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When the source for the energy-momentum tensor is a bulk viscous fluid containing onedimensional cosmic strings, a spatially homogeneous and anisotropic Bianchi type-V cosmological model is considered in this paper in a scalar-tensor theory of gravitation proposed by Saez-Ballester, we derive a determinate solution utilizing the plausible physical conditions: (i) the scalar of spacetime expansion is proportional to the shear scalar; (ii) the baratropic equation of state for pressure and density; and (iii) the bulk viscous pressure is related to the energy density. The model's physical and kinematic features are also discussed. [ABSTRACT FROM AUTHOR]

Having highly tunable molecular topology is one of the most important characteristics of polymers that provides these materials with a wide range of interesting and unique properties. In particular, ring polymers exhibit a number of properties that are markedly distinct from their linear counterparts. Here, we compare and contrast the glass formation of unknotted, nonconcatenated ring and linear polymer melts having variable molecular mass based on molecular dynamics simulations of a coarse-grained model. After revealing an unusual property in the structure of small rings, we discuss the mass dependence of the structural relaxation time determined from the self-intermediate scattering function over a wide range of temperatures in both ring and linear polymers. As a general trend, we find that the characteristic temperatures (e.g., the glass transition temperature) and fragility of glass formation increase with increasing molecular mass in linear polymers, but the mass dependences of these properties are rather weak in the family of ring polymer models considered, in broad accord with experimental measurements. Importantly, we show that the glass formation of ring polymers can quantitatively be described by the string model, a model that is broadly consistent with the entropy theory of glass formation and that takes the mass of string-like clusters as a molecular realization of the abstract cooperatively rearranging regions. This opens the possibility of applying the configurational entropy-based theories to describe the glass formation of ring polymers, once the ring topology is taken into account. [ABSTRACT FROM AUTHOR]

Elastomeric rollers are important components in applications such as printing and roll-to-roll manufacturing. To gain insight into roller mechanics and provide a basis for further investigations into dynamic rolling problems where rolling instabilities may arise, we employ a specially-designed apparatus to obtain displacement and strain fields via digital image correlation (DIC) under applied loads. We test loading scenarios leading to impending slip of an elastomeric roller, mounted on a steel hub, and in contact with a glass (rigid) substrate. We first examine strain fields under normal loading and compare them with the closest analytical predictions. We then progress to analyzing the strain fields under combined normal and tangential loading. For each loading scenario, we discuss the displacement and strain fields of the roller sidewall and contact interface. We use a conceptual string model to explore how stick and slip zones develop within the contact area as well as how memory effects arise during cyclic loading. This memory effect is then verified experimentally using the DIC strain fields. Additionally, we demonstrate a means for identifying the stick zone area between the roller and substrate using the experimentally-obtained displacement fields. We believe the apparatus, and the ability to obtain experimental displacement and strain fields, will prove valuable in understanding roller mechanics and associated instabilities. • Digital image correlation for contact and sidewall analysis of an elastomeric roller. • Elastomeric roller deformation including the effects of friction in the contact area. • A conceptual model for visualizing memory effects and stick and slip development. • Measuring the decrease in stick zone area under increasing tangential load using DIC. • Memory effects are calculated during a loading cycle and result in residual strain. [ABSTRACT FROM AUTHOR]

