String Solutions Research Articles

The action of long strings in supersymmetric field theories

Long strings emerge in many Quantum Field Theories, for example as vortices in Abelian Higgs theories, or flux tubes in Yang-Mills theories. The actions of such objects can be expanded in the number of derivatives, around a long straight string solution. This corresponds to the expansion of energy levels in powers of 1/L, with L the length of the string. Doing so reveals that the first few terms in the expansions are universal, and only from a certain term do they become dependent on the originating field theory. Such classifications have been made before for bosonic strings. In this work we expand upon that and classify also strings with fermionic degrees of freedom, where the string breaks D = 4, N = 1 SUSY completely. An example is the confining string in N = 1 SYM theory. We find a general method for generating supersymmetric action terms from their bosonic counterparts, as well as new fermionic terms which do not exist in the non-supersymmetric case. These terms lead to energy corrections at a lower order in 1/L than in the bosonic case.

On an Exact Cylindrically Symmetric Solution in a Born-Infeld Type Theory of Gravity

In this work, we derive an exact vacuum solution for a cylindrically symmetric metric in an extended gravity theory developed by Novello, De Lorenci and Luciane (hereafter referred to as the NDL theory) which is inspired in the Born-Infeld theory. The main goal of this paper is to nd a cosmic string solution for the NDL theory. However, a careful analysis of the metric shows that it is asymptotically singular and therefore does not represent a cosmic string solution.

Exotic branes in Exceptional Field Theory: E7(7) and beyond

In recent years, it has been widely argued that the duality transformations of string and M-theory naturally imply the existence of so-called ‘exotic branes’ — low codimension objects with highly non-perturbative tensions, scaling as gsα for α ≤ −3. We argue that their intimate link with these duality transformations make them an ideal object of study using the general framework of Double Field Theory (DFT) and Exceptional Field Theory (EFT) — collectively referred to as ExFT. Parallel to the theme of dualities, we also stress that these theories unify known solutions in string- and M-theory into a single solution under ExFT. We argue that not only is there a natural unifying description of the lowest codimension objects, many of these exotic states require this formalism as a consistent supergravity description does not exist.

Bubbling string solutions for the self-dual Einstein–Maxwell–Higgs equation

In this article, we establish the existence of type I nontopological bubbling solutions for the Einstein–Maxwell–Higgs equation in R 2 . Our solutions bubble at some string points and the local profile near those points comes from the radially symmetric solutions. We also prove that such bubbling solutions cannot exist on compact surfaces.

Elliptic string solutions on mathbb {R}times hbox {S}^2 and their pohlmeyer reduction

We study classical string solutions on mathbb {R}times hbox {S}^2 that correspond to elliptic solutions of the sine-Gordon equation. In this work, these solutions are systematically derived by inverting the Pohlmeyer reduction. A mapping of the physical properties of the string solutions to those of their Pohlmeyer counterparts is established. An interesting element of this mapping is the association of the number of spikes of the string to the topological charge in the sine-Gordon theory. Finally, the adopted parametrization of the solutions facilitates the identification of a dense subset of the moduli space of solutions, where the dispersion relation can be expressed in a closed form, arbitrarily far from the infinite size limit.

Homogeneous black strings in Einstein\u2013Gauss\u2013Bonnet with Horndeski hair and beyond

In this paper we construct new exact solutions in Einstein–Gauss–Bonnet and Lovelock gravity, describing asymptotically flat black strings. The solutions exist also under the inclusion of a cosmological term in the action, and are supported by scalar fields with finite energy density, which are linear along the extended direction and have kinetic terms constructed out from Lovelock tensors. The divergenceless nature of the Lovelock tensors in the kinetic terms ensures that the whole theory is second order. For spherically, hyperbolic and planar symmetric spacetimes on the string, we obtain an effective Wheeler’s polynomial which determines the lapse function up to an algebraic equation. For the sake of concreteness, we explicitly show the existence of a family of asymptotically flat black strings in six dimensions, as well as asymptotically hbox {AdS}_{5}times mathbb {R} black string solutions and compute the temperature, mass density and entropy density. We compute the latter by Wald’s formula and show that it receives a contribution from the non-minimal kinetic coupling of the matter part, shifting the one-quarter factor coming from the Einstein term, on top of the usual non areal contribution arising from the quadratic Gauss–Bonnet term. Finally, for a special value of the couplings of the theory in six dimensions, we construct strings that contain asymptotically AdS wormholes as well as rotating solutions on the transverse section. By including more scalars the strings can be extended to p-branes, in arbitrary dimensions.

