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Abstract We continue our analysis of open string field theory based on A ∞ -algebras obtained from Witten’s theory by attaching stubs to the elementary vertex. Classical solutions of the new theory can be obtained from known analytic solutions in Witten’s theory by applying a cohomomorphism. In a previous work two such cohomomorphisms were found, one non-cyclic, obtained from the homological perturbation lemma and another one by geometric methods. Here we show that to first order in the stub length the two resulting maps are related by a combination of a gauge transformation and a term vanishing on-shell. We also extend our construction to more general gauges and explicitly calculate the first few orders of the new A ∞ -algebra solutions in the sliver frame.

Abstract We consider non-critical heterotic strings compactified on S 1. For full rank theories, they are related to odd self-dual lattices and are structurally of the same form as the critical non-supersymmetric theories. For dimensions up to 14 the associated moduli spaces are Coxeter polytopes already studied by Vinberg and Kaplinskaya. In the heterotic string context, the Coxeter diagrams of these moduli spaces are related through transformations representing the process of dimension changing tachyon condensation of Hellerman-Swanson. For dimensions 8 and 6 respectively on S 1 and T 2 we show that at special points in the moduli space the subcritical string is the CHS background for two coincident NS5-branes and the intersection of two such pairs. These configurations are interpreted as an end result of condensing heterotic winding tachyons along one or two Scherck-Schwarz circles at self-dual radius. We give evidence that in the first case there is a T-duality between the pair of NS5-branes and a recently constructed non-supersymmetric heterotic 6-brane.

We derive an analog of Mirzakhani’s recursion relation for hyperbolic string vertices and investigate its implications for closed string field theory. Central to our construction are systolic volumes: the Weil-Petersson volumes of regions in moduli spaces of Riemann surfaces whose elements have systoles L ≥ 0. These volumes can be shown to satisfy a recursion relation through a modification of Mirzakhani’s recursion as long as L ≤ 2 sinh−1 1. Applying the pants decomposition of Riemann surfaces to off-shell string amplitudes, we promote this recursion to hyperbolic string field theory and demonstrate the higher order vertices are determined by the cubic vertex iteratively for any background. Such structure implies the solutions of closed string field theory obey a quadratic integral equation. We illustrate the utility of our approach in an example of a stubbed scalar theory.

Abstract In this paper, I construct a bouncing cosmology by considering the backreaction of the winding condensate on a 1+1 dimensional cosmological model with a periodic spatial coordinate. I based my work on previous results that considered the backreaction of the winding condensate on a 1+1 dimensional Euclidean black hole. This cosmological model is obtained as an analytic continuation of a Euclidean black hole. I solved the equations and obtained non-singular solutions at near-Hagedorn temperatures, both numerically and analytically. To remain within the weak coupling regime, it is necessary to connect two solutions; otherwise, the dilaton, which determines the string coupling, would grow quadratically. This connection is achieved through a smooth coordinate transformation, ensuring the model’s validity. As a result, the model becomes geodesically complete and non-singular. The connection is made at a time in which the curvature is small, thereby avoiding higher-order α ′ corrections.

Abstract We derive an analog of Mirzakhani’s recursion relation for hyperbolic string vertices and investigate its implications for closed string field theory. Central to our construction are systolic volumes: the Weil-Petersson volumes of regions in moduli spaces of Riemann surfaces whose elements have systoles L ≥ 0. These volumes can be shown to satisfy a recursion relation through a modification of Mirzakhani’s recursion as long as L ≤ 2 sinh−1 1. Applying the pants decomposition of Riemann surfaces to off-shell string amplitudes, we promote this recursion to hyperbolic string field theory and demonstrate the higher order vertices are determined by the cubic vertex iteratively for any background. Such structure implies the solutions of closed string field theory obey a quadratic integral equation. We illustrate the utility of our approach in an example of a stubbed scalar theory.