In this paper, we have discussed string cosmological model within the framework of f (R , T) theory of gravity in homogeneous but anisotropic Bianchi Type-II space-time. We have considered cosmic string as a source of energy–momentum tensor. We get the solution of the corresponding field equations by assuming deceleration parameter q (t) = − 1 + β 2 β t + k , which is time-dependent (here, k and β are arbitrary constants). This particular form of scale factor enables us to explain the two scenarios, (i) By using recent constraints ( H 0 = 7 3. 8 , q 0 = − 0. 7 3) from supernovae type Ia union data (Cunha, Kinematic constraints to the transition redshift from supernovae type Ia union data, Phys. Rev. D79 (2009) 047301), we find the values of arbitrary constants β and k for which we have derived a cosmological model showing accelerating expansion universe (q < 0) only throughout the evolution and (ii) By using the recent constraints ( H 0 = 7 3. 8 , and q 0 = − 0. 5 4) from SNIa data in combination with BAO and CMB observations (Giostri et al. From cosmic deceleration to acceleration: new constraints from SN Ia and BAO/CMB, J. Cosmol. Astrophys.3 (2012) 27), we find the values of arbitrary constants for which we have derived a cosmological model with phase transition from early decelerating (q > 0) to the present accelerating (q < 0) universe. Also, for the model, we have evaluated and discussed the various physical and kinematic parameters. We have also shown the variation of these cosmological parameters graphically for specific values of the constants. The stability and physical viability are also discussed for the derived models using some recently developed diagnostic tools. [ABSTRACT FROM AUTHOR]

In this paper we are interested to investigate spatially homogeneous and anisotropic Bianchi type-V cosmological model in the presence of cosmic string source coupled with an attractive massive scalar meson field. We have obtained a deterministic cosmological model using some relevant physical and mathematical conditions. Also we have determined cosmological parameters like average Hubble parameter, shear scalar, scalar expansion, string tension density and the energy density of the string. We have also obtained the massive scalar field in the model. A detailed discussion of the above physical quantities is, also, presented [ABSTRACT FROM AUTHOR]

We count the number of bound states of BPS black holes on local Calabi-Yau three-folds involving a Riemann surface of genus g. We show that the corresponding gauge theory on the brane reduces to a q-deformed Yang-Mills theory on the Riemann surface. Following the recent connection between the black hole entropy and the topological string partition function, we find that for a large black hole charge N, up to corrections of O(e^-N), Z_BH is given as a sum of a square of chiral blocks, each of which corresponds to a specific D-brane amplitude. The leading chiral block, the vacuum block, corresponds to the closed topological string amplitudes. The sub-leading chiral blocks involve topological string amplitudes with D-brane insertions at 2g-2 points on the Riemann surface analogous to the Omega points in the large N 2d Yang-Mills theory. The finite N amplitude provides a non-perturbative definition of topological strings in these backgrounds. This also leads to a novel non-perturbative formulation of c=1 non-critical string at the self-dual radius.

We investigate the geometry of four dimensional black hole solutions in the presence of stringy higher curvature corrections to the low energy effective action. For certain supersymmetric two charge black holes these corrections drastically alter the causal structure of the solution, converting seemingly pathological null singularities into timelike singularities hidden behind a finite area horizon. We establish, analytically and numerically, that the string-corrected two-charge black hole metric has the same Penrose diagram as the extremal four-charge black hole. The higher derivative terms lead to another dramatic effect -- the gravitational force exerted by a black hole on an inertial observer is no longer purely attractive! The magnitude of this effect is related to the size of the compactification manifold.

After reviewing the cosmological constant problem -- why is Lambda not huge? -- I outline the two basic approaches that had emerged by the late 1980s, and note that each made a clear prediction. Precision cosmological experiments now indicate that the cosmological constant is nonzero. This result strongly favors the environmental approach, in which vacuum energy can vary discretely among widely separated regions in the universe. The need to explain this variation from first principles constitutes an observational constraint on fundamental theory. I review arguments that string theory satisfies this constraint, as it contains a dense discretuum of metastable vacua. The enormous landscape of vacua calls for novel, statistical methods of deriving predictions, and it prompts us to reexamine our description of spacetime on the largest scales. I discuss the effects of cosmological dynamics, and I speculate that weighting vacua by their entropy production may allow for prior-free predictions that do not resort to explicitly anthropic arguments.