AdS5 black strings in the stu model of FI-gauged N = 2 supergravity

We analytically construct asymptotically AdS5 black string solutions starting from the four-dimensional domain wall black hole of [1]. It is shown that its uplift gives a black string in d = 5 minimal gauged supergravity, with momentum along the string. Applying instead the residual symmetries of N = 2, d = 4 Fayet-Iliopoulos-gauged super-gravity discovered in [2] to the domain wall seed leads, after uplifting, to a dyonic black string that interpolates between AdS5 and AdS3 × H2 at the horizon. A Kaluza-Klein reduction of the latter along an angular Killing direction ϕ followed by a duality transformation yields, after going back to five dimensions, a black string with both momentum along the string and rotation along ϕ. This is the first instance of using solution-generating techniques in gauged supergravity to add rotation to a given seed. These solutions all have constant scalar fields. As was shown in [3], the construction of supersymmetric static magnetic black strings in the FI-gauged stu model amounts to solving the SO(2, 1) spinning top equations, which descend from an inhomogeneous version of the Nahm equations. We are able to solve these in a particular case, which leads to a generalization of the Maldacena-Nuñez solution.

Holographic three-point correlators in the Schrodinger/dipole CFT correspondence

We calculate, for the first time, three-point correlation functions involving “heavy” operators in the Schrodinger/null-dipole CFT correspondence at strong coupling. In particular, we focus on the three-point functions of the dilaton modes and two “heavy” operators. The heavy states are dual to the single spin and dyonic magnon, the single spin and dyonic spike solutions or to two novel string solutions which do not have an undeformed counterpart. Our results provide the leading term of the correlators in the large λ expansion and are in perfect agreement with the form of the correlator dictated by non-relativistic conformal invariance. We also specify the scaling function which can not be fixed by using conformal invariance.

Tau-Structure for the Double Ramification Hierarchies

In this paper we continue the study of the double ramification hierarchy of [Bur15]. After showing that the DR hierarchy satisfies tau-symmetry we define its partition function as the (logarithm of the) tau-function of the string solution and show that it satisfies various properties (string, dilaton and divisor equations plus some important degree constraints). We then formulate a stronger version of the conjecture from [Bur15]: for any semisimple cohomological field theory, the Dubrovin-Zhang and double ramification hierarchies are related by a normal (i.e. preserving the tau-structure [DLYZ14]) Miura transformation which we completely identify in terms of the partition function of the CohFT. In fact, using only the partition functions, the conjecture can be formulated even in the non-semisimple case (where the Dubrovin-Zhang hierarchy is not defined). We then prove this conjecture for various CohFTs (trivial CohFT, Hodge class, Gromov-Witten theory of $\mathbb{CP}^1$, $3$-, $4$- and $5$-spin classes) and in genus $1$ for any semisimple CohFT. Finally we prove that the higher genus part of the DR hierarchy is basically trivial for the Gromov-Witten theory of smooth varieties with non-positive first Chern class and their analogue in Fan-Jarvis-Ruan-Witten quantum singularity theory [FJRW].

Charged black strings and black branes in Lovelock theories

It is well known that the Reissner-Norstrom solution of Einstein-Maxwell theory cannot be cylindrically extended to higher dimension, as with the black hole solutions in vacuum. In this paper we show that this result is circumvented in Lovelock gravity. We prove that the theory containing only the quadratic Lovelock term, the Gauss-Bonnet term, minimally coupled to a $U(1)$ field, admits homogeneous black string and black brane solutions characterized by the mass, charge and volume of the flat directions. We also show that theories containing a single Lovelock term of order $n$ in the Lagrangian coupled to a $(p-1)$-form field admit simple oxidations only when $n$ equals $p$, giving rise to new, exact, charged black branes in higher curvature gravity. For General Relativity this stands for a Lagrangian containing the Einstein-Hilbert term coupled to a massless scalar field, and no-hair theorems in this case forbid the existence of black branes. In all these cases the field equations acquire an invariance under a global scaling scale transformation of the metric. As explicit examples we construct new magnetically charged black branes for cubic Lovelock theory coupled to a Kalb-Ramond field in dimensions $(3m+2)+q$, with $m$ and $q$ integers, and the latter denoting the number of extended flat directions. We also construct dyonic solutions in quartic Lovelock theory in dimension $(4m+2)+q$.

