In the light of $ϕ$-mapping topological current theory, the structure of cosmic strings are obtained from the Abelian Higgs model, which is an effective description to the brane world cosmic string system. In this topological description of the cosmic string, combining the result of decomposition of U(1) gauge potential, we analytically reach the familiar conclusions that in the brane world scenario the magnetic flux of the cosmic string is quantized and the RR charge of it is screened.
This paper is devoted to the study of dynamics of fundamental string and D1-brane in I-brane background. We consider configurations where string and D1-brane uniformly wrap transverse spheres. We explicitly determine corresponding conserved charges and find relations between them.
In this short note we formulate Covariant Hamiltonian formalism for strings, p-branes and Non-BPS Dp-branes. We also analyse the vacuum tachyon condensation in case of unstable D1-brane.
In this paper we would like to discuss the emergence of D-branes from infinite many D-instantons in bosonic and type IIA string theory in the framework of boundary string field theory.
We study the mass and different RR charge distributions of the BPS (p,p-2)-brane bound states in the closed string brane-like $σ$-model. We show that such brane bound states can be realized by introducing a constant B field in the closed string theory. In addition we show that the worldvolume coordinates of these brane bound states turn out to be noncommutative.
We generalize the ideas and formalism of Two-Time Physics from particle dynamics to some specific examples of string and p-brane (p >= 1) dynamics. The two-time string or p-brane action can be gauge fixed to produce various one-time string or p-brane actions that are dual to each other under gauge transformations. We discuss the particular gauges that correspond to tensionless strings and p-branes in flat (d-1)+1 spacetime, rigid strings and p-branes in flat (d-1)+1 spacetime, and tensionless strings and p-branes propagating in the AdS_{d-n} x S^n backgrounds.
We study fundamental string (F-string) dynamics near D5-brane in some limits. We find that when the angular momentum of the probe is proportional to string length (l_s) and square root of string coupling constant {g_s}, the F-string lies in its metastable orbit at a finite distance from D5-branes. We further study the metastable orbits of a M2-brane in M5-brane background.
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 prev…
The production of string charge during a crossing of certain oriented D-branes is studied. We compute the string charge in the system of a probe D2-brane and a background D6-brane by use of the equations of motion in the ten-dimensions. We confirm the creation of string charge as inflow from the background D6-brane.
We describe cosmic D--term strings as D3 branes wrapped on a resolved conifold. The matter content that gives rise to D--term strings is shown to describe the world--volume theory of a space--filling D3 brane transverse to the conifold which itself is a wrapped D5 brane. We show that, in this brane theory, the tension of the wrapped D3 brane mathces that of the D--term string. We argue that there is a new type of cosmic string which arises from fractional D1 branes on the world--volume of a fractional D3 brane.
We study dynamics of (m,n)-string in (p,q)-five brane and (p,q)-string background. We determine world-volume stress energy tensor and we analyze the dependence of the string's dynamics on the values of the charges (m,n) and the value of the angular momentum.
We consider eight-brane configurations in M(atrix) theory and compute their interaction potentials with gravitons, membranes, and four-branes. We compare these results with the interactions of D8-branes with D0-branes, D2-branes, and D4-branes in IIA string theory. We find agreement between the two approaches for eight-brane interactions with two-branes and four-branes. A discrepancy is noted in the case with zero-branes.
We study D-brane actions in non-relativistic string theory. We consider single D-brane and analyse its properties under T-duality. We also derive an action for N D8-branes and also for lower dimensional D-branes through T-duality transformations.
Brane actions with chiral bosons present special challenges. Recent progress in the description of the two main examples -- the M theory five-brane and the heterotic string -- is described. Also, double dimensional reduction of the M theory five-brane on K3 is shown to give the heterotic string.
A ghost D-brane has been proposed as an object that cancels the effects of a D-branes. We construct a classical solution with an arbitrary number of D-branes and ghost D-branes in the context of open string field theory. Cancellation of BRST cohomolgy between D-branes and ghost D-branes is shown.