In this paper, I construct a bouncing cosmology by considering the backreaction of the winding condensate on a 1+1 dimensional cosmological model with a periodic spatial coordinate. I based my work on previous results that considered the backreaction of the winding condensate on a 1+1 dimensional Euclidean black hole. This cosmological model is obtained as an analytic continuation of a Euclidean black hole. I solved the equations and obtained non-singular solutions at near-Hagedorn temperatures, both numerically and analytically. To remain within the weak coupling regime, it is necessary to connect two solutions; otherwise, the dilaton, which determines the string coupling, would grow quadratically. This connection is achieved through a smooth coordinate transformation, ensuring the model’s validity. As a result, the model becomes geodesically complete and non-singular. The connection is made at a time in which the curvature is small, thereby avoiding higher-order α′ corrections. [ABSTRACT FROM AUTHOR]

Abstract In the context of the black hole/string transition, it is useful to produce Euclidean string backgrounds representing hot and self-gravitating strings. We utilise analytical and numerical methods to find a smooth, stationary rotating solution in the heterotic string theory at high temperatures. The solution describes a spinning winding-momentum condensate living in three non-compact dimensions, and its backreaction on the thermal cycle. At low temperatures, we expect a transition between our solution to an analytical continuation of an axionic Kerr black hole.

We show generically that the dynamics of a probe particle near the event horizon of a non-extreme black hole is described by the tachyon effective action. The Hagedorn temperature in the action is always equal to the Hawking temperature of the background black hole. The fact suggests that the infalling particle should decay completely into gravitons or closed strings approaching the event horizon. The increased area in the black hole due to absorption of a particle should be interpreted as the entropy of degenerate states of the closed strings that the particle decays into. With the energy match condition between the infalling particle and the emitted closed strings on the event horizon, we examine this variational area-entropy relation and find that it matches in all cases if the closed string emission process from an unstable D0-brane obeys the first law. [ABSTRACT FROM AUTHOR]

In the context of the black hole/string transition, it is useful to produce Euclidean string backgrounds representing hot and self-gravitating strings. We utilise analytical and numerical methods to find a smooth, stationary rotating solution in the heterotic string theory at high temperatures. The solution describes a spinning winding-momentum condensate living in three non-compact dimensions, and its backreaction on the thermal cycle. At low temperatures, we expect a transition between our solution to an analytical continuation of an axionic Kerr black hole. [ABSTRACT FROM AUTHOR]

Abstract We define and compute the leading sphere diagram contribution to the entropy of the BTZ black hole supported by Kalb-Ramond flux in bosonic string theory. In a winding condensate description, integrating exactly over the constant mode for the radial direction of AdS3 reduces the problem to one of the correlation functions of winding operators in the free theory. The volume of the residual PSL(2,ℂ) gauge group of the sphere is canceled by the action of conformal transformations on the winding interaction insertions. We formulate a precise version of the replica trick in terms of (infinitesimally) non-integer winding condensates to produce the entropy of the BTZ black hole. The resulting entropy can be calculated from the one-point function of a non-local operator on the worldsheet.

Abstract We conjecture a two-dimensional conformal field theory built out of a linear dilaton and a compact βγ system deformed by winding condensates on each of the compact cycles. In particular, explicit expressions of the residues of the correlation functions are provided. As a worldsheet theory, it describes a stringy black hole in AdS3 (supported by the Kalb-Ramond flux) at the Hawking-Page temperature. It is expected to be connected to the Horowitz-Polchinski-like solution near the Hagedorn temperature of thermal AdS3 and Euclidean BTZ blackhole as we vary the temperature.

We conjecture a two-dimensional conformal field theory built out of a linear dilaton and a compact βγ system deformed by winding condensates on each of the compact cycles. In particular, explicit expressions of the residues of the correlation functions are provided. As a worldsheet theory, it describes a stringy black hole in AdS3 (supported by the Kalb-Ramond flux) at the Hawking-Page temperature. It is expected to be connected to the Horowitz-Polchinski-like solution near the Hagedorn temperature of thermal AdS3 and Euclidean BTZ blackhole as we vary the temperature. [ABSTRACT FROM AUTHOR]

We define and compute the leading sphere diagram contribution to the entropy of the BTZ black hole supported by Kalb-Ramond flux in bosonic string theory. In a winding condensate description, integrating exactly over the constant mode for the radial direction of AdS3 reduces the problem to one of the correlation functions of winding operators in the free theory. The volume of the residual PSL(2,ℂ) gauge group of the sphere is canceled by the action of conformal transformations on the winding interaction insertions. We formulate a precise version of the replica trick in terms of (infinitesimally) non-integer winding condensates to produce the entropy of the BTZ black hole. The resulting entropy can be calculated from the one-point function of a non-local operator on the worldsheet. [ABSTRACT FROM AUTHOR]

