String Solutions Research Articles

Rotating black strings in de Rham-Gabadadze-Tolley massive gravity

One of the solutions of Einstein field equation with cylindrical symmetry is known as black string solution. In this work, the rotating black string solution in dRGT massive gravity is obtained and then called rotating-dRGT black string solution. This solution is a kind of generalized version of rotating AdS/dS black sting solution containing an additional two more terms characterizing the structure of graviton mass. The horizon structures of the black string are explored. The thermodynamical properties of the black string are investigated. We found that it is possible to obtain the Hawking-Page phase transition depending on the additional structure of the graviton mass, while it is not possible for rotating-AdS/dS black string. By analyzing the free energy, we also found that the stable rotating black string is bigger than the non-rotating one.

Stable three generation standard-like model from a tachyonic ten dimensional heterotic-string vacuum

Recently it was proposed that the ten dimensional tachyonic superstring vacua may serve as good starting points for the construction of viable phenomenological models. Such phenomenologically viable models enlarge the space of possible string solutions, and may offer novel insight into some of the outstanding problems in string phenomenology. In this paper we present a three generation standard-like model that may be regarded as a compactification of a ten dimensional tachyonic vacuum. We discuss the features of the model as compared to a similar model that may be regarded as compactification of the ten dimensional SO(16)times SO(16) heterotic-string. We further argue that in the four dimensional model all the geometrical moduli are fixed perturbatively, whereas the dilaton may be fixed by hidden sector non-perturbative effects.

Circular Wilson loops in defect mathcal{N} = 4 SYM: phase transitions, double-scaling limits and OPE expansions

We consider circular Wilson loops in a defect version of mathcal{N} = 4 super-Yang- Mills theory which is dual to the D3-D5 brane system with k units of flux. When the loops are parallel to the defect, we can construct both BPS and non-BPS operators, depending on the orientation of the scalar couplings in the R-symmetry directions. At strong ’t Hooft coupling we observe, in the non supersymmetric case, a Gross-Ooguri-like phase transition in the dual gravitational theory: the familiar disk solution dominates, as expected, when the operator is far from the defect while a cylindrical string worldsheet, connecting the boundary loop with the probe D5-brane, is favourite below a certain distance (or equivalently for large radii of the circles). In the BPS case, instead, the cylindrical solution does not exist for any choice of the physical parameters, suggesting that the exchange of light supergravity modes always saturate the expectation value at strong coupling. We study the double-scaling limit for large k and large ’t Hooft coupling, finding full consistency in the non-BPS case between the string solution and the one-loop perturbative result. Finally we discuss, in the BPS case, the failure of the double-scaling limit and the OPE expansion of the Wilson loop, finding consistency with the known results for the one-point functions of scalar composite operators.

New type of string solutions with long range forces

We explore the formation and the evolution of the string network in the Abelian Higgs model with two complex scalar fields. A special feature of the model is that it possesses a global U(1) symmetry in addition to the U(1) gauge symmetry. Both symmetries are spontaneously broken by the vacuum expectation values of the two complex scalar fields. As we will show the dynamics of the string network is quite rich compared with that in the ordinary Abelian Higgs model with a single complex scalar field. In particular, we find a new type of string solutions in addition to the conventional Abrikosov-Nielsen-Olesen (local) string solution. We call this the uncompensated string. An isolated uncompensated string has a logarithmic divergent string tension as in the case of the global strings, although it is accompanied by a non-trivial gauge field configuration. We also perform classical lattice simulations in the 2 + 1 dimensional spacetime, which confirms the formation of the uncompensated strings at the phase transition. We also find that most of the uncompensated strings evolve into the local strings at later time when the gauge charge of the scalar field with a smaller vacuum expectation value is larger than that of the scalar field with a larger vacuum expectation value.

Heating up holography for single-trace Joverline{T} deformations

We study thermodynamic aspects of a tractable toy model of holography for extremal Kerr black holes proposed in [1]. On the gravity side, the theory can be described by the worldsheet action of string theory on a warped AdS3 background supported by NS-NS flux. Once we turn on temperature, the deformed background is described by a black string solution of type IIB supergravity that features a locally warped AdS3 factor. The dual field theory is conjectured to be a single-trace version of a Joverline{T} -deformed CFT at finite temperature. As evidence for the correspondence we show that the spectrum of strings winding on the deformed background agrees with the spectrum of Joverline{T} -deformed CFTs. Furthermore, we show that the gravitational charges of the black string match the averaged charges of a thermal ensemble in the dual field theory. Finally, we reproduce the Bekenstein-Hawking entropy of the black string from the microscopic density of states of Joverline{T} -deformed CFTs.