We study the spectrum of open strings on AdS_2 branes in AdS_3 in an NS-NS background, using the SL(2,R) WZW model. When the brane carries no fundamental string charge, the open string spectrum is the holomorphic square root of the spectrum of closed strings in AdS_3. It contains short and long strings, and is invariant under spectral flow. When the brane carries fundamental string charge, the open string spectrum again contains short and long strings in all winding sectors. However, branes with fundamental string charge break half the spectral flow symmetry. This has different implications fo…
By using the non-supersymmetric $p$-brane solutions delocalized in arbitrary number of transverse directions in type II supergravities, we show how they can be regarded as interpolating solutions between unstable D$p$-branes (a non-BPS D-brane or a pair of coincident D-brane-antiD-brane) and fundamental strings and also between unstable D$p$-branes and NS5-branes. We also show that some of these solutions can be regarded as interpolating solutions between NS5/$\bar{\rm NS}$5 and D$p$-branes (for $p \leq 5$). This gives a closed string description of the tachyon condensation and lends support t…
We show that Dirichlet p-brane can be expressed as a configuration of infinitely many Dirichlet (p-2)-branes in the bosonic string theory. Using this fact, we interpret the massless fields on the p-brane worldvolume as deformations of the configuration of the (p-2)-branes. Especially we find that the worldvolume gauge field parametrizes part of the group of diffeomorphisms on the worldvolume.
Following the conjectured duality between near-horizon NS5-branes and little string theory, the string-corrected thermodynamics of near-horizon NS5-branes is studied and found to agree with the statistical thermodynamics of a 5+1 dimensional supersymmetric string theory near the Hagedorn temperature. Specifically, tree-level corrections to the temperature are argued to vanish, in accordance with the duality, while the one-loop string correction to the NS5-brane thermodynamics is shown to generate the correct temperature dependence of the entropy.
The compactness of the closed string in the classical Type II string theory reveals the duality, whereas the compactness of the open string reveals that the end of the string is on the hypersurface which satisfies the Dirichlet boundary condition.
The tremendous progress achieved through the study of black holes and branes suggests that their time dependent generalizations called Spacelike branes (S-branes) may prove similarly useful. An example of an established approach to S-branes is to include a string boundary interaction and we first summarize evidence for the death of open string degrees of freedom for the homogeneous rolling tachyon on a decaying brane. Then, we review how to extract the flat S-brane worldvolumes describing the homogeneous rolling tachyon and how large deformations correspond to creation of lower dimensional str…
Recent work on solutions to the Born-Infeld theory used to describe D-branes suggests that fundamental strings can be viewed, in a certain limit, as D-branes whose worldvolumes have collapsed to string-like configurations. Here we address the possibility of undoing this collapse, by inducing the string to tunnel to an extended brane configuration. Using semiclassical methods we argue that, by putting one of these Born-Infeld strings in the background of a uniform 4-form RR field strength, the string can nucleate a spheroidal bulge of D2-brane, or, if the string is wrapped around a small enough…
The covariant field equations of ten-dimensional super D-branes are obtained by considering fundamental strings whose ends lie in the superworldsurface of the D-brane. By considering in a similar fashion Dp-branes ending on D(p+2)-branes we derive equations describing D-branes with dual potentials, as well as the vector potentials.
D-brane configurations containing fundamental strings are constructed as classical solutions of Yang-Mills theory. The fundamental strings in these systems stretch between D-branes. In the case of D1-branes, this construction gives smooth (classical) resolutions of string junctions and string networks. Using a non-abelian Yang-Mills analysis of the string current, the string charge density is computed and is shown to have support in the region between the D-brane world-volumes. The 't Hooft-Polyakov monopole is analyzed using similar methods, and is shown to contain D-strings whose flux has su…
We review the recent developments in our understanding of non-BPS states and branes in string theory. The topics include 1) construction of unstable non-BPS D-branes in type IIA and type IIB string theories, 2) construction of stable non-BPS D-branes on various orbifolds and orientifolds of type II string theories, 3) description of BPS and non-BPS D-branes as tachyonic soliton solutions on brane-antibrane pair of higher dimension, and 4) study of the spectrum of non-BPS states and branes on a system of coincident D-brane - orientifold plane system. Some other related results are also discusse…
We investigate spectrum of open strings on D-branes after tachyon condensation in bosonic string theory. We calculate 1-loop partition function of the string and show that its limiting forms coincide with partition functions of open strings with different boundary conditions.
