String Mass Research Articles

Test particles and quasiperiodic oscillations around Kiselev black hole with cloud of strings* *Supported by the F-FA-2021-510 Grant of the Ministry of Innovative Development of Uzbekistan

In the present study, we investigate the dynamics of test particles around a Schwarzschild black hole surrounded by quintessence and immersed in a scalar string cloud field. We start our study by defining the possible values of the quintessence and cloud of string parameters corresponding to the existence of the black hole horizon for fixed values of the parameters of the equation of state for dark energy. We also study the effects of the effective potential on the circular motion, energy, and angular momentum of the test particles together with the innermost stable circular orbits (ISCOs). We investigate the fundamental frequencies in the particle oscillations along stable circular orbits. We relate the stability of the orbits to the Lyapunov exponent, and the chaotic behavior is studied graphically. Finally, we apply the fundamental frequencies to describe quasiperiodic oscillations (QPOs) and find that, in the presence of both fields, low-frequency twin-peak QPOs are not observed. In addition, we obtain the constraint values for the string cloud parameter and mass of the black hole candidates located in the center of the microquasars GRO J1655-40 and GRS 1915+105 as well as the Milky Way galaxy.

Growth characteristics and influence analysis of insulator strings in natural icing

Icing flashover of insulator strings has always been a serious factor threatening the safety and stability of the power grid. Researchers have simulated icing based on an artificial climate chamber, but it cannot fully simulate the growth process of insulator strings during the icing period in the natural environment. The icing growth characteristics of insulator strings in the natural environment are not clear. In this paper, three kinds of porcelain insulators were tested in the Xuefeng Mountain natural icing test base of Chongqing University. The results show that the freezing rain, alternating icing of freezing rain and freezing fog can cause the insulator stings to form glaze and mixed rime, and the icing degree on the windward side is more serious than leeward side. The higher the test environment's precipitation, humidity and wind speed, the faster the insulator strings’ icing speed. And there are also some influences of the ambient temperature on the icing morphology in this test. The icing thickness on the windward side of the insulator shed will gradually increase. The number of icicles of insulators is positively correlated with the diameter of insulator sheds. The icing mass of insulator strings is seriously affected by their shed structure.

Axion effective potentials induced by heavy sterile fermions

A model of (3 + 1)-dimensional leptogenesis, proposed previously by the authors, requires a CPT Violating (CPTV) background of the Kalb–Ramond (KR) axion field. The KR axion is a pseudoscalar, which is dual to the field strength of the spin-one field present in the massless gravitational multiplet in the theory of closed bosonic strings (compactified to four dimensions). Microscopic models for the emergence of such backgrounds are provided both by low-energy string-inspired gravitational theories with torsion (including (primordial) gravitational and axial gauge anomalies) and by Einstein–Cartan gravity, a closely related simpler model. In this work we examine the pseudoscalar quanta of the KR axion in this background using the methods of effective field theory. In our model for leptogenesis there is a single sterile right-handed neutrino (RHN) with mass m_N. At energies lower than m_N, an axion potential is derived by integrating out at one loop the sterile neutrino in the spirit of effective field theory. The stability of this axion potential is important for the viability of our model. The vacuum of this potential is generally metastable. The stability of the vacuum is determined by the ratio of the torsion-induced-axion coupling (which depends on the string mass scale) to m_N, which should be larger or equal to one, for the validity of our effective field theory. The vacuum is metastable only for axion couplings much larger than the sterile neutrino mass (large string mass scales, e.g. comparable to the four-dimensional Planck mass), with a lifetime much larger than the age of the observable Universe. By contrast, if axion couplings are comparable to the RHN mass the false vacuum is highly unstable, with a lifetime much smaller than the age of the observable Universe; in this case the CPTV leptogenesis scenario is not viable.

White feces syndrome in Penaeus vannamei is potentially an Enterocytozoon hepatopenaei (EHP) associated pathobiome origin of Vibrio spp

