6,402 research outputs found

    Infra-red dynamics of D1-branes at the conifold

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    We study the infra-red dynamics of D1-branes at the conifold. We show using methods developed to study the infra-red dynamics of (4,4) theories, the infra-red degrees of freedom of the (2,2) theory of a single D1-brane at the conifold is that of a linear dilaton with background charge of 2\sqrt{2} and a compact scalar. The gauge theory of NN D1-branes at the conifold is used to formulate the matrix string in the conifold background.Comment: 20 pages, latex, some clarifications added, version to appear in JHE

    Excitations on wedge states and on the sliver

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    We study ghost number one excitations on the sliver to investigate the solution of string field actions around the tachyon vacuum. The generalized gluing and resmoothing theorem is used to develop a method for evaluating the effective action for excitations on both the wedge states and the sliver state. We analyze the discrete symmetries of the resulting effective action for excitations on the sliver. The gauge unfixed effective action till level two excitations on the sliver is evaluated. This is done for the case with the BRST operator c0c_0 and c0+(c2+c2)/2c_0 + (c_2 + c_{-2})/2 with excitations purely in the ghost sector. We find that the values of the effective potential at the local maximum lie close by for the zeroth and the second level of approximation. This indicates that level truncation in string field theory around the tachyon vacuum using excitations on the sliver converges for both choices of the BRST operator. It also provides evidence for the conjectured string field theory actions around the tachyon vacuum.Comment: 31 pages, 1 figure, refrences added, corrected some typo

    U(1) gauge invariance from open string field theory

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    The naive low energy effective action of the tachyon and the U(1) gauge field obtained from string field theory does not correspond to the world volume action of unstable branes in bosonic string theory. We show that there exists a field redefinition which relates the gauge field and the tachyon of the string field theory action to the fields in the world volume action of unstable branes. We identify a string gauge symmetry which corresponds to the U(1) gauge transformation. This is done to the first non-linear order in the fields. We examine the vector fluctuations at the tachyon condensate till level (4,8).Comment: Section on transverse photon at tachyon condensate added, 23 pages, Uses JHEP.cl

    Tachyon condensation in the D0/D4 system

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    The D0/D4 system with a Neveu-Schwarz B-field in the spatial directions of the D4-brane has a tachyon in the spectrum of the (0,4) strings. The tachyon signals the instability of the system to form a bound state of the D0-brane with the D4-brane. We use the Wess-Zumino-Witten like open superstring field theory formulated by Berkovits to study the tachyon potential for this system. The tachyon potential lies outside the universality class of the D-brane anti-D-brane system. It is a function of the B-field. We calculate the tachyon potential at the zeroth level approximation. The minimum of the tachyon potential in this case is expected to reproduce the mass defect involved in the formation of the D0/D4 bound state. We compare the minimum of the tachyon potential with the mass defect in three cases. For small values of the B-field we obtain 70% of the expected mass defect. For large values of the B-field with Pf(2παB)>0(2\pi\alpha' B) >0 the potential reduces to that of the D-brane anti-D-brane reproducing 62% of the expected mass defect. For large values of the B-field with Pf(2παB)<0(2\pi\alpha' B) <0 the minimum of the tachyon potential gives 25% of the expected mass defect. At the tachyon condensate we show that the (0,4) strings decouple from the low energy dynamics.Comment: 22 pages, 2 figures, uses JHEP.cl

    Anti-de Sitter gravity associated with the supergroup SU(1,12)×SU(1,12)SU(1,1|2)\times SU(1,1|2)

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    We construct the anti-de Sitter supergravity in three dimensions associated with the supergroup SU(1,12)×SU(1,12)SU(1,1|2)\times SU(1,1|2). The field content and the action are inferred using the fact that AdSAdS supergravity theories in three dimensions are Chern-Simons theories.Comment: 8 pages, no figures, LaTe

    Gravitational couplings in N=2{\cal N}=2 string compactifications and Mathieu Moonshine

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    We evaluate the low energy gravitational couplings, FgF_g in the heterotic E8×E8E_8\times E_8 string theory compactified on orbifolds of K3×T2K3\times T^2 by gg' which acts as a ZN\mathbb{Z}_N automorphisim on K3K3 together with a 1/N1/N shift along T2T^2. The orbifold gg' corresponds to the conjugacy classes of the Mathieu group M24M_{24}. The holomorphic piece of FgF_g is given in terms of a polylogarithim with index 32g3-2g and predicts the Gopakumar-Vafa invariants in the corresponding dual type II Calabi-Yau compactifications. We show that low lying Gopakumar-Vafa invariants for each of these compactifications including the twisted sectors are integers. We observe that the conifold singularity for all these compactifications occurs only when states in the twisted sectors become massless and the strength of the singularity is determined by the genus zero Gopakumar-Vafa invariant at this point in the moduli space.Comment: 54 pages, Mathematica code included in the source file, minor typos fixed, one reference adde

    Renyi entropies of free bosons on the torus and holography

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    We analytically evaluate the Renyi entropies for the two dimensional free boson CFT. The CFT is considered to be compactified on a circle and at finite temperature. The Renyi entropies S_n are evaluated for a single interval using the two point function of bosonic twist fields on a torus. For the case of the compact boson, the sum over the classical saddle points results in the Riemann-Siegel theta function associated with the A_{n-1} lattice. We then study the Renyi entropies in the decompactification regime. We show that in the limit when the size of the interval becomes the size of the spatial circle, the entanglement entropy reduces to the thermal entropy of free bosons on a circle. We then set up a systematic high temperature expansion of the Renyi entropies and evaluate the finite size corrections for free bosons. Finally we compare these finite size corrections both for the free boson CFT and the free fermion CFT with the one-loop corrections obtained from bulk three dimensional handlebody spacetimes which have higher genus Riemann surfaces as its boundary. One-loop corrections in these geometries are entirely determined by quantum numbers of the excitations present in the bulk. This implies that the leading finite size corrections contributions from one-loop determinants of the Chern-Simons gauge field and the Dirac field in the dual geometry should reproduce that of the free boson and the free fermion CFT respectively. By evaluating these corrections both in the bulk and in the CFT explicitly we show that this expectation is indeed true.Comment: Published version. 56 pages. 6 figures. Argument for the agreement of the leading finite size corrections evaluated from