Abstract We investigate Wilsonian effective field theory as a model for the construction of the tachyon potential and nonperturbative vacua in closed string field theory. In a number of cases we are able to find the effective potential exactly, and observe what appear to be universal features. We find that the effective field theory contains the same nonperturbative vacuum structure as the bare Lagrangian, though this information is encoded less efficiently as the distance scale of the effective field theory is increased. The implication is that closed string field theory plausibly contains information about the nonperturbative vacuum structure of string theory, in spite of its similarities to effective field theory. We also truncate the effective potential at a fixed power of the field and investigate how the global structure of the effective potential may be approximated via Padé resummation. Qualitative comparisons suggest that computation of the eighth to sixteenth order closed string vertex should be enough to obtain reliable results for the closed string field theory action evaluated on the tachyon field.

Abstract Combining previous results, the D3- D ¯ 3 $$ \overline{D}3 $$ -brane pair potential U(T, ϕ) is presented here, where the inflaton ϕ measures the separation between the D3-brane and the anti-D3-brane, and the complex scalar mode T becomes tachyonic when the annihilation of the branes happens as they collide. Besides the distinct form of the inflationary potential, this hybrid inflationary model differs from a typical hybrid model in 2 important aspects: (1) U(T, ϕ) becomes complex when T becomes tachyonic, where Im U(T, ϕ) plays an important role in the dynamics towards the end of the inflationary epoch; (2) tunnelling during the inflationary epoch can happen; this is particularly relevant if there are multiple D3- D ¯ 3 $$ \overline{D}3 $$ -brane pairs in different warped throats. Besides the production of cosmic superstrings, the model offers the possibility of first order phase transition that may generate large enough density perturbation for the primordial black hole production. Stochastic gravitational wave background from these sources remain to be fully investigated.

We investigate Wilsonian effective field theory as a model for the construction of the tachyon potential and nonperturbative vacua in closed string field theory. In a number of cases we are able to find the effective potential exactly, and observe what appear to be universal features. We find that the effective field theory contains the same nonperturbative vacuum structure as the bare Lagrangian, though this information is encoded less efficiently as the distance scale of the effective field theory is increased. The implication is that closed string field theory plausibly contains information about the nonperturbative vacuum structure of string theory, in spite of its similarities to effective field theory. We also truncate the effective potential at a fixed power of the field and investigate how the global structure of the effective potential may be approximated via Padé resummation. Qualitative comparisons suggest that computation of the eighth to sixteenth order closed string vertex should be enough to obtain reliable results for the closed string field theory action evaluated on the tachyon field. [ABSTRACT FROM AUTHOR]

In this short note, we present analysis of the tachyon kink solution on the world-volume of unstable Dp-brane in general background as the solution of the Hamiltonian equations of motion. We also find Hamiltonian for simplified system of Dp-brane and anti-Dp-brane and study its properties. [ABSTRACT FROM AUTHOR]

Abstract There are various reasons why adding stubs to the vertices of open string field theory (OSFT) is interesting: the stubs can not only tame certain singularities and make the theory more well-behaved, but also the new theory shares a lot of similarities with closed string field theory, which helps to improve our understanding of its structure and possible solutions. In this paper we explore two natural ways of implementing stubs into the framework of OSFT, resulting in an A ∞ -algebra giving rise to infinitely many vertices. We find two distinct consistent actions, both generated by a field redefinition, interestingly sharing the same equations of motion. In the last section we illustrate their relationship and physical meaning by applying our construction to nearly marginal solutions.

Abstract We analyze boundary states in the SU(2) k WZW model using open string field theory in the level truncation approximation. We develop algorithms that allow effective calculation of the action in this model and we search for classical solutions of the equations of motion, which are conjectured to describe boundary states. We find three types of solutions. First, there are real solutions that represent maximally symmetric Cardy boundary states and we show that they satisfy certain selection rules regarding their parameters. Next, we find complex solutions that go beyond the SU(2) model and describe maximally symmetric SL(2, ℂ) boundary conditions. Finally, we find exotic solutions that correspond to symmetry-breaking boundary states. Most of real exotic solutions describe the so-called B-brane boundary states, but some may represent yet unknown boundary states.