White feces syndrome (WFS) is a commercially important disease in Penaeus vannamei (whiteleg shrimp) farming. The aetiology beyond the white or golden white midgut with mediocre growth performance producing a floating mass of white fecal strings in WFS-affected shrimp farms remains uncharted. To give WFS a perception of pathobiome, healthy P. vannamei shrimps were subjected to an enteric microsporidian Enterocytozoon hepatopenaei (EHP) infection along with Vibrio harveyi and V. alginolyticus in different combinations. Immune responses in haemolymph (total haemocyte count (THC), prophenoloxidase activity (proPO), respiratory burst activity (RBA), superoxide dismutase activity (SOD) and catalase activity (CAT)), plasma biochemical changes (aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP)) and digestive enzymes activity (alpha-amylase (AMY), lipase (LIP) and protease (PRO)) were assessed in the challenged shrimps at 5, 10 and 15 days post-infection (dpi). The microbial interactions between the EHP and Vibrio spp. have led to the formation of WFS in the challenged shrimps. The histological sections of the hepatopancreas revealed the presence of EHP along with colonized bacterial masses, leading to the formation of aggregated transformed microvilli (ATM) structures and increased sloughing of lipid vacuoles into the tubule lumen. A significantly decreased THC and increased proPO levels, dysregulated antioxidant system, prominent hepatic damage, reduced energy metabolism and higher lipid production were the key records supporting that EHP-associated WFS in P. vannamei is due to the pathobiome.

Black strings from dark matter

In this paper, we obtain two static black string solutions by considering as sources axisymmetric dark matter (DM) distributions in 3+1 dimensions, in two different scenarios, namely, purely isotropic and radial orbits, which are regulated by two DM parameters. Both solutions tend asymptotically to the usual static and uncharged black string vacuum solution predicted by General Relativity (GR), and each of them presents an event horizon, which is larger than the one corresponding to the vacuum solution, as it is shown. We also show that the presence of DM turns these solutions singular at their symmetry axis. Then, we calculate the Hawking temperatures of these black string horizons and discuss some of their consequences. Unlike what occurs with the static black string vacuum solution, we find that there exists a linear density of mass (or tension) remnant associated with a vanishing Hawking temperature for the solutions under consideration. Thus, we analyze how the presence of DM affects the occurrence of the remnants. Further, we calculate other thermodynamic quantities, namely entropy, heat capacity, and free energy per unit length, showing that thermal phase transitions can occur in the presence of DM. We also analyze the weak (and null) energy conditions and conclude that DM does not behave like an exotic fluid. Finally, the corresponding stationary solutions are obtained, as well as their new tensions as functions of both the mass and angular momentum of the black strings.

Model Matematika Vibrasi Dawai Dikenai Massa yang Berjalan di Atasnya

This study discusses the formulation of a mathematical model of string vibration when subjected to mass. There are two variables resulting from the formulation of the model, namely the deflection of the string and the angle of the string . The deflection of the string and the angle of the string . are affected by the friction force, tension force, spring force, and gravity. Then the identification of the working potential and kinetic energy is carried out to obtain the Lagrange equation of the deflection and angle of the string. Based on the formulation steps that have been described, the mathematical model obtained is an ordinary differential equation of the order of one to the power of two. Furthermore, the model is calculated numerically by assigning values to the parameters involved. So it is known that with a string mass of 0.005 kg, 0.05 kg, 0.5 kg, a string mass of 0.075 kg, and an object radius of 0.07 m, it is known that the deflection of the string is greater if the object's mass is greater. While the angle of the string is in a state of equilibrium before being subjected to a mass and experiencing vibration after being subjected to a mass.

Non-commutativity and non-inertial effects on a scalar field in a cosmic string space-time: I. Klein–Gordon oscillator

We analyse the Klein–Gordon oscillator in a cosmic string space-time and study the effects stemming from the rotating frame and non-commutativity in momentum space. We show that the latter mimics a constant magnetic field, imparting physical interpretation to the setup. The field equation for the scalar field is solved via separations of variables, and we obtain quantization of energy and angular momentum. The space-time metric is non-degenerate as long as the particle is confined within a hard-wall, whose position depends on the rotation frame velocity and the string mass parameter. We investigate the energy quantization both for a finite hard-wall (numerical evaluation) and in the limit of an infinite hard-wall (analytical treatment). We stress the effect of non-commutativity upon the energy quantization in each case.

Asphaltene precipitation trend and controlling its deposition mechanism

The B oilfield is a large integrated oilfield in the Middle East. Asphaltene precipitates from crude oil and deposits on solid surfaces, affording considerable blockages of the formation, wellbore, and production equipment. To fully understand the asphaltene precipitation trend and deposition mechanism deeply, and solve the abovementioned problems in the B oilfield, fourier-transform infrared spectroscopy, proton nuclear magnetic resonance, and isothermal depressurization experiments (IDEs) have been conducted to predict the asphaltene precipitation trend of an oil sample. According to the experiments, the saturate, aromatic, resin, and asphaltene ratios were 5.6%, 37.4%, 33.1%, and 15.9%, respectively. The calculated colloidal instability index reached 0.88, indicating a risk of asphaltene precipitation. Based on IDEs, asphaltene precipitation was observed in the view cell window at 3196, 3545, and 3750 psi at different temperatures. Furthermore, the asphaltene deposition mechanism was studied on a string surface at the microscale based on molecular simulations and control measures were proposed. According to the simulations, the deposition process is found to be spontaneous. Asphaltene molecules were self-assembled and formed nanoaggregates in the form of a π–π conjugation. They were deposited parallelly on the string with a “face-to-face” pattern. When the simulation temperature reached 325 K, asphaltene deposition reached the maximum under the simulation conditions. Compared with omitting dispersants, the average distance between the asphaltene molecules and string mass center improved and the energy of the system had considerably lowered after adding dispersants, implying that dispersants can effectively weaken the asphaltene deposition process. This paper provides some suggestions for preventing and removing blockages of electric pumps caused by asphaltene deposition.