We construct non-relativistic string and p-brane actions in Newton-Cartan background using the limiting procedure from the relativistic string and p-brane action in general background. We also find their Hamiltonian formulations when however we restrict ourselves to the case of the vanishing gauge field.
This paper analyzes the effect of curved closed string backgrounds on the stability of D-branes within boundary string field theory. We identify the non-local open string background that implements shifts in the closed string background and analyze the tachyonic sector off-shell. The renormalization group flow reveals some characteristic properties, which are expected for a curved background, like the absence of a stable space-filling brane. In 3-dimensions we describe tachyon condensation processes to lower-dimensional branes, including a curved 2-dimensional brane. We argue that this 2-brane…
New exact string solutions in non-constant background fields are found and it is shown that some of them are compatible with the boundary conditions for the open string - D-brane system. Extension of the constraint algebra is proposed and discussed.
We examine the system where a string stretches between pair of D-branes, and study the bending of the D-brane caused by the tension of the string. If the distance between the pair of D-branes is sent to infinity, the tension of the string stretching between them is strong enough to pull the spike all the way to infinity. We study the shape of these spikes when the branes are finite distance apart using two different methods. First, we consider a string stretched between a pair of D2-branes in type IIA theory by going to the M-theory limit in which all of these branes are M-theory 2-branes embe…
In this paper we find D-brane descriptions of some of new open string solutions that were found in 0804.3438[hep-th]. These D5-brane and D3-brane configurations give gravitational dual descriptions of Wilson loops in some particular representations.
The thermodynamics of a gas of strings and D-branes near the Hagedorn transition is described by a coupled set of Boltzmann equations for weakly interacting open and closed long strings. The resulting distributions are dominated by the open string sector, indicating that D-branes grow to fill space at high temperature.
We study semiclassical strings in the near horizon geometry of certain curved branes. We investigate the rigidly rotating strings in the near horizon geometry of NS5-branes wrapped on AdS3 x S3 and in the presence of background NS-NS flux. We study several string solutions corresponding to giant magnon, single spike and more general folded strings for the fundamental string in this background. We comment that in the S-dual background the situation changes drastically.
We study the force balance between orthogonally positioned $p$-brane and $(8-p)$-brane. The force due to graviton and dilaton exchange is repulsive in this case. We identify the attractive force that balances this repulsion as due to one-half of a fundamental string stretched between the branes. As the $p$-brane passes through the $(8-p)$-brane, the connecting string changes direction, which may be interpreted as creation of one fundamental string. We show this directly from the structure of the Chern-Simons terms in the D-brane effective actions. We also discuss the effect of string creation …
We calculate the potential for $Dp-\Dbar p$ pair and show that the coincident $Dp-\Dbar p$ system has $(11-p)$ tachyonic modes, with $(9-p)$ of them due to radiative corrections. We propose that the decay width of an unstable non-BPS-$Dp$-brane to closed strings is given by the imaginary part of the one-loop contribution to the effective potential of the open string tachyon mode.
We discuss the BPS configurations of IIB strings in the 7-brane background from M-theory viewpoint. We first obtain the hyperkahler geometry background of M-theory expected from the 7-brane solutions of the type IIB supergravity. We choose the appropriate complex structures of the background geometries and embed a membrane of M-theory holomorphically to obtain a BPS string configuration. The recently discussed BPS string configurations such as 3-string junctions and string networks in the flat background are generalized to the cases with the 7-brane backgrounds. The property of the BPS string …
We review a number of perturbative calculations describing the interactions of D-branes with massless elementary string states. The form factors for the scattering of closed strings off D-branes are closely related to the Veneziano amplitude. They show that, in interactions with strings, D-branes acquire many of their physical features: the effective size of D-branes is of order the string scale and expands with the energy of the probe, while the fixed angle scattering amplitudes fall off exponentially. We also calculate the leading process responsible for the absorption of closed strings: the…
Lecture notes reviewing most recent developments in string/M/brane theory given by C. G. at the CIME Summer International Center of Mathematics at Cetraro. July 1997.