Abstract In this work, we propose a string-inspired two fields inflation model to address the fine-tuning problem that the standard inflation model suffers. The fast-rolling tachyon T $$ \mathcal{T} $$ originated from the D-brane and anti-D-brane pair annihilation locks the inflaton φ slowly rolling on a Higgs-like potential V φ = − m φ 2 φ 2 + λ φ 4 $$ V\left(\varphi \right)=-{m}_{\varphi}^2{\varphi}^2+\lambda {\varphi}^4 $$ and drives a kinetically stabilized (KS) inflation. Our numerical simulation confirms such a solution is a dynamic attractor. In particular, for λ < 0.8 × 10 −3, the e-folding number contributed by the KS inflation phase can be larger than 62 to solve the horizon and flatness problems of Big Bang theory. Notably, this KS inflation generates a nearly scale-invariant primordial curvature perturbations spectrum consistent with current cosmic microwave background (CMB) observations. It predicts a low tensor-to-scalar ratio, which the current primordial gravitational wave background (the B-modes in CMB) searches favor.

There are various reasons why adding stubs to the vertices of open string field theory (OSFT) is interesting: the stubs can not only tame certain singularities and make the theory more well-behaved, but also the new theory shares a lot of similarities with closed string field theory, which helps to improve our understanding of its structure and possible solutions. In this paper we explore two natural ways of implementing stubs into the framework of OSFT, resulting in an A∞-algebra giving rise to infinitely many vertices. We find two distinct consistent actions, both generated by a field redefinition, interestingly sharing the same equations of motion. In the last section we illustrate their relationship and physical meaning by applying our construction to nearly marginal solutions. [ABSTRACT FROM AUTHOR]

Abstract We show that the entropy of strings that wind around the Euclidean time circle is proportional to the Noether charge associated with translations along the T-dual time direction. We consider an effective target-space field theory which includes a large class of terms in the action with various modes, interactions and α′ corrections. The entropy and the Noether charge are shown to depend only on the values of fields at the boundary of space. The classical entropy, which is proportional to the inverse of Newton’s constant, is then calculated by evaluating the appropriate boundary term for various geometries with and without a horizon. We verify, in our framework, that for higher-curvature pure gravity theories, the Wald entropy of static neutral black hole solutions is equal to the entropy derived from the Gibbons-Hawking boundary term. We then proceed to discuss horizonless geometries which contain, due to the back-reaction of the strings and branes, a second boundary in addition to the asymptotic boundary. Near this “punctured” boundary, the time-time component of the metric and the derivatives of its logarithm approach zero. Assuming that there are such non-singular solutions, we identify the entropy of the strings and branes in this geometry with the entropy of the solution to all orders in α′. If the asymptotic region of an α′-corrected neutral black hole is connected through the bulk to a puncture, then the black hole entropy is equal to the entropy of the strings and branes. Later, we discuss configurations similar to the charged black p-brane solutions of Horowitz and Strominger, with the second boundary, and show that, to leading order in the α′ expansion, the classical entropy of the strings and branes is equal exactly to the Bekenstein-Hawking entropy. This result is extended to a configuration that asymptotes to AdS.

Abstract Using the dilaton theorem, we show that the classical action of closed string field theory vanishes on-shell.

Abstract We consider deformations of D-brane systems induced by a change in the closed string background in the framework of bosonic open-closed string field theory, where it is possible to unambiguously tame infrared divergences originating from both open and closed string degenerations. A closed string classical solution induces a tadpole for the open strings which shifts the open string vacuum and generates a cosmological constant composed of two terms: one which is directly related to the closed string solution and the other which depends on the open string vacuum shift. We show that only the sum of these two terms is invariant under closed SFT gauge transformations and therefore is an observable. We conjecture that this observable is universally proportional to the shift in the world-sheet disk partition function between the starting D-brane in undeformed background and the final D-brane in deformed background, which typically includes also a change in the string coupling constant. We test the conjecture by considering a perturbative closed string solution describing deformations of a Narain compactification and, from the SFT cosmological constant, we reproduce the expected shift in the g-function of various D-branes living in the compactification. In doing this we are also able to identify a surprising change in the string coupling constant at second order in the deformation.