One-loop masses of Neumann-Dirichlet open strings and boundary-changing vertex operators

We derive the masses acquired at one loop by massless scalars in the Neumann-Dirichlet sector of open strings, when supersymmetry is spontaneously broken. It is done by computing two-point functions of “boundary-changing vertex operators” inserted on the boundaries of the annulus and Möbius strip. This requires the evaluation of correlators of “excited boundary-changing fields,” which are analogous to excited twist fields for closed strings. We work in the type IIB orientifold theory compactified on T2× T4/ℤ2, where mathcal{N} = 2 supersymmetry is broken to mathcal{N} = 0 by the Scherk-Schwarz mechanism implemented along T2. Even though the full expression of the squared masses is complicated, it reduces to a very simple form when the lowest scale of the background is the supersymmetry breaking scale M3/2. We use our results to analyze in this regime the stability at the quantum level of the moduli fields arising in the Neumann-Dirichlet sector. This completes the study of ref. [32], where the quantum masses of all other types of moduli arising in the open- or closed-string sectors are derived. Ultimately, we identify all brane configurations that produce backgrounds without tachyons at one loop and yield an effective potential exponentially suppressed, or strictly positive with runaway behavior of M3/2.

Light speed variation with brane/string-inspired space-time foam

Recently a series of studies on high energy gamma-ray burst (GRB) photons suggest a light speed variation with linear energy dependence at the Lorentz violation scale of 3.6×1017 GeV, with subluminal propagation of high energy photons in cosmological space. We propose stringy space–time foam as a possible interpretation for this light speed variation. In such a string-inspired scenario, bosonic photon open-string travels in vacuo at an infraluminal speed with an energy dependence suppressed by a single power of the string mass scale, due to the foamy structure of space–time at small scales, as described by D-brane objects in string theory. We present a derivation of this deformed propagation speed of the photon field in the infrared (IR) regime. We show that the light speed variation, revealed in the previous studies on GRBs time-delay data, can be well described within such a string approach towards space–time foam. We also derive the value of the effective quantum-gravity mass in this framework, and give a qualitative study on the theory-dependent coefficients. We comment that stringent constraints on Lorentz violation in the photon sector from complementary astrophysical observations can also be explained and understood in the space–time foam context.

Equivalence of solutions between the four-dimensional novel and regularized EGB theories in a cylindrically symmetric spacetime

Recently, a novel four-dimensional Einstein–Gauss–Bonnet (EGB) theory was presented to bypass the Lovelock’s theorem and to give nontrivial effects on the four-dimensional local gravity. The main mechanism is to introduce a redefinition alpha rightarrow alpha /(D-4) and to take the limit Drightarrow 4. However, this theory does not have standard four-dimensional field equations. Some regularization procedures are then proposed to address this problem (http://arxiv.org/abs/2003.11552, http://arxiv.org/abs/2003.12771, http://arxiv.org/abs/2004.08362, http://arxiv.org/abs/2004.09472, http://arxiv.org/abs/2004.10716). The resultant regularized four-dimensional EGB theory has the same on-shell action as the original theory. Thus it is expected that the novel four-dimensional EGB theory is equivalent to its regularized version. However, the equivalence of these two theories is symmetry-dependent. In this paper, we test the equivalence in a cylindrically symmetric spacetime. The well-defined field equations of the two theories are obtained, with which our follow-up analysis shows that they are equivalent in such spacetime. Cylindrical cosmic strings are then considered as specific examples of the metric. Three sets of solutions are obtained and the corresponding string mass densities are evaluated. The results reveal how the Gauss–Bonnet term in four dimensions contributes to the string geometry in the new theory.