We devise minimalistic gauged U(1)_X Froggatt-Nielsen models which at low-energy give rise to the recently suggested discrete gauge Z_6 symmetry, proton hexality, thus stabilizing the proton. Assuming three generations of right-handed neutrinos, with the proper choice of X-charges, we obtain viable neutrino masses. Furthermore, we find scenarios such that no X-charged hidden sector superfields are needed, which from a bottom-up perspective allows the calculation of g_string, g_X and G_SM's Kac-Moody levels. The only mass scale apart from M_grav is m_soft.

We construct a gauge-mediation model with a D-term supersymmetry (SUSY) breaking. R-symmetry breaking necessary for generating the SUSY standard-model gaugino masses is given by gaugino condensation of a strongly coupled gauge theory in the hidden sector. The energy scale of the strong dynamics of the hidden sector gauge theory should be around the messenger mass scale M, or otherwise perturbative calculations would be reliable and would lead to negative soft mass squared for squarks and sleptons. Thus, all the mass scales are controlled by a virtually single parameter, \sqrt{D}/M. This model covers a very wide range of gravitino mass, m_{3/2} \simeq 1 eV--100 TeV. Possible embeddings of the model in string theory are also discussed.

The energy density of the vacuum, Lambda, is at least 60 orders of magnitude smaller than several known contributions to it. Approaches to this problem are tightly constrained by data ranging from elementary observations to precision experiments. Absent overwhelming evidence to the contrary, dark energy can only be interpreted as vacuum energy, so the venerable assumption that Lambda=0 conflicts with observation. The possibility remains that Lambda is fundamentally variable, though constant over large spacetime regions. This can explain the observed value, but only in a theory satisfying a number of restrictive kinematic and dynamical conditions. String theory offers a concrete realization through its landscape of metastable vacua.

Given the β functions of the closed string sigma model up to one loop in α ′ , the effective action implements the condition β = 0 to preserve conformal symmetry at quantum level. One of the more powerful and striking results of string theory is that this effective action contains Einstein gravity as an emergent dynamics in space–time. We show from the β functions and its relation with the equations of motion of the effective action that the differential identities are the Noether identities associated with the effective action and its gauge symmetries. From here, we reconstruct the gauge and space–time symmetries of the effective action. In turn, we can show that the differential identities are the contracted Bianchi identities of the field strength H and Riemann tensor R. Next, we apply the same ideas to DFT. Taking as starting point that the generalized β functions in DFT are proportional to the equations of motion, we construct the generalized differential identities in DFT. Relating the Noether identities with the contracted Bianchi identities of DFT, we were able to reconstruct the generalized gauge and space–time symmetries. Finally, we recover the original β functions, effective action, differential identities, and symmetries when we turn off the x ̃ space–time coordinates from DFT. [ABSTRACT FROM AUTHOR]

We discuss dynamical and covariant introduction of isospin quantum number into a composite string model. [ABSTRACT FROM AUTHOR]

This paper describes a simplified tuning system for the physical modelling of theGayageum, a Korean traditional plucked string instrument. In a previous work, anAnjokmodel was proposed as part of the string model to control pitch. However, this model has a maximum error of 7.75 Hz for the low fundamental frequencies. In order to ameliorate this situation, this paper modifies the assumption of the previous model and proposes a method to design a simplified tuning system. The optimal parameter of the system is determined based on the minimax algorithm and the error is 1.14 Hz on average. Furthermore, the maximum error decreases to about one third that of the previous method. [ABSTRACT FROM PUBLISHER]

We discuss spectrum of lightest mesons in NN̅ channel in the framework of composite superconformal string model and give estimation for η-mesons masses. [ABSTRACT FROM AUTHOR]