We analyze boundary states in the SU(2)k WZW model using open string field theory in the level truncation approximation. We develop algorithms that allow effective calculation of the action in this model and we search for classical solutions of the equations of motion, which are conjectured to describe boundary states. We find three types of solutions. First, there are real solutions that represent maximally symmetric Cardy boundary states and we show that they satisfy certain selection rules regarding their parameters. Next, we find complex solutions that go beyond the SU(2) model and describe maximally symmetric SL(2, ℂ) boundary conditions. Finally, we find exotic solutions that correspond to symmetry-breaking boundary states. Most of real exotic solutions describe the so-called B-brane boundary states, but some may represent yet unknown boundary states. [ABSTRACT FROM AUTHOR]

Abstract This paper is devoted to the construction of stable and unstable Dp-branes in generalized Carroll space-times. We also study tachyon solutions on the world-volume of unstable Dp-brane in Carrollian background and discuss their physical interpretations.

Abstract We describe timelike linear dilaton backgrounds of supercritical string theories as time-dependent Dynamical Cobordisms in string theory, with their spacelike singularity as a boundary defining the beginning of time. We propose and provide compelling evidence that its microscopic interpretation corresponds to a region of (a strong coupling version of) closed tachyon condensation. We argue that this beginning of time is closely related to (and shares the same scaling behaviour as) the bubbles of nothing obtained in a weakly coupled background with lightlike tachyon condensation. As an intermediate result, we also provide the description of the latter as lightlike Dynamical Cobordism.

We propose an action for the D0-brane anti-D0-brane system that has its exact solution corresponding to the marginal tachyon profile defined for arbitrary constant separation of these D-branes. We also find its covariant formulation and generalization to higher dimensional Dp-branes. [ABSTRACT FROM AUTHOR]

In this work, we propose a string-inspired two fields inflation model to address the fine-tuning problem that the standard inflation model suffers. The fast-rolling tachyon T originated from the D-brane and anti-D-brane pair annihilation locks the inflaton φ slowly rolling on a Higgs-like potential V φ = − m φ 2 φ 2 + λ φ 4 and drives a kinetically stabilized (KS) inflation. Our numerical simulation confirms such a solution is a dynamic attractor. In particular, for λ < 0.8 × 10−3, the e-folding number contributed by the KS inflation phase can be larger than 62 to solve the horizon and flatness problems of Big Bang theory. Notably, this KS inflation generates a nearly scale-invariant primordial curvature perturbations spectrum consistent with current cosmic microwave background (CMB) observations. It predicts a low tensor-to-scalar ratio, which the current primordial gravitational wave background (the B-modes in CMB) searches favor. [ABSTRACT FROM AUTHOR]

Abstract We consider a nonlocal scalar field theory inspired by the tachyon action in open string field theory. The Lorentz-covariant action is characterized by a parameter ξ 2 that quantifies the amount of nonlocality. Restricting to purely time-dependent configurations, we show that a field redefinition perturbative in ξ 2 reduces the action to a local two-derivative theory with a ξ 2-dependent potential. This picture is supported by evidence that the redefinition maps the wildly oscillating rolling tachyon solutions of the nonlocal theory to conventional rolling in the new scalar potential. For general field configurations we exhibit an obstruction to a local Lorentz-covariant formulation, but we can still achieve a formulation local in time, as well as a light-cone formulation. These constructions provide an initial value formulation and a Hamiltonian. Their causality is consistent with a lack of superluminal behavior in the nonlocal theory.