T-duality to scattering amplitude and Wilson loop in non-commutative super Yang-Mills theory

We first perform bosonic T-duality transformation on one of the marginal TsT (T-duality, shift, T-duality)-deformed AdS5×S5 spacetime, which corresponds to 4D mathcal{N}=4 non-commutative super Yang-Mills theory (NCSYM). We then construct the solution to Killing spinor equations of the resulting background, and perform the fermionic T-duality transformation. The final dual geometry becomes the usual AdS5 × S5 spacetime but with a constant NS-NS B-field depending on the non-commutative parameter. As applications, we study the gluon scattering amplitude and open string (Wilson loop) solution in the TsT-deformed AdS5 × S5 spacetime, which are dual to the null polygon Wilson loop and the folded string solution respectively in the final dual geometry.

Dressed elliptic string solutions on mathbb {R}times hbox {S}^2

We obtain classical string solutions on mathbb {R}^t times hbox {S}^2 by applying the dressing method on string solutions with elliptic Pohlmeyer counterparts. This is realized through the use of the simplest possible dressing factor, which possesses just a pair of poles lying on the unit circle. The latter is equivalent to the action of a single Bäcklund transformation on the corresponding sine-Gordon solutions. The obtained dressed elliptic strings present an interesting bifurcation of their qualitative characteristics at a specific value of a modulus of the seed solutions. Finally, an interesting generic feature of the dressed strings, which originates from the form of the simplest dressing factor and not from the specific seed solution, is the fact that they can be considered as drawn by an epicycle of constant radius whose center is running on the seed solution. The radius of the epicycle is directly related to the location of the poles of the dressing factor.

Semiclassical SL(2) strings on LLM backgrounds

We study semi-classical string solutions that live on white regions of the LLM plane for a generic LLM geometry. These string excitations are labelled by conserved charges E,J and S and are thus holographically dual to operators in the SL(2) sector of N=4 super Yang–Mills made up of covariant derivatives acting on complex scalar fields Z. On the other hand, the LLM geometry itself is dual to an operator consisting of O(N2)Z-fields so that the operators dual to our solutions, containing both the stringy excitation and background, are non-planar. In an appropriate short string limit we argue that the string solution we find should be dual to a localised SL(2) operator in the gauge theory language. This allows us to perform a non-trivial check of the recent proposal that the dynamics of localised operators should be identical, up to a rescaling of the 't Hooft coupling, to the dynamics of those same excitations in the AdS5×S5 background.

Renormalization in large-N QCD is incompatible with open/closed string duality

Solving by a canonical string theory, of closed strings for the glueballs and open strings for the mesons, the 't Hooft large-N expansion of QCD is a long-standing problem that resisted all the attempts despite the advent of the celebrated gauge/gravity duality in the framework of string theory. We demonstrate that in the canonical string framework such a solution does not actually exist because an inconsistency arises between the renormalization properties of the QCD S matrix at large N, recently worked out in Bochicchio (2017) [5], and the open/closed duality of the would-be string solution. Specifically, the would-be open-string one-loop corrections to the tree glueball amplitudes must be ultraviolet (UV) divergent by the aforementioned renormalization properties, which follow from the QCD asymptotic freedom (AF) and renormalization group. Hence, naively, the inconsistency arises because these amplitudes are dual to tree closed-string diagrams, which are universally believed to be both UV finite – since they are closed-string tree diagrams – and infrared (IR) finite because of the glueball mass gap. In fact, the inconsistency follows from a low-energy theorem of the Novikov–Shifman–Vainshtein–Zakharov (NSVZ) type derived in Bochicchio (2017) [5] that controls the renormalization in QCD-like theories. The aforementioned inconsistency extends to the would-be canonical string for a vast class of 't Hooft large-N confining asymptotically free QCD-like theories including N=1 SUSY QCD. We also demonstrate that the presently existing SUSY string models with a mass gap based on the gauge/gravity duality– such as Klebanov–Strassler, Polchinski–Strassler (PS) and certain PS variants – cannot contradict the above-mentioned results, not even potentially, since they are not asymptotically free. Moreover, we shed light on the way the open/closed string duality may be perturbatively realized in these string models compatibly with a mass gap in the 't Hooft-planar closed-string sector and the aforementioned low-energy theorem because of the lack of AF. Finally, we suggest a noncanonical way-out for asymptotically free QCD-like theories based on topological strings on noncommutative twistor space.

