Circular String Research Articles

Electrified BPS giants: BPS configurations on giant gravitons with static electric field

We consider D3-brane action in the maximally supersymmetric type IIB plane-wave background. Upon fixing the light-cone gauge, we obtain the light-cone Hamiltonian which is manifestly supersymmetric. The 1/2 BPS solutions of this theory (solutions which preserve 16 supercharges) are either of the form of spherical three branes, the giant gravitons, or zero size point like branes. We then construct specific classes of 1/4 BPS solutions of this theory in which static electric field on the brane is turned on. These solutions are deformations about either of the two 1/2 BPS solutions. In particular, we study in some detail 1/4 BPS configurations with electric dipole on the three sphere giant, i.e. BIons on the giant gravitons, which we hence call BIGGons. We also study BPS configurations corresponding to turning on a background uniform constant electric field. As a result of this background electric field the three sphere giant is deformed to squashed sphere, while the zero size point like branes turn into circular or straight fundamental strings in the plane-wave background, with their tension equal to the background electric field.

The [formula omitted] superstring quantum spectrum from the algebraic curve

We propose a method for computing the energy level spacing around classical string solutions in AdS 5 × S 5 . This method is based on the integrable structure of the string and can be applied to an arbitrary classical configuration. Our approach treats in equal footing the bosonic and fermionic excitations and provides an unambiguous prescription for the labeling of the fluctuation frequencies. Finally we revisit the computation of these frequencies for the SU ( 2 ) and SL ( 2 ) circular strings and compare our results to the existing ones.

Dual spikes—New spiky string solutions

We find a new class of spiky solutions for closed strings in flat, $AdS_3\subset AdS_5$ and $R\times S^2(\subset S^5)$ backgrounds. In the flat case the new solutions turn out to be T-dual configurations of spiky strings found by Kruczenski hep-th/0410226. In the case of solutions living in $AdS$, we make a semi classical analysis by taking the large angular momentum limit. The anomalous dimension for these dual spikes is similar to that for rotating and pulsating circular strings in AdS with angular momentum playing the role of the level number. This replaces the well known logarithmic dependence for spinning strings. For the dual spikes living on sphere we find that no large angular momentum limit exists.

Cylindrically symmetric solitons in Einstein-Yang-Mills theory

Recently new Einstein-Yang-Mills (EYM) soliton solutions were presented which describe superconducting strings with Kasner asymptotics [D. V. Gal'tsov, E. A. Davydov, and M. S. Volkov, hep-th/0610183.]. Here we study the static cylindrically symmetric SU(2) EYM system in more detail. The ansatz for the gauge field corresponds to superposition of the azimuthal ${B}_{\ensuremath{\varphi}}$ and the longitudinal ${B}_{z}$ components of the color magnetic field. We derive sum rules relating data on the symmetry axis to asymptotic data and show that generic asymptotic structure of regular solutions is Kasner. Solutions starting with vacuum data on the axis generically are divergent. Regular solutions correspond to some bifurcation manifold in the space of parameters which has the low-energy limiting point corresponding to string solutions in flat space (with the divergent total energy) and the high-curvature point where gravity is crucial. Some analytical results are presented for the low-energy limit, and numerical bifurcation curves are constructed in the gravitating case. Depending on the parameters, the solution looks like a straight string or a pair of straight and circular strings. The existence of such nonlinear superposition of two strings becomes possible due to self-interaction terms in the Yang-Mills action which suppress contribution of the circular string near the polar axis.

Infinite spin limit of semiclassical string states

Motivated by recent works of Hofman and Maldacena and Dorey we consider a special infinite spin limit of semiclassical spinning string states in AdS5 x S5. We discuss examples of known folded and circular 2-spin string solutions and demonstrate explicitly that the 1-loop superstring correction to the classical expression for the energy vanishes in the limit when one of the spins is much larger that the other. We also give a general discussion of this limit at the level of integral equations describing finite gap solutions of the string sigma model and argue that the corresponding asymptotic form of the string and gauge Bethe equations is the same.

The SU(1|2) and SU(2|2) sectors from superstrings inAdS5×S5

For the \kappa-symmetry gauge fixed superstring action in AdS_5 x S^5 we consider the fermionic fluctuations over a circular bosonic string background with two angular momenta and two winding numbers in S^5. The SU(2)-type redefinitions of fermionic fields and the first-string limit generate a truncated fermionic action for the SU(1|2) sector. It is expressed in a two-dimensional Lorentz-invariant form of a massive Dirac fermion and the plane-wave spectrum for the fermionic excitations is derived. The fermionic spectrum for the SU(2|2) sector is also analyzed.