The following notes derive from review lectures on the subject of analytic solutions in open string field theory, given at the School for String Field Theory and String Phenomenology at the Harish-Chandra Research Institute in February 2018. [ABSTRACT FROM AUTHOR]

We show that the entropy of strings that wind around the Euclidean time circle is proportional to the Noether charge associated with translations along the T-dual time direction. We consider an effective target-space field theory which includes a large class of terms in the action with various modes, interactions and α′ corrections. The entropy and the Noether charge are shown to depend only on the values of fields at the boundary of space. The classical entropy, which is proportional to the inverse of Newton’s constant, is then calculated by evaluating the appropriate boundary term for various geometries with and without a horizon. We verify, in our framework, that for higher-curvature pure gravity theories, the Wald entropy of static neutral black hole solutions is equal to the entropy derived from the Gibbons-Hawking boundary term. We then proceed to discuss horizonless geometries which contain, due to the back-reaction of the strings and branes, a second boundary in addition to the asymptotic boundary. Near this “punctured” boundary, the time-time component of the metric and the derivatives of its logarithm approach zero. Assuming that there are such non-singular solutions, we identify the entropy of the strings and branes in this geometry with the entropy of the solution to all orders in α′. If the asymptotic region of an α′-corrected neutral black hole is connected through the bulk to a puncture, then the black hole entropy is equal to the entropy of the strings and branes. Later, we discuss configurations similar to the charged black p-brane solutions of Horowitz and Strominger, with the second boundary, and show that, to leading order in the α′ expansion, the classical entropy of the strings and branes is equal exactly to the Bekenstein-Hawking entropy. This result is extended to a configuration that asymptotes to AdS. [ABSTRACT FROM AUTHOR]

Using the dilaton theorem, we show that the classical action of closed string field theory vanishes on-shell. [ABSTRACT FROM AUTHOR]

We consider deformations of D-brane systems induced by a change in the closed string background in the framework of bosonic open-closed string field theory, where it is possible to unambiguously tame infrared divergences originating from both open and closed string degenerations. A closed string classical solution induces a tadpole for the open strings which shifts the open string vacuum and generates a cosmological constant composed of two terms: one which is directly related to the closed string solution and the other which depends on the open string vacuum shift. We show that only the sum of these two terms is invariant under closed SFT gauge transformations and therefore is an observable. We conjecture that this observable is universally proportional to the shift in the world-sheet disk partition function between the starting D-brane in undeformed background and the final D-brane in deformed background, which typically includes also a change in the string coupling constant. We test the conjecture by considering a perturbative closed string solution describing deformations of a Narain compactification and, from the SFT cosmological constant, we reproduce the expected shift in the g-function of various D-branes living in the compactification. In doing this we are also able to identify a surprising change in the string coupling constant at second order in the deformation. [ABSTRACT FROM AUTHOR]

Abstract We calculate the entropy of an asymptotically Schwarzschild black hole, using an effective field theory of winding modes in type II string theory. In Euclidean signature, the geometry of the black hole contains a thermal cycle which shrinks towards the horizon. The light excitations thus include, in addition to the metric and the dilaton, also the winding modes around this cycle. The winding modes condense in the near-horizon region and source the geometry of the thermal cycle. Using the effective field theory action and standard thermodynamic relations, we show that the entropy, which is also sourced by the winding modes condensate, is exactly equal to the Bekenstein-Hawking entropy of the black hole. We then discuss some properties of the winding mode condensate and end with an application of our method to an asymptotically linear-dilaton black hole.

Abstract We propose a new way to compute the genus zero Gopakumar-Vafa invariants for two families of non-toric non-compact Calabi-Yau threefolds that admit simple flops: Reid’s Pagodas, and Laufer’s examples. We exploit the duality between M-theory on these threefolds, and IIA string theory with D6-branes and O6-planes. From this perspective, the GV invariants are detected as five-dimensional open string zero modes. We propose a definition for genus zero GV invariants for threefolds that do not admit small crepant resolutions. We find that in most cases, non-geometric T-brane data is required in order to fully specify the invariants.

Abstract The open string field theory of Witten (SFT) has a close formal similarity with Chern-Simons theory in three dimensions. This similarity is due to the fact that the former theory has concepts corresponding to forms, exterior derivative, wedge product and integration over the manifold. In this paper, we introduce the interior product and the Lie derivative in the KBc subsector of SFT. The interior product in SFT is specified by a two-component “tangent vector” and lowers the ghost number by one (like the ordinary interior product maps a p-form to (p − 1)-form). The Lie derivative in SFT is defined as the anti-commutator of the interior product and the BRST operator. The important property of these two operations is that they respect the KBc algebra. Deforming the original (K, B, c) by using the Lie derivative, we can consider an infinite copies of the KBc algebra, which we call the KBc manifold. As an application, we construct the Wilson line on the manifold, which could play a role in reproducing degenerate fluctuation modes around a multi-brane solution.