Anomalous U(1) gauge bosons as light dark matter in string theory

Present experiments are sensitive to very weakly coupled extra gauge symmetries which motivates further investigation of their appearance in string theory compactifications and subsequent properties. We consider extensions of the standard model based on open strings ending on D-branes, with gauge bosons due to strings attached to stacks of D-branes and chiral matter due to strings stretching between intersecting D-branes. Assuming that the fundamental string mass scale saturates the current LHC limit and that the theory is weakly coupled, we show that (anomalous) U(1) gauge bosons which propagate into the bulk are compelling light dark matter candidates. We comment on the possible relevance of the U(1) gauge bosons, which are universal in intersecting D-brane models, to the observed 3σ excess in XENON1T.

Elements to improve theory of roller cutter bit with chisel teeth

The article deals with solving the problem of determination in the first approximation of the time of the interaction of tricone bit tooth with the rock and the maximum dynamic impact force. Considered the roller bit teeth are of types Sh and B. The shape of the bottom hole after the previous penetration the rock is adopted as having spherical mounds between paths. It is believed that deformations during the impact of the tooth occur only in the area of ​​the mounds, neglecting the masses of the rock material being deformed. The concept of the consolidated mass of the part of the rock, which is disintegrated and sections of the mass of the drill string with a roller bit is introduced. Separate consideration is given to determining the time and maximum impact force at the stages of sinking the rock and the raising of the tooth from it. In raising the plastic deformation of the material of the rock and its elastic return are taken into account. The determination of these parameters is carried out both without considering the moment of inertia of the roller bit, as well as taking into account this moment. It is shown that during the oblique impact of the tooth on the mound, taking into account the moment of inertia of the roller bit, it is necessary to know the coefficient of friction of the rocks over the tooth and the initial acceleration of the roller bit. In this case, the normal and the tangential component of the force of the specified impact of the tooth on the mound is considered separately. Were suggested analytical dependences for determination of the normal and tangent component of the shock interaction force module, as well as their maximum value.

Sturm–Liouville Problems Involving Distribution Weights and an Application to Optimal Problems

This paper is concerned with Sturm–Liouville problems (SLPs) with distribution weights and sets up the min–max principle and Lyapunov-type inequality for such problems. As an application, the paper solves the following optimization problems: If the first eigenvalue of a string vibration problem is known, what is the minimal total mass and by which distribution of weight is it attained; if both the first eigenvalue and the total mass are known, what is the corresponding results on the string mass? The vibration problem leads to a SLP with the spectral parameter in both the equation and the boundary conditions. Our main method is to incorporate this problem into the framework of classical SLPs with weights in an appropriate space by transforming it into the one with distribution weight, which provides a different idea for the investigation of the SLPs with spectral parameter in boundary condition.

Analytical investigation on the dynamics of the smooth and discontinuous oscillator

In this paper, the dynamics of a nonlinear smooth and discontinuous oscillator, modeled as a string–mass structure, is analyzed. This structure is convenient to be installed in vibration damping systems of high buildings for their protection in the case of earthquakes. The considered string–mass structure contains a translator movable mass connected with two strings. The motion of the mass is oscillatory and perpendicular to the string’s position. Usually, in strings preloading forces act. Due to geometric and physical properties of the system, the restitution force of the string is nonlinear. The model of the mass motion is a strong nonlinear second-order differential equation. The nonlinearity is of power type, and the order of nonlinearity is any positive real number. An exact solution of the truly nonlinear equation is introduced in the form of the Ateb function (inverse Beta function). Based on the exact solution, the approximate solving procedure of the nonlinear equation of motion is developed. The method is suitable for dynamic analyses of the system. The influence of the preloading force on the nonlinear vibrations of the string–mass system is considered. It is concluded that variation of the string force has influence on the velocity of the amplitude decrease in the system.

Open-string singlet interaction as pomeron in elastic pp, pbar{p} scattering

We consider contributions of the open-string singlet (OSS) interaction to the proton–proton scattering. Modelling baryon and meson as instanton and open string in the effective QCD string model, the typical pomeron is identified with a massive spin-2 closed string. According to the open-closed string duality, the massive spin-2 closed string is accompanied by the open-string singlet interaction with universal coupling. The flat space 4-point open-string singlet amplitudes and cross sections are computed in the Regge limit. Including both the open and closed string pomerons, we fit the differential cross-section with experimental data of the proton–proton and proton–antiproton scattering from the CDF, E-710, D0, LHC-ATLAS and LHC-TOTEM collaborations. The fitting results show the universality of the string mass scale (or string tension) and consistency of the string model between the open and closed string parameters in describing the pp and pbar{p} scattering in the Regge limit. The fitting of the string model to experimental data gives the string scale M_{S}simeq 1.7–1.8 GeV and the corresponding glueball pole mass m_{g}simeq 1.6–1.7 GeV. This lies within experimental values of the observed 2^{++}, I=0 “meson” masses.