Handbook on string decay

We explain simple semi-classical rules to estimate the lifetime of any given highly-excited quantum state of the string spectrum in flat spacetime. We discuss both the decays by splitting into two massive states and by massless emission. As an application, we study a solution describing a rotating and pulsating ellipse which becomes folded at an instant of time -- the ``squashing ellipse''. This string interpolates between the folded string with maximum angular momentum and the pulsating circular string. We explicitly compute the quantum decay rate for the corresponding quantum state, and verify the basic rules that we propose. Finally, we give a more general (4-parameter) family of closed string solutions representing rotating and pulsating elliptical strings.

Spinning Strings and Integrable Spin Chains in the AdS/CFT Correspondence.

In this introductory review we discuss dynamical tests of the AdS5 × S5 string/{mathcal N}=4 Super Yang-Mills duality. After a brief introduction to AdS/CFT, we argue that semiclassical string energies yield information on the quantum spectrum of the string in the limit of large angular momenta on the S5. The energies of the folded and circular spinning string solutions rotating on a S3 within the S5 are derived, which yield all-loop predictions for the dual gauge theory scaling dimensions. These follow from the eigenvalues of the dilatation operator of {mathcal N}=4 Super Yang-Mills in a minimal SU(2) subsector, and we display its reformulation in terms of a Heisenberg s = 1/2 spin chain along with the coordinate Bethe ansatz for its explicit diagonalization. In order to make contact to the spinning string energies, we then study the thermodynamic limit of the one-loop gauge theory Bethe equations and demonstrate the matching with the folded and closed string result at this loop order. Finally, the known gauge theory results at higher-loop orders are reviewed and the associated long-range spin chain Bethe ansatz is introduced, leading to an asymptotic all-loop conjecture for the gauge theory Bethe equations. This uncovers discrepancies at the three-loop order between gauge theory scaling dimensions and string theory energies and the implications of this are discussed. Along the way, we comment on further developments and generalizations of the subject and point to the relevant literature.

1/J2corrections to BMN energies from the quantum long range Landau-Lifshitz model

In a previous paper (hep-th/0509071), it was shown that quantum 1/J corrections to the BMN spectrum in an effective Landau-Lifshitz (LL) model match with the results from the one-loop gauge theory, provided one chooses an appropriate regularization. In this paper we continue this study for the conjectured Bethe ansatz for the long range spin chain representing perturbative planar N=4 Super Yang-Mills in the SU(2) sector, and the ``quantum string" Bethe ansatz for its string dual. The comparison is carried out for corrections to BMN energies up to 3rd order in the effective expansion parameter $\tl=\lambda/J^2$. After determining the ``gauge-theory'' LL action to order $\tl^3$, which is accomplished indirectly by fixing the coefficients in the LL action so that the energies of circular strings match with the energies found using the Bethe ansatz, we find perfect agreement. We interpret this as further support for an underlying integrability of the system. We then consider the ``string-theory'' LL action which is a limit of the classical string action representing fast string motion on an S^3 subspace of S^5 and compare the resulting $\tl^3/J^2$ corrections to the prediction of the ``string'' Bethe ansatz. As in the gauge case, we find precise matching. This indicates that the LL Hamiltonian supplemented with a normal ordering prescription and zeta-function regularization reproduces the full superstring result for the $1/J^2$ corrections, and also signifies that the string Bethe ansatz does describe the quantum BMN string spectrum to order $1/J^2$. We also comment on using the quantum LL approach to determine the non-analytic contributions in $\lambda$ that are behind the strong to weak coupling interpolation between the string and gauge results.

Spinning strings on deformedAdS5×T1,1with Neveu-SchwarzBfield

We study classical spinning closed string configuration on logarithmically deformed AdS_5 x T^{1,1} background with non-trivial Neveu-Schwarz B-field in which IIB string theory is dual to a non-conformal N=1 SU(N+M) x SU(N) gauge theory. The integrability on original AdS_5 x T^{1,1} background are significantly reduced by B-field. We find several spinning string solutions with two different ansatzs. Solutions for point-like strings and few circular strings are explicitly obtained. Folded spinning string solutions along radial direction are shown to be allowed in this background. These solutions exhibit novel properties and bring some challenges to understand them from dual quantum field theory.