We apply the Dirac bracket quantization to open strings attached to branes in the presence of background antisymmetric field and recover an inherent noncommutativity in the internal coordinates of the brane.
We investigate the Penrose limit of various brane solutions including Dp-branes, NS5-branes, fundamental strings, (p,q) fivebranes and (p,q) strings. We obtain special null geodesics with the fixed radial coordinate (critical radius), along which the Penrose limit gives string theories with constant mass. We also study string theories with time-dependent mass, which arise from the Penrose limit of the brane backgrounds. We examine equations of motion of the strings in the asymptotic flat region and around the critical radius. In particular, for (p,q) fivebranes, we find that the string equatio…
We study dynamics of a cosmic string in a metastable brane configuration in Type IIA string theory. We first discuss a decay process of the cosmic string via a fuzzy brane (equivalently bubble/string bound state) by neglecting gravitational corrections in ten-dimension. We find that depending on the strength of the magnetic field induced on the bubble, the decay rate can be either larger or smaller than that of $O(4)$ symmetric bubble. Then, we investigate gravitational corrections to the fuzzy brane by using the extremal black $NS$-five brane solution, which makes the lifetime of the metastab…
It is well known that one-loop free energy of closed strings diverges above the Hagedorn temperature. One explanation for this divergence is that a `winding mode' in the Euclidean time direction becomes tachyonic above the Hagedorn temperature. The Hagedorn transition of closed strings has been proposed as a phase transition via condensation of this winding tachyon. However, we have not known the stable minimum of the potential of this winding tachyon so far. On the other hand, we have previously calculated the finite temperature effective potential of open strings on D-brane--anti-D-brane pai…
We probe the open fundamental strings in Dp-brane (p=1, 3, 5) backgrounds and find new classes of rotating and orbiting string solutions. We show that for various worldsheet embedding ansatz we get solutions of the string equations of motion that correspond to the well known giant magnon and single spikes, in addition to few new solutions corresponding to the orbiting strings. We make a systematic study of both rigidly rotating and orbiting strings in D1, D3 and D5-brane backgrounds.
We construct Dp-branes in bosonic string theory as unstable lumps in a truncated string field theory of open strings on a D25-brane. We find that the lowest level truncation gives good quantitative agreement with the predicted D-brane tension and low-lying spectrum of the D-brane for sufficiently large p and study the effect of the next level corrections for p=24. We show that a U(1) gauge field zero mode on the D-brane arises through a mechanism reminiscent of the Randall-Sundrum mechanism for gravity.
An sp-brane can be viewed as the creation and decay of an unstable D(p+1)-brane. It is argued that the decaying half of an sp-brane can be described by a variant of boundary Liouville theory. The pair creation of open strings by a decaying s-brane is studied in the minisuperspace approximation to the Liouville theory. In this approximation a Hagedorn-like divergence is found in the pair creation rate, suggesting the s-brane energy is rapidly transferred into closed string radiation.
We study various aspects of D-branes in the two families of closed N=2 strings denoted by αand βin hep-th/0211147. We consider two types of N=2 boundary conditions, A-type and B-type. We analyse the D-branes geometry. We compute open and closed string scattering amplitudes in the presence of the D-branes and discuss the results. We find that, except the space filling D-branes, the B-type D-branes decouple from the bulk. The A-type D-branes exhibit inconsistency. We construct the D-branes effective worldvolume theories. They are given by a dimensional reduction of self-dual Yang-Mills theory in…
The amplitudes for emission and scattering of N=2 strings off D-branes are calculated. We consider in detail the amplitudes <cc> and <occ> for the different types of D-branes. For some D-branes we find massive poles in the scattering spectrum that are absent in the ordinary N=2 spectrum.
