence simulations. This can be achieved by introducing physical constraints. Amongst them, the zero particle flux condition is considered here. A first attempt is also made to match as well the experimental ion/electron heat flux ratio. This procedure is applied to the analysis of a particular Tokamak à Configuration Variable discharge. A detailed reconstruction of the zero particle flux hyper-surface in the multi-dimensional physical parameter space at fixed time of the discharge is presented, including the effect of carbon as the main impurity. Both collisionless and collisional regimes are considered. Hyper-surface points within the experimental error bars are found. The analysis is done performing gyrokinetic simulations with the local version of the GENE code, computing the fluxes with a Quasi-Linear (QL) model and validating the QL results with non-linear simulations in a subset of cases.

Exploring short-GRB afterglow parameter space for observations in coincidence with gravitational waves

Short duration Gamma Ray Bursts(SGRB) and their afterglows are among the most promising electro-magnetic (EM) counterparts of Neutron Star (NS) mergers. The afterglow emission is broadband, visible across the entire electro-magnetic window from $\gamma$-ray to radio frequencies. The flux evolution in these frequencies is sensitive to the multi-dimensional afterglow physical parameter space. Observations of gravitational wave (GW) from BNS mergers in spatial and temporal coincidence with SGRB and associated afterglows can provide valuable constraints on afterglow physics. We run simulations of GW-detected BNS events and assuming all of them are associated with a GRB jet which also produces an afterglow, investigate how detections or non-detections in X-ray, optical and radio frequencies can be influenced by the parameter space. We narrow-down the regions of afterglow parameter space for a uniform top-hat jet model which would result in different detection scenarios. We list inferences which can be drawn on the physics of GRB afterglows from multi-messenger astronomy with coincident GW-EM observations.

Interpreting hints for lepton flavor universality violation

We interpret the recent hints for lepton flavor universality violation in rare $B$ meson decays. Based on a model-independent effective Hamiltonian approach, we determine regions of new physics parameter space that give a good description of the experimental data on $R_K$ and $R_{K^*}$, which is in tension with Standard Model predictions. We suggest further measurements that can help narrowing down viable new physics explanations. We stress that the measured values of $R_K$ and $R_{K^*}$ are fully compatible with new physics explanations of other anomalies in rare $B$ meson decays based on the $b \to s \mu\mu$ transition. If the hints for lepton flavor universality violation are first signs of new physics, perturbative unitarity implies new phenomena below a scale of $\sim 100$ TeV.

Cryogenic Fab-on-a-Chip Sticks the Landing.

Using a microelectromechanical systems (MEMS)-based Fab-on-a-Chip, we quench-condense lead thin-films. Suppressing the formation of lead islands makes it possible to grow a homogeneous and continuous film as thin as 2 nm, without the use of an adhesion layer. Thermal cycling from 3 K to as low as 10 K reveals irreversible annealing of the thin-film characteristic of a metastable state. The transition to the stable state is smooth and is completed by cycling the temperature above ∼42 K, where a distinctive resistance minimum is observed. This resistive minimum is accompanied by an unexpected peak in the superconducting transition temperature. After further thermal cycling, the standard metallic/superconductive behavior is established. The MEMS-based approach yields a platform for systematic studies of quench-condensed thin-film materials, making an intriguing parameter space of mesoscopic physics experimentally accessible.

Constraining compressed versions of MUED and MSSM using soft tracks at the LHC

A compressed spectrum is an anticipated hideout for many beyond standard model scenarios. Such a spectrum naturally arises in the minimal universal extra dimension framework and also in supersymmetric scenarios. Low pT leptons and jets are characteristic features of such situations. Hence, a monojet with has been the conventional signal at the Large Hadron Collider (LHC). However, we stress that inclusion of pT -binned track observables from such soft objects provide very efficient discrimination of new physics signals against various SM backgrounds. We consider two benchmark points each for minimal universal extra dimension (MUED) and minimal supersymmetric standard model (MSSM) scenarios. We perform a detailed cut-based and multivariate analysis (MVA) to show that the new physics parameter space can be probed in the ongoing run of LHC at 13 TeV center-of-mass energy with an integrated luminosity ∼ 20-50 fb−1. When studied in conjunction with the dark matter relic density constraint assuming standard cosmology, we find that compressed MUED (with ΛR = 2) can be already excluded from the existing data. Also, MVA turns out to be a better technique than regular cut-based analysis since tracks provide uncorrelated observables which would extract more information from an event.

New physics effects in charm meson decays involving c rightarrow u l^+ l^- (l_i^{mp } l_j^{,pm ,}) transitions

We study the effect of the scalar leptoquark and Z^prime boson on the rare decays of the D mesons involving flavour changing transitions c rightarrow u l^+ l^- (l^{mp }_i l^{,pm ,}_j). We constrain the new physics parameter space using the branching ratio of the rare decay mode D^0 rightarrow mu ^+ mu ^- and the D^0 - {bar{D}}^0 oscillation data. We compute the branching ratios, forward–backward asymmetry parameters and flat terms in D^{+(0)} rightarrow pi ^{+(0)} mu ^+ mu ^- processes using the constrained parameters. The branching ratios of the lepton flavour violating D meson decays, such as D^0 rightarrow mu e, ~tau e and D^{+(0)} rightarrow pi ^{+(0)} mu ^- e^+ are also investigated.

Study of the rare decays

We investigate the effect of scalar leptoquarks and family non-universal bosons on the rare leptonic decays of mesons, mediated by the flavour-changing neutral-current transitions . They are sensitive to a variety of new physics operators as opposed to the leptonic modes and, hence, can provide an ideal testing ground to look for new physics beyond the Standard Model (SM). We work out the constraint on new physics parameter space using the measured branching ratios of processes and the mixing data. Using the constrained parameters we estimate the branching ratios of processes. We find that the branching ratios are reasonably enhanced from their corresponding SM values in the leptoquark model and are expected to be within the reach of Run II/III of Large Hadron Collider experiments.

The Relation between Fundamental Constants and Particle Physics Parameters

The observed constraints on the variability of the proton to electron mass ratio μ and the fine structure constant α are used to establish constraints on the variability of the Quantum Chromodynamic Scale and a combination of the Higgs Vacuum Expectation Value and the Yukawa couplings. Further model dependent assumptions provide constraints on the Higgs VEV and the Yukawa couplings separately. A primary conclusion is that limits on the variability of dimensionless fundamental constants such as μ and α provide important constraints on the parameter space of new physics and cosmologies.