Spatially homogeneous and anisotropic Kantowski-Sachs space-time is considered in the scale covariant theory of gravitation proposed by Canuto et al. (Phys. Rev. Lett. 39:429, ) in the presence of bulk viscous fluid containing one dimensional cosmic strings. A determinate solution of the field equations of this theory is presented using the special law of variation proposed by Bermann (Nuovo Cimento B74:183, ). We have also used the proportionality of shear scalar to the scalar expansion of the space time. The solution obtained represents a bulk viscous string cosmological model in this theory. Some physical and kinematical properties of the model are also discussed. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated spatially homogeneous and anisotropic Kantowski-Sachs cosmological model in Lyra (Math. Z. 54:52, ) manifold in the presence of bulk viscous fluid containing one dimensional Cosmic strings. To obtain a determinate solution of the field equations, we have used some plausible physical conditions. The solution obtained represents a bulk viscous string cosmological model in Lyra geometry. Some physical and geometrical properties of the model are also discussed. [ABSTRACT FROM AUTHOR]

The WZNW and string models are considered in terms of the initial and invariant chiral currents assuming that the internal and external torsions coincide (anticoincide) and they are the structure constants of the SU(n), SO(n), SP(n) Lie algebras. These models are the auxiliary problems in order to construct integrable equations of hydrodynamic type. It was shown that the WZNW and string models in terms of invariant chiral currents are integrable for the constant torsion associated with the structure constants of the SU(2), SO(3), SP(2) and SU(3) algebras only. The equation of motion for the density of the first Casimir operator was obtained in the form of the inviscid Burgers equation. The solution of this equation is presented through the Lambert function. Also, a new equation of motion for the initial chiral current was found. The integrable infinite hydrodynamic chains obtained from the WZNW and string models are given in terms of invariant chiral currents with the SU(2), SO(3), SP(2) and with SU(∞), SO(∞), SP(∞) constant torsions. Also, the equations of motion for the density of any Casimir operator and new infinite-dimensional equations of hydrodynamic type for the initial chiral currents through the symmetric structure constant of SU(∞), SO(∞), SP(∞) algebras are obtained. [ABSTRACT FROM AUTHOR]

In this paper, a spatially homogeneous and anisotropic Bianchi type-V cosmological model is considered in a scalar-tensor theory of gravitation proposed by Saez and Ballester (in Phys. Lett. A 113:467, 1986 ) when the source for energy momentum tensor is a bulk viscous fluid containing one dimensional cosmic strings. The field equations being highly non-linear, we obtain a determinate solution using the plausible physical conditions (i) the scalar of expansion of the space-time is proportional to shear scalar (ii) the baratropic equation of state for pressure and density and (iii) the bulk viscous pressure is proportional to the energy density. It is interesting to observe that cosmic strings do not survive in this model. Some physical and kinematical properties of the model are also discussed. [ABSTRACT FROM AUTHOR]

A spatially homogeneous and anisotropic Bianchi type-III space-time is considered in the framework of a scalar-tensor theory of gravitation proposed by Brans and Dicke (Phys. Rev. 124:925, 1961 ) in the presence of bulk viscous fluid containing one dimensional cosmic strings. We have found a determinate solution of the field equations using the plausible physical conditions (i) a barotropic equation state for the pressure and density, (ii) special law of variation for Hubble’s parameter proposed by Berman (Nuovo Cimento B74:182, 1983 ), (iii) shear scalar is proportional to scalar expansion and (iv) the trace of the energy tensor of the fluid vanishes. We have also assumed that bulk viscous pressure is proportional to energy density. Some physical and kinematical properties of the model are, also, discussed. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a spatially homogeneous and anisotropic Bianchi type-V cosmological model in a scalar-tensor theory of gravitation proposed by Harko et al. (Phys. Rev. D 84:024020, ) when the source for energy momentum tensor is a bulk viscous fluid containing one dimensional cosmic strings. To obtain a determinate solution, a special law of variation proposed by Berman (Nuovo Cimento B 74:182, ) is used. We have also used the barotropic equation of state for the pressure and density and bulk viscous pressure is assumed to be proportional to energy density. It is interesting to note that the strings in this model do not survive. Also the model does not remain anisotropic throughout the evolution of the universe. Some physical and kinematical properties of the model are also discussed. [ABSTRACT FROM AUTHOR]