Spin chains and classical strings in two parameters q-deformed AdS3 × S3

In this paper, we study the spin chain and string excitation in the two-parameters q-deformed AdS3 × S3 proposed by Hoare [6]. We obtain the deformed spin chain model at the fast spin limit for choices of deformed parameters. General ansatz for giant magnons are studied in great detail and complicated dispersion relation is treated perturbatively. We also study several types of hanging string solutions and their charges and spins are analyzed numerically. At last, we explore its pp-wave limit and find its solution only depends on the difference of deformed parameters.

Rotating black string in Born–Infeld gravity’s rainbow

Compact objects endowed with rotation and charge are interesting both from physical and mathematical points of view. Motivated by the recent interesting consequences of gravity’s rainbow, in this paper we introduce energy-dependent asymptotically anti-de Sitter black string solutions of Einstein–Born–Infeld gravity. We report the geometric properties of the solutions and generalize them to rotating black string solutions through an improper local transformation. We calculate the conserved and thermodynamic quantities of rotating black strings and examine the validity of the first law of thermodynamics. In addition, the effects of both rainbow functions and nonlinear electrodynamics on the thermodynamic behavior of the solutions will be studied. Finally, we investigate the thermal stability of the solutions using different methods.

Rotating strings in six-dimensional higher-derivative supergravity

We construct the first rotating string solution in 6-dimensional Einstein-Gauss-Bonnet supergravity, carrying both electric and magnetic charges. By embedding the known rotating string solution of the 2-derivative theory into 6-dimensional off-shell supergravity, the Killing spinors associated with the underlying supersymmetry can be made off-shell and are universal to all off-shell supergravity models based on the same field content. The near-horizon geometry is S^3 fibred over the extremal BTZ black hole, locally isomorphic to AdS_3*S^3. We compute the higher-derivative corrections to the Brown-Henneaux central charges in a particular R+R^2 model resulting from K3 compactification of type IIA string theory.

De Sitter, α′-corrections & duality invariant cosmology

Demanding O(d,d)-duality covariance, Hohm and Zwiebach have written down the action for the most general cosmology involving the metric, b-field and dilaton, to all orders in α′ in the string frame. Remarkably, for an FRW metric-dilaton ansatz the equations of motion turn out to be quite simple, except for the presence of an unknown function of a single variable. If this unknown function satisfies some simple properties, it allows de Sitter solutions in the string frame. In this note, we write down the Einstein frame analogues of these equations, and make some observations that make the system tractable. Perhaps surprisingly, we find that a necessary condition for de Sitter solutions to exist is that the unknown function must satisfy a certain second order non-linear ODE. The solutions of the ODE do not have a simple power series expansion compatible with the leading supergravity expectation. We discuss possible interpretations of this fact. After emphasizing that all (potential) string and Einstein frame de Sitter solutions have a running dilaton, we write down the most general cosmologies with a constant dilaton in string/Einstein frame: these have power law scale factors.

On pulsating strings in Schrodinger backgrounds

According to AdS/CFT duality semi-classical strings in the Schrodinger space­ time is conjectured to be a holographic dual to dipole CFT. In this paper we consider pulsating strings in five-dimensional Schrodinger space times five-sphere. We have found classical string solutions pulsating entirely in the Schrodinger part of the background. We quantize the theory semi-classically and obtain the wave function of the problem. We have found the corrections to the energy, which by duality are supposed to give anomalous dimensions of certain operators in the dipole CFT.