Abstract We discuss interacting, closed, bosonic and superstrings in thermal equilibrium at temperatures close to the Hagedorn temperature in flat space. We calculate S-matrix elements of the strings at the Hagedorn temperature and use them to construct a low-energy effective action for interacting strings near the Hagedorn temperature. We show, in particular, that the four-point amplitude of massless winding modes leads to a positive quartic interaction. Furthermore, the effective field theory has a generalized conformal structure, namely, it is conformally invariant when the temperature is assigned an appropriate scaling dimension. Then, we show that the equations of motion resulting from the effective action possess a winding-mode-condensate background solution above the Hagedorn temperature and present a worldsheet conformal field theory, similar to a Sine-Gordon theory, that corresponds to this solution. We find that the Hagedorn phase transition in our setup is second order, in contrast to a first-order transition that was found previously in different setups.

Abstract Superstring/M-theory compactified on compact Ricci flat manifolds have recently been conjectured to exhibit instabilities whenever the metrics do not have special holonomy. We use worldsheet conformal field theory to investigate instabilities of Type II superstring theories on compact, Ricci flat, spin 3-manifolds including a worldsheet description of their spin structures. The instabilities are signalled by the appearance of stringy tachyons at small radius and a negative (1-loop) vacuum energy density at large radius. We briefly discuss the extension to higher dimensions.

Abstract Intersecting D-brane models and their T-dual magnetic compactifications provide an attractive framework for particle physics, allowing for chiral fermions and supersymmetry breaking. Generically, magnetic compactifications have tachyons that are usually removed by Wilson lines. However, quantum corrections prevent local minima for Wilson lines. We therefore study tachyon condensation in the simplest case, the magnetic compactification of type I string theory on a torus to eight dimensions. We find that tachyon condensation restores supersymmetry, which is broken by the magnetic flux, and we compute the Kaluza-Klein mass spectrum. The gauge group SO(32) is broken to USp(16). We give arguments that the vacuum reached by tachyon condensation corresponds to the unique 8d superstring theory already known in the literature, with discrete B ab background or, in the T-dual version, the type IIB orientifold with three O7 − -planes, one O7+-plane and eight D7-branes coincident with the O7+-plane. The ground state after tachyon condensation is supersymmetric and has no chiral fermions.

Abstract We investigate the effect of a non-zero magnetic field on the chiral condensate using a holographic QCD approach. We extend the model proposed by Iatrakis, Kiritsis and Paredes in [1] that realises chiral symmetry breaking dynamically from 5d tachyon condensation. We calculate the chiral condensate, magnetisation and susceptibilities for the confined and deconfined phases. The model leads, in the probe approximation, to magnetic catalysis of chiral symmetry breaking in both confined and deconfined phases. In the chiral limit, m q = 0, we find that in the deconfined phase a sufficiently strong magnetic field leads to a second order phase transition from the chirally restored phase to a chirally broken phase. The transition becomes a crossover as the quark mass increases. Due to a scaling in the temperature, the chiral transition will also be interpreted as a transition in the temperature for fixed magnetic field. We elaborate on the relationship between the chiral condensate, magnetisation and the (magnetic) free energy density. We compare our results at low and moderate temperatures with lattice QCD results.

Abstract This paper is devoted to the construction of unstable D-brane action in torsional Newton-Cartan background through T-duality along null direction. We determine corresponding equations of motion and analyze their solution that corresponds to lower dimensional non-relativistic D(p-1)-brane. We also find Hamiltonian for unstable Dp-brane and study tachyon vacuum solutions that can be interpreted as gas of non-relativistic strings.

Abstract In a linear dilaton background, it has been argued that an unstable D-brane can decay to the tachyon vacuum without leaving behind a remnant of tachyon matter. Here we address the question of how the D-brane can decay to the tachyon vacuum when the tachyon vacuum does not support physical fluctuations. Using the formalism of open string field theory, we find that the tachyon vacuum can support fluctuations provided they are “hidden” as nonperturbative effects behind a pure gauge asymptotic series.