Three spectra problem for Stieltjes string equation and Neumann conditions

Spectral problems are considered which appear in description of small transversal vibrations of Stieltjes strings. It is shown that the eigenvalues of the Neumann-Neumann problem, i.e. the problem with the Neumann conditions at both ends of the string interlace with the union of the spectra of the Neumann-Dirichlet problems, i.e. problems with the Neumann condition at one end and Dirichlet condition at the other end on two parts of the string. It is shown that the spectrum of Neumann-Neumann problem on the whole string, the spectrum of Neumann-Dirichlet problem on the left part of the string, all but one eigenvalues of the Neumann-Dirichlet problem on the right part of the string and total masses of the parts uniquely determine the masses and the intervals between them.

Tensegrity system dynamics with rigid bars and massive strings

This paper provides a single matrix-second-order nonlinear differential equation to simulate the dynamics of tensegrity systems with rigid bars and massive strings. The paper allows one to distribute the string mass into any specified number of point masses along the string while preserving the exact rigid bar dynamics. This formulation also allows modeling of skins and surfaces as a finite set of strings in the tensegrity dynamics. To reduce the complexity of the model, non-minimal coordinates (6 degrees of freedom for each bar instead of 5) were chosen. This is the key to give more accurate results in computer simulations since the mathematical structure of the model is simplified and exploited during numerical computations. A bar length correction algorithm is also provided for both class-1 and class- $k$ tensegrity systems to correct the erroneous change in bar length because of computational errors during numerical integration. We characterize the control variable as the force density in each string. This allows control laws to be developed independently of the material chosen for the structural elements. A nonlinear transformation back to the physical control variables involves the material properties.

Mathematical model of the system “manual vibration shock shaker – fruit branch”

Purpose. Development of mathematical model of oscillating system “manual vibration shock shaker – fruit branch” for the purpose of theoretical substantiation of the parameters of the shaker. Methods. The basic positions of mathematics, theoretical mechanics, mathematical modeling, program development and numerical calculations on the PC using methods of constructing mathematical models of functioning of agricultural machines are used. Results. The paper proposes a mathematical system model “manual vibration shock shaker – fruit branch” of six differential equations describing the motion of five separate masses (the mass of branch and four masses of individual shaker strings) and differential equations of the transverse and rotational motion of the system as whole. The mathematical system model determines the regularity of the motion of all masses, as well as the reactions of the viscals of the oscillatory system to the impact and after the impact that is generated in the shock mechanism. The proposed nonlinear, complex system of differential equations solves the numerical Runge-Kutta method of the fourth order of accuracy. On the basis of the calculated data the theoretical regularities of change of movement, speed and acceleration of a branch in the place of capture are received, which confirm that in the case of interaction of the cups of the shock mechanism there is blow that is accompanied by an increase in the acceleration of the branch, which is 4–5 times greater than the acceleration of the vibration mode of operation. Conclusions 1. The mathematical model of oscillating system “manual vibration shock shaker – fruit branch” is proposed in the form of system of six differential equations that allows to theoretically substantiate the basic modes of work of the manual shaker in the vibration shock mode to provide the agrotechnical necessary extraction completeness. 2. The received theoretical regularities of change of displacement, speed and acceleration of branch at the place of capture confirm the effectiveness of the vibration shock mode of the shaker. Due to the vibration-shock mode, the acceleration of the branch at the point of transmission of disturbing forces is 4–5 times higher than the acceleration of the vibrational operation mode. Keywords: manual shakes, vibration shocking process, oscillation oscillators, mathematical model, fruit branch, harvesting.

On the effects of damping on the dynamics of axially moving spatially periodic strings

The paper concerns the analysis of the effects of damping on the linear dynamics of an axially moving non-uniform structure, string with periodically varying mass and damping properties. The string, in particular models transmission chains for drive engines. An expression for the threshold velocity of the string axial motion is determined; if the string moves with a velocity higher than the threshold one, then waves travelling in it are unstable. For a uniform string, the threshold velocity equals to the transverse wave speed. It is shown that pure modulations of the string mass can increase the threshold velocity for waves with certain wavenumbers. By contrast, combined modulations of mass and damping properties lead to reduction of the threshold velocity as compared to the case of the uniform string. And the larger the amplitudes of the modulations, the more pronounced the reduction. This indicates that due to periodic spatial modulations of the string properties, the string dynamics can become unstable even if its axial velocity is considerably lower than the transverse wave speed. Thus, periodic distribution of damping and mass properties can considerably affect design of axially moving structures used in applications.