Salient features of dressed elliptic string solutions on mathbb {R}times hbox {S}^2

We study several physical aspects of the dressed elliptic strings propagating on mathbb {R} times mathrm {S}^2 and of their counterparts in the Pohlmeyer reduced theory, i.e. the sine-Gordon equation. The solutions are divided into two wide classes; kinks which propagate on top of elliptic backgrounds and non-localised periodic disturbances of the latter. The former class of solutions obey a specific equation of state that is in principle experimentally verifiable in systems which realize the sine-Gordon equation. Among both of these classes, there appears to be a particular class of interest the closed dressed strings. They in turn form four distinct subclasses of solutions. One of those realizes instabilities of the seed elliptic solutions. The existence of such solutions depends on whether a superluminal kink with a specific velocity can propagate on the corresponding elliptic sine-Gordon solution. Unlike the elliptic strings, the dressed ones exhibit interactions among their spikes. These interactions preserve an appropriately defined turning number, which can be associated to the topological charge of the sine-Gordon counterpart. Finally, the dispersion relations of the dressed strings are studied. A qualitative difference between the two wide classes of dressed strings is discovered.

Stability analysis of classical string solutions and the dressing method

The dressing method is a technique to construct new solutions in non-linear sigma models under the provision of a seed solution. This is analogous to the use of autoBäcklund transformations for systems of the sine-Gordon type. In a recent work, this method was applied to the sigma model that describes string propagation on ℝ × S2, using as seeds the elliptic string solutions. Some of the new solutions that emerge reveal instabilities of their elliptic precursors [1]. The focus of the present work is the fruitful use of the dressing method in the study of the stability of closed string solutions. It establishes an equivalence between the dressing method and the conventional linear stability analysis. More importantly, this equivalence holds true in the presence of appropriate periodicity conditions that closed strings must obey. Our investigations point to the direction of the dressing method being a general tool for the study of the stability of classical string configurations in the diverse class of symmetric spacetimes.

Three dimensional black strings: instabilities and asymptotic charges

Three-dimensional Einstein gravity coupled to zero, one and two forms is solved in terms of a polyhomogeneous asymptotic expansion, generalising stationary black string solutions. From first order terms we obtain, in closed form, a new solution evolving from the stationary black string structure to a geometry developing a singularity in the future. This new solution itself may be extended to more general ones. Taking into account subleading terms of the asymptotic expansion, both singularities in the past and the future occur. This demonstrates the unstable character of the stationary black string: tiny perturbations generated by terms breaking the rotational invariance of the stationary black string configurations lead to cosmological-like singularities. The symmetry algebra of the conserved charges also is determined: it is a finite dimensional one. In the general case the surface charge associated to energy is not integrable. However we identify a sub-class of solutions, admitting asymptotic symplectic symmetries and as a consequence conserved charges that appear to be integrable.

Charged dilaton solutions and black hole formation in three dimensions

In this paper, we present the charged dilaton solutions and black hole formation in three dimensions. Firstly we revisit the famous Chan–Mann charged dilaton black hole, describing one parameter family of static charged black hole solution in three dimensional Einstein–Maxwell–Dilaton gravity. This solution with a special parameter choice b=4a can lead to the three dimensional string solution. Then we give another class of charged dilaton black hole solution with bne 4a. We discuss their geometrical properties, the horizon structure and the causal structure. The time-dependent solution is also presented, which can characterize the three dimensional charged black hole formation in Einstein–Dilaton gravity. Especially, there is no exact time-dependent solution describing the gravitational collapse to the Chan–Mann charged dilaton black hole. Finally, we discuss the gravitational collapse of a dilaton field in the context of the Cosmic Censorship Conjecture.

Cohomogeneity-one-string integrability of spacetimes

A classical string whose world sheet shares a one-dimensional symmetry with the spacetime is called cohomogeneity-one (C1). We propose C1-string integrability, i.e. integrability of all C1 strings in the spacetime, as a class of hidden symmetry of a spacetime. The C1 string may probe symmetry which is not probed by a particle. We present a simple, systematic procedure for finding constants of motion of a C1 string and examining C1 string integrability of a spacetime. We apply the framework to some physically important spacetimes such as , , and . C1 strings and C1-string integrability may be useful for a prior examination of general string integrability of a highly symmetric spacetime since, among the examples above, all C1 string integrable spacetimes are string-integrable, and the previously obtained chaotic string solutions in those or other spacetimes are of class C1.