Charmed baryon spectroscopy has been studied under a string model. In this model, charmed baryons are composed of a diquark and a charm quark which are connected by a constant tension. In this diquark picture, the quantum numbers JP of confirmed baryons have been well assigned. Energies of the first and second orbital excitations have been predicted and compared with the experimental data. Meanwhile, diquark masses have been extracted in the background of charm quark which satisfy a splitting relation based on spin–spin interaction. [ABSTRACT FROM AUTHOR]

We study the SL(2,R) WZWN string model describing bosonic string theory in AdS3 spacetime as a deformed oscillator together with its mass spectrum and the string modified SL(2,R) uncertainty relation. The SL(2,R) string oscillator is far more quantum (with higher quantum uncertainty) and more excited than the non-deformed one. This is accompassed by the highly excited string mass spectrum which is drastically changed with respect to the low excited one. The highly excited quantum string regime and the low excited semiclassical regime of the SL(2,R) string model are described and shown to be the quantum-classical dual of each other in the precise sense of the usual classical-quantum duality. This classical-quantum realization is not assumed nor conjectured. The quantum regime (high curvature) displays a modified Heisenberg's uncertainty relation, while the classical (low curvature) regime has the usual quantum mechanics uncertainty principle. [ABSTRACT FROM AUTHOR]

By adopting the co-moving coordinate system, an exact axially symmetric cosmological model with string dust cloud source is obtained in the framework of Brans-Dicke [Phys. Rev. 124, 925, (1961) Scalar – tensor theory of gravitation. Some physical and kinematical properties of the model are also discussed. [ABSTRACT FROM AUTHOR]

We review the gauge symmetry breaking mechanism due to orbifold projections in orbifold model building. We explicitly show the existence of a scale of breaking if such a symmetry breaking is due to freely-acting orbifold operators only, i.e. in case the breaking is realized nonlocally in the internal space. We show that such a scale is related to the compactification moduli only, and that there are no extra continuous parameters, at least in semirealistic models with $\mathcal{N}=1$ SUSY in four dimensions. In this sense, the mechanism is peculiarly different from the standard Higgs (or Hosotani) symmetry breaking mechanism. We show that the mechanism also differs from that present in standard orbifold models where, even in the presence of discrete Wilson lines, a scale of breaking is generically missing, since the breaking is localized in specific points in the internal space. We review a set of background geometries where the described nonlocal breaking is realized, both in the case of two and six extra dimensions. In the latter case, relevant in string model building, we consider both heterotic and open string compactifications. [ABSTRACT FROM AUTHOR]

The lateral response of vertically translating media with variable length and tension, subjected to general initial conditions and external excitation, are determined. The translating media are modelled as a taut string and tensioned beams with pinned and fixed boundaries. In each model a rigid body is attached to the lower end of the medium and has a prescribed displacement along the horizontal direction. The rate of change in the energy of the translating medium is analysed from the control volume and system viewpoints. The models are used to predict the forced response of a moving cable in a high-speed elevator. Three spatial discretization schemes are used to calculate the response and shown to yield the same results. The convergence of the solution for each model is investigated. The approximate solution for the string model with constant tension is compared with its exact solution from the wave method. [ABSTRACT FROM AUTHOR]

Entropy production by a dilaton decay is studied in the model where the dilaton acquires potential via gaugino condensation in the hidden gauge group. Its effect on the Affleck-Dine baryogenesis is investigated. It is shown that the baryon asymmetry produced by this mechanism with the higher-dimensional terms is diluted by the dilaton decay and can be regulated to the observed value. [ABSTRACT FROM AUTHOR]