T-duality and high-derivative gravity theories: the BTZ black hole/string paradigm

We show that the temperature and entropy of a BTZ black hole are invariant under T-duality to next to leading order in M⋆− 2, M⋆ being the scale suppressing higher-curvature/derivative terms in the Lagrangian. We work in the framework of a twoparameter family of theories exhibiting T-duality, which includes (but goes beyond) String Theory. Interestingly enough, the AdS/CFT correspondence enforces quantization conditions on these parameters. In the particular case of bosonic/heterotic string theory, our results extend those of a classical paper by Horowitz and Welch. For generic (albeit quantized) values of the parameters, it suggests that T-duality might be an interesting tool to constrain consistent low-energy effective actions while entailing physical equivalences outside String Theory. Moreover, it generates a new family of regular asymptotically flat black string solutions in three-dimensions.

BPS solutions of six-dimensional (1, 0) supergravity coupled to tensor multiplets

We derive a general local form for supersymmetric solutions of six-dimensional (1, 0) supergravity coupled to an arbitrary number of tensor multiplets. We consider some special cases in which the resulting equations can be solved explicitly. In particular we derive black string solutions and calculate their entropy. Upon reducing to five dimensions they yield spinning black hole solutions. We also discuss BPS pp-waves and black string solutions with traveling waves. Lastly, as an application, we study the attractor mechanism in this theory.

Phases and stability of non-uniform black strings

We construct solutions of non-uniform black strings in dimensions from D ≈ 9 all the way up to D = ∞, and investigate their thermodynamics and dynamical stability. Our approach employs the large-D perturbative expansion beyond the leading order, including corrections up to 1/D4. Combining both analytical techniques and relatively simple numerical solution of ODEs, we map out the ranges of parameters in which non-uniform black strings exist in each dimension and compute their thermodynamics and quasinormal modes with accuracy. We establish with very good precision the existence of Sorkin’s critical dimension and we prove that not only the thermodynamic stability, but also the dynamic stability of the solutions changes at it.

Modelling vibrating nano-strings by lattice, finite difference and Eringen's nonlocal models

This paper focuses on the modelling of a tightly stretched nano-string with elastically supported ends by the central finite difference model (FDM), the lattice model and the Eringen's nonlocal model (ENM). The equivalence between the FDM and the lattice model is confirmed provided that the nodal spacing of FDM is equal to the segmental length of lattice model. The analytical vibration solutions for lattice model or FDM can be obtained by solving the linear second-order finite difference equation derived herein. By matching the vibration solutions for lattice model (or FDM) and ENM, the Eringen's small length scale coefficient e0 is calibrated, which is a constant equal to 0.289, regardless of the vibration modes or boundary conditions. The influence of end lateral spring stiffnesses on the vibration solutions for a taut local string is also discussed. For a taut symmetrically restrained local string with sliding ends, the fundamental frequency always approaches to zero and the second frequency always approaches to π.

Straight spinning cosmic strings in Brans–Dicke gravity

An exact solution of straight spinning cosmic strings in Brans–Dicke theory of gravitation is presented. The possibility of the existence of closed time-like curves around these cosmic strings is analyzed. Furthermore, the stability about the formation of the topological defect discussed here is checked. It is shown that the existence of a suitable choice for the integration constants in which closed time-like curves are not allowed. We also study the (im)possibility of using the obtained spacetime in the rotational curves problem.

Statics of Shallow Inclined Elastic Cables under General Vertical Loads: A Perturbation Approach

The static problem for elastic shallow cables suspended at points at different levels under general vertical loads is addressed. The cases of both suspended and taut cables are considered. The funicular equation and the compatibility condition, well known in literature, are here shortly re-derived, and the commonly accepted simplified hypotheses are recalled. Furthermore, with the aim of obtaining simple asymptotic expressions with a desired degree of accuracy, a perturbation method is designed, using the taut string solution as the generator system. The method is able to solve the static problem for any distributions of vertical loads and shows that the usual, simplified analysis is just the first step of the perturbation procedure proposed here.