Semiclassical circular strings inAdS5and “long” gauge field strength operators

We consider circular strings rotating with equal spins ${S}_{1}={S}_{2}=S$ in two orthogonal planes in $Ad{S}_{5}$ and suggest that they may be dual to long gauge-theory operators built out of self-dual components of gauge field strength. As was found in hep-th/0404187, the one-loop anomalous dimensions of the such gauge-theory operators are described by an antiferromagnetic ${\mathrm{XXX}}_{1}$ spin chain and scale linearly with length $L\ensuremath{\gg}1$. We find that in the case of rigid rotating string both the classical energy ${E}_{0}$ and the 1-loop string correction ${E}_{1}$ depend linearly on the spin $S$ (within the stability region of the solution). This supports the identification of the rigid rotating string with the gauge-theory operator corresponding to the maximal-spin (ferromagnetic) state of the ${\mathrm{XXX}}_{1}$ spin chain. The energy of more general rotating and pulsating strings also happens to scale linearly with both the spin and the oscillation number. Such solutions should be dual to other lower-spin states of the spin chain, with the antiferromagnetic ground state presumably corresponding to the string pulsating in two planes with no rotation.

Spinning strings in AdS5 × S5: one-loop correction to energy in SL(2) sector

We consider a circular string with spin $S$ in $AdS_5$ wrapped around big circle of $S^5$ and carrying also momentum $J$. The corresponding N=4 SYM operator belongs to the SL(2) sector, i.e. has tr$(D^S Z^J)+...$ structure. The leading large $J$ term in its 1-loop anomalous dimension can be computed using Bethe ansatz for the SL(2) spin chain and was previously found to match the leading term in the classical string energy. The string solution is stable at large $J$, and the Lagrangian for string fluctuations has constant coefficients, so that the 1-loop string correction to the energy $E_1$ is given simply by the sum of characteristic frequencies. Curiously, we find that the leading term in the zero-mode part of $E_1$ is the same as a 1/J correction to the one-loop anomalous dimension on the gauge theory (spin chain) side that was found in hep-th/0410105. However, the contribution of non-zero string modes does not vanish. We also discuss the ``fast string'' expansion of the classical string action which coincides with the coherent state action of the SL(2) spin chain at the first order in $\l$, and extend this expansion to higher orders clarifying the role of the $S^5$ winding number.

Tubular Solutions in NS5-brane, Dp-brane and Macroscopic Strings Backgrounds

We present our searches for the tubular bound states of a D2-brane with $m$ D0-branes and $n$ fundamental strings in the NS5-brane, Dp-brane or macroscopic strings background by solving the Dirac-Born-Infeld equation. The geometry of tubular configurations we considered are taken to be parallel to the background branes or macroscopic strings. The $n$ fundamental strings therein may be the circular strings $F_c$ or the straight strings $F_s$, which are along the cross section or the axis of the tube respectively. We show that the stable tubular bound states of ($nF_s$, $m$D0, D2) which are prevented form collapse by the angular momentum, as original found in flat space, could be formed in the NS5-brane, D6-brane and macroscopic strings background. However, they becomes unstable in the D2-brane and D4-brane background. We also show that there are stable tubular bound states of ($nF_c$, $m$D0, D2) and ($m$D0, D2), which are prevented form collapse by the gravitational forces in the backgrounds of D6-brane. We discuss the properties of these tubular solutions and see that only that in the macroscopic strings background is a supersymmetric BPS configuration.

Semiclassical String Solutions on 1/2 BPS Geometries

We study semiclassical string solutions on the 1/2 BPS geometry of type IIB string theory characterized by concentric rings on the boundary plane. We consider both folded rotating strings carrying nonzero R-charge and circular pulsating strings. We find that unlike rotating strings, as far as circular pulsating strings are concerned, the dynamics remains qualitatively unchanged when the concentric rings replace AdS_5\times S^5. Using the gravity dual we have also studied the Wilson loop of the corresponding gauge theory. The result is qualitatively the same as that in AdS_5\times S^5 in the global coordinates where the corresponding gauge theory is defined on S^3\times R. We show that there is a correction to 1/L leading order behavior of the potential between external objects.