Two direction guided annealing modi¢cations to the traditional simulated annealing algorithm for solving the Vehicle Routing Problems (VRP) are proposed in this paper. The aim is to avoid searching solution space where the optimal solutions are not likely to be in. The string model of the VRP is adopted in these algorithms. The first approach is called the probability-based guided annealing algorithm, in which guide coefficients are formulated as probabilities for breaking and establishing connections between nodes. Based on these coefficients, a formulation is proposed to decide whether a stochastically generated exchange request between nodes is accepted for further computation or not. A detailed description of the algorithm is given. The algorithm is then implemented to solve a 100 shops capacitated VRP(CVRP). Three commonly used exchange rules are used for testing the performance of the algorithm: 1 to 1, random-insert, and 2-opt. Both computation time and distribution of the optimization cost function are measured and compared among the three exchange rules. Comparisons are also made with the traditional simulated annealing algorithm to contrast the superior efficiency of the new algorithm. Another guided annealing algorithm introduced in the paper is the pair-wise competitive annealing algorithm. The top N distances measured from each customer to surrounding nodes are chosen for the purpose of generating new solution states by the 2-opt exchange rule. The effective search space is decreased by only examining a smaller array containing the distance relationships for potentially shorter routes, when compared to straight-forward implementation of the traditional simulated annealing. A detailed listing of the algorithm is given, which is then implemented to solve the CVRP computationally. Similar experimental setups to the probability-based guided annealing algorithm are used. The given results show that the algorithm yields better solutions than that of the traditional simulated annealing, and with a much reduced computation time. Considerations and justifications on choosing the parameter N are also given. [ABSTRACT FROM AUTHOR]

String representation of the [U(1)]N−1 gauge-invariant dual Abelian–Higgs-type theory, which is relevant to the SU(N)-QCD with the Θ-term and provides confinement of quarks, is derived. The N-dependence of the Higgs vacuum expectation value is found, at which the tension of the string joining quarks becomes N-independent, similarly to the real QCD. Contrary to that, the inverse coupling constant of the rigidity term of this string always behaves approximately as 1/N. A long-range Aharonov–Bohm-type interaction of a dyon (i.e., a quark which acquired a magnetic charge due to the Θ-term) with a closed electric string becomes nontrivial at Θ≠Nπ×integer. On the contrary, at these critical values of Θ, the scattering of dyons over strings is absent. [Copyright &y& Elsevier]

Boson stars built from a very light Kalb–Ramond axion, the dilaton or other moduli fields of effective string models could provide a considerable fraction of the non-baryonic part of dark matter. Gravitational microlensing of ∼0.5 M⊙ MACHOs within the halo of galaxies may indirectly "weighing" the mass of the constituent scalar particle, resulting in ∼10−10 eV/c2. [ABSTRACT FROM AUTHOR]

• The string model and kinetic equations were proposed. • Axial and lateral displacement at any point and any time can be obtained. • Vibration of different tensional amount was investigated. • The sieving behaviors of particles were investigated. Flip-flow screen is an effective solution for screening high-viscosity and fine-grained materials, because of the large vibration intensity of the screen panel. Therefore, investigating the dynamic characteristics of the screen panel is the key to improving the flip-flow screen. In this paper, a new dynamic model is proposed to do dynamic analysis of screen panel. The vibration of the screen panel is simplified into a string vibration model, and the energy equation is established. Then, the Hamilton principle and the Galerkin method are employed to transform the energy equations into ordinary differential equations, with the numerical solutions obtained using MATLAB. The vibration model is established by ABAQUS to obtain the displacement data of each point on the screen panel. To verify the correctness and accuracy of the theory, the simulation results are compared with the theoretical calculation results, and the dynamic characteristics of the vibration of the screen panel are analyzed. Besides, displacement and velocity equations of particle on the screen panel based on the screen panel vibration theory are proposed. A new FEM-DEM (Finite Element Method-Discrete Element Method) coupling simulation model is established in ABAQUS, which is used to investigate the trajectory of one particle and the effect of screen panel's acceleration on particles' movement and screening percentage. [ABSTRACT FROM AUTHOR]