Supersymmetric dyonic strings in 6-dimensions from 3-dimensions

It was shown in arXiv:1410.7168 that compactifying D = 6, mathcal{N}=left(1,0right) ungauged supergravity coupled to a single tensor multiplet on S3 one gets a particular D = 3, mathcal{N}=4 gauged supergravity which is a consistent reduction. We construct two supersymmetric black string solutions in this 3-dimensional model with one and two active scalars respectively. Uplifting the first, one gets a dyonic string solution in D = 6 that has been known for a long time. Whereas, uplifting the second solution, one finds a very interesting configuration where magnetic strings are located uniformly on a circle in a plane within the 4-dimensional flat transverse space and electric strings are distributed homogeneously inside this circle. Both solutions have AdS3 × S3 limits.

Classification of String Solutions for the Self-Dual Einstein–Maxwell–Higgs Model

In this paper, we are concerned with an elliptic system arising from the Einstein–Maxwell–Higgs model which describes electromagnetic dynamics coupled with gravitational fields in spacetime. Reducing this system to a single equation and setting up the radial ansatz, we classify solutions into three cases: topological solutions, nontopological solutions of type I, and nontopological solutions of type II. There are two important constants: $$a>0$$ representing the gravitational constant and $$N\ge 0$$ representing the total string number. When $$0\le aN<2$$ , we give a complete classification of all possible solutions and prove the uniqueness of solutions for a given decay rate. In particular, we obtain a new class of topological solitons, with nonstandard asymptotic value $$\sigma <0$$ at infinity, when the total string number is sufficiently large such that $$1<aN<2$$ . We also prove the multiple existence of solutions for a given decay rate in the case $$aN \ge 2$$ . Our classification improves previous results which are known only for the case $$0<aN<1$$ .

Global half-BPS AdS2 \xd7 S6 solutions in Type IIB

We investigate half-BPS Type IIB supergravity solutions with spacetime geometry AdS2 × S6 warped over a Riemann surface Σ. The general local solution was obtained in earlier work in terms of two holomorphic functions {mathcal{A}}_{pm } on Σ. In the first part of this paper we seek global solutions corresponding to the near-horizon behavior of (p, q)-string junctions. We identify the type of singularity in {mathcal{A}}_{pm } needed at the boundary of Σ to match the solutions locally onto the classic (p, q)-string solution. We construct solutions with multiple (p, q)-strings, but the existence of geodesically complete solutions remains unsettled. In a second part we construct multi-parameter families of non-compact globally regular and geodesically complete solutions with asymptotic regions and an AdS2 throat which caps off smoothly.

Review of Differential Power Processing Converter Techniques for Photovoltaic Applications

Differential power processing (DPP) converters are utilized in photovoltaic (PV) power systems to achieve high-efficiency power output, even under uneven lighting or mismatched PV cell situations. Since this DPP concept has been introduced for PV systems, various topologies and control algorithms have been proposed and validated, showing the benefits of DPP converters systems over existing series string and full power processing converter solutions. However, DPP systems are highly coupled and can be challenging to control. Various architectures, topologies, and control strategies for both series and parallel DPP architectures are reviewed and compared. Tradeoffs of different DPP converters and topologies are discussed. Also, the power curve for the PV connected to bus, PV to PV, and PV to independent port series DPP architectures are evaluated in terms of inverter interaction. To date, the PV to PV series DPP systems have been most widely implemented and robust system-level control for all architectures has been a major research focus. Furthermore, research and development is still needed, particularly for commercialization and parallel DPP approaches for emerging PV applications.

Bethe-ansatz analysis of near-resonant two-component systems in one dimension

We introduce a new type of models for two-component systems in one dimension subject to exact solutions by Bethe ansatz, where the interspecies interactions are tunable via Feshbach resonant interactions. The applicability of Bethe ansatz is obtained by fine-tuning the resonant energies, and the resulting systems can be described by introducing intraspecies repulsive and interspecies attractive couplings $c_1$ and $c_2$. This kind of systems admits two types of interesting solutions: In the regime with $c_1>c_2$, the ground state is a Fermi sea of two-strings, where the Fermi momentum $Q$ is constrained to be smaller than a certain value $Q^*$, and it provides an ideal scenario to realize BCS-BEC crossover (from weakly attractive atoms to weakly repulsive molecules) in one dimension; In the opposite regime with $c_1<c_2$, the ground state is a single bright soliton even for fermionic atoms, which reveals itself as an embedded string solution.