One-loop correction to the energy of spinning strings inS5

We revisit the computation (hep-th/0306130) of 1-loop AdS_5 x S^5 superstring sigma model correction to energy of a closed circular string rotating in S^5. The string is spinning around its center of mass with two equal angular momenta J_2=J_3 and its center of mass angular momentum is J_1. We revise the argument in hep-th/0306130 that the 1-loop correction is suppressed by 1/J factor (J= J_1 + 2 J_2 is the total SO(6) spin) relative to the classical term in the energy and use numerical methods to compute the leading 1-loop coefficient. The corresponding gauge theory result is known (hep-th/0405055) only in the J_1=0 limit when the string solution becomes unstable and thus the 1-loop shift of the energy formally contains an imaginary part. While the comparison with gauge theory may not be well-defined in this case, our numerical string theory value of the 1-loop coefficient seems to disagree with the gauge theory one. A plausible explanation should be (as in hep-th/0405001) in the different order of limits taken on the gauge theory and the string theory sides of the AdS/CFT duality.

Search for the most stable massive state in superstring theory

In ten dimensional type II superstring, all perturbative massive states are unstable, typically with a short lifetime compared to the string scale. We find that the lifetime of the average string state of mass M has the asymptotic form T < const.1/(g^2 M). The most stable string state seems to be a certain state with high angular momentum which can be classically viewed as a circular string rotating in several planes ("the rotating ring"), predominantly decaying by radiating soft massless NS-NS particles, with a lifetime T = c_0 M^5/g^2. Remarkably, the dominant channel is the decay into a similar rotating ring state of smaller mass. The total lifetime to shrink to zero size is ~ M^7. In the presence of D branes, decay channels involving open strings in the final state are exponentially suppressed, so the lifetime is still proportional to M^5, except for a D brane at a special angle or flux. For large mass, the spectrum for massless emission exhibits qualitative features typical of a thermal spectrum, such as a maximum and an exponential tail. We also discuss the decay properties of rotating rings in the case of compact dimensions.

Rotating black hole, twistor-string and spinning particle

We discuss basic features of the model of spinning particle based on the Kerr solution. It contains a very nontrivial {\it real} stringy structure consisting of the Kerr circular string and an axial stringy system. We consider also the complex and twistorial structures of the Kerr geometry and show that there is a {\it complex} twistor-string built of the complex N=2 chiral string with a twistorial $(x,\theta)$ structure. By imbedding into the real Minkowski $\bf M^4$, the N=2 supersymmetry is partially broken and string acquires the open ends. Orientifolding this string, we identify the chiral and antichiral structures. Target space of this string is equivalent to the Witten's `diagonal' of the $\bf CP^3\times CP^{*3}.$

Circular and Folded Multi-Spin Strings in Spin Chain Sigma Models

From the SU(2) spin chain sigma model at the one-loop and two-loop orders we recover the classical circular string solution with two S5 spins (J1,J2) in the AdS5 ? S5 string theory. In the SL(2) sector of the one-loop spin chain sigma model we explicitly construct a solution which corresponds to the folded string solution with one AdS5 spin S and one S5 spin J. In the one-loop general sigma model we demonstrate that there exists a solution which reproduces the energy of the circular constant-radii string solution with three spins (S1,S2,J).

Higher Loops Beyond the SU(2) Sector

We consider the case of coherent gauge invariant operators in the SU(3) and SO(4) sectors. We argue that in many cases, these sectors can be closed in the thermodynamic limit, even at higher loops. We then use a modification of the Bethe equations which is a natural generalization of a proposal put forward by Serban and Staudacher to make gauge theory predictions for the anomalous dimensions for a certain class of operators in each sector. We show that the predictions are consistent with semiclassical string predictions at two loops but in general fail to agree at three loops. Interestingly, in both cases there is one point in the configuration space where the gauge theory and string theory predictions agree. In the SU(3) case it corresponds to a circular string with R-charge assignment (J,J,J).

Twistorial analyticity and three stringy systems of the Kerr spinning particle

The Kerr spinning particle has a remarkable analytical twistorial structure. Analyzing electromagnetic excitations of the Kerr circular string which are aligned to this structure, we obtain a simple stringy skeleton of the spinning particle which is formed by a topological coupling of the Kerr circular singular string and by an axial singular stringy system. We show that the chiral traveling waves, related to an orientifold world-sheet of the axial stringy system, are described by the massive Dirac equation, so we argue that the axial string may play the part of a stringy carrier of wave function and play also a dominant role in the scattering processes. A key role of the third, {\it complex} Kerr string is discussed. We conjecture that it may be one more alternative to the Witten twistor string, and a relation to the spinor helicity formalism is also discussed.