We calculate the entropy of an asymptotically Schwarzschild black hole, using an effective field theory of winding modes in type II string theory. In Euclidean signature, the geometry of the black hole contains a thermal cycle which shrinks towards the horizon. The light excitations thus include, in addition to the metric and the dilaton, also the winding modes around this cycle. The winding modes condense in the near-horizon region and source the geometry of the thermal cycle. Using the effective field theory action and standard thermodynamic relations, we show that the entropy, which is also sourced by the winding modes condensate, is exactly equal to the Bekenstein-Hawking entropy of the black hole. We then discuss some properties of the winding mode condensate and end with an application of our method to an asymptotically linear-dilaton black hole. [ABSTRACT FROM AUTHOR]

Abstract Based on the level truncation scheme, we develop a new numerical method to evaluate the tachyon vacuum solution in the Schnabl gauge up to level L = 24. We confirm the prediction that the energy associated to this numerical solution has a local minimum at level L = 12. Extrapolating the energy data of L ≤ 24 to infinite level, we observe that the energy goes towards the analytical value −1, nevertheless the precision of the extrapolation is lower than in the Siegel gauge. Furthermore, we analyze the Ellwood invariant and show that its value converges monotonically towards the expected analytical result. We also study the tachyon vacuum expectation value (vev) and some other coefficients of the solution. Finally, some consistency checks of the solution are performed, and we briefly discuss the search for other Schnabl gauge numerical solutions.

Abstract We explore Carroll limit corresponding to M2 as well as M3 branes propagating over 11D supergravity backgrounds in M theory. In the first part of the analysis, we introduce the membrane Carroll limit associated to M2 branes propagating over M theory supergravity backgrounds. Considering two specific M2 brane embeddings, we further outline the solutions corresponding to the Hamilton’s dynamical equations in the Carroll limit. We further consider the so called stringy Carroll limit associated to M2 branes and outline the corresponding solutions to the underlying Hamilton’s equations of motion by considering specific M2 brane embeddings over 11D target space geometry. As a further illustration of our analysis, considering the Nambu-Goto action, we show the equivalence between different world-volume descriptions in the Carroll limit of M2 branes. Finally, considering the stringy Carroll limit, we explore the constraint structure as well as the Hamiltonian dynamics associated to unstable M3 branes in 11D supergravity and obtain the corresponding effective world-volume description around their respective tachyon vacua.

Abstract We consider phase transitions occurring in four-dimensional heterotic orbifold models, when the scale of spontaneous breaking of N $$ \mathcal{N} $$ = 1 supersymmetry is of the order of the string scale. The super-Higgs mechanism is implemented by imposing distinct boundary conditions for bosons and fermions along an internal circle of radius R. Depending on the orbifold action, the usual scalars becoming tachyonic when R falls below the Hagedorn radius may or may not be projected out of the spectrum. In all cases, infinitely many other scalars, which are pure Kaluza-Klein or pure winding states along other internal directions, become tachyonic in subregions in moduli space. We derive the off-shell tree level effective potential that takes into account these potentially tachyonic modes. We show that when a combination of the usual tachyons survives the orbifold action, it is the only degree of freedom that actually condenses.

Abstract Motivated by the appearance of associativity anomalies in the context of superstring field theory, we give a generalized solution built from boundary condition changing operators which can be associated to a generic tachyon vacuum in the KBc subalgebra of the Okawa form. We articulate sufficient conditions on the choice of tachyon vacuum to ensure that ambiguous products do not appear in the equations of motion.

We propose a new way to compute the genus zero Gopakumar-Vafa invariants for two families of non-toric non-compact Calabi-Yau threefolds that admit simple flops: Reid's Pagodas, and Laufer's examples. We exploit the duality between M-theory on these threefolds, and IIA string theory with D6-branes and O6-planes. From this perspective, the GV invariants are detected as five-dimensional open string zero modes. We propose a definition for genus zero GV invariants for threefolds that do not admit small crepant resolutions. We find that in most cases, non-geometric T-brane data is required in order to fully specify the invariants. [ABSTRACT FROM AUTHOR]