We consider early time cosmic evolution in string gas cosmology dominated by open strings attached to D-branes. After reviewing statistical properties of open strings in D-brane backgrounds, we use dilaton-gravity equations to determine the string frame fields. Although, there are distinctions in the Hagedorn regime thermodynamics and dilaton coupling as compared to closed strings, it seems difficult to avoid Jeans instability and assume thermal equilibrium simultaneously, which is already a known problem for closed strings. We also examine characteristics of a possible subsequent large radius…
In this Ph.D. thesis, we study some aspects of strings and branes. We mainly focus on anomalous D-brane couplings and on non-supersymmetric branes. In Chapter 2, we illustrate three key concepts in a field theory context: duality, supersymmetry and anomaly inflow. Chapter 3 contains an introduction to string theory, emphasizing the concepts relevant to this thesis, like string scattering amplitudes and D-brane actions. In Chapter 4, we introduce the boundary state formalism and use it to check the presence of anomalous couplings in the D-brane Wess-Zumino action. In addition, we show that this…
We study the (p,q)5-brane dynamics from the viewpoint of Matrix string theory in the T-dualized ALE background. The most remarkable feature in the (p,q)5-brane is the existence of ``fractional string'', which appears as the instanton of 5-brane gauge theory. We approach to the physical aspects of fractional string by means of the two types of Matrix string probes: One of which is that given in hep-th/9710065. As the second probe we present the Matrix string theory describing the fractional string itself. We calculate the moduli space metrics in the respective cases and argue on the specific be…
We present two new solutions of Romans' massive type IIA supergravity characterized by the two non-trivial massive potentials of Romans' theory: the NSNS 2-form and the RR 7-form. They can be interpreted respectively as the intersection of a fundamental string and a D8-brane over a D0-brane and the intersection of a D6-brane with a D8-brane over a NSNS5-brane. The D8-brane manifests itself through the mass parameter and in the massless limit one recovers the standard fundamental string and D6-brane solutions. Although these solutions do not have the usual form for BPS bound states at threshold…
We study a matrix version of the purely cubic open string field theory as describing the expansion around the closed string vacuum. Any D-branes in the given closed string background can appear as classical solutions by using the identity projectors. Expansion around this solution gives the correct kinetic term for the open strings on the created D-branes while there are some subtleties in the unwanted degree of freedom.
We review two types of D-branes processes where open strings are created. In the first type, a closed string incident on a collection of D-branes is converted into a number of open strings running along them. For the case of threebranes we compare the leading absorption rate with that in semiclassical gravity, and find exact agreement. A supersymmetric non-renormalization theorem guarantees that this agreement survives all corrections in powers of the string coupling times the number of branes. The second type of process is creation of stretched open strings by crossing D-branes. We show that …
Dvali and Shifman have proposed a field-theoretic mechanism for localizing gauge fields to "branes" in higher dimensional spaces using confinement in a bulk gauge theory. The resulting objects have a number of qualitative features in common with string theory D-branes; they support a gauge field and flux strings can end on them. In this letter, we explore this analogy further, by considering what happens when N of these "branes" approach each other. Unlike in the case of D-branes, we find a reduction of the gauge symmetry as the "branes" overlap. This can be attributed to a tachyonic instabili…
We generalize the worldsheet derivation of the topological open/closed string duality given in hep-th/0205297 to cases when there are different types of D branes on the open string side. We use the mirror Landau-Ginzburg description to clarify the correspondence between D branes on the open string side and C phases on the closed string side. We also discuss the duality from the point of view of the B model.
String-bit models are both an efficient way of organizing string perturbation theory, and a possible non-perturbative composite description of string theory. This is a summary of ideas and results of string-bit and superstring-bit models, as presented in the Strings '96 conference.
Brane-like vertex operators play an important role in a worldsheet formulation of D-branes and M-theory. In this paper we derive the DBI D-brane action from NSR closed string sigma-model with brane-like states. We also show that these operators carry RR charges and define D-brane wavefunctions in a second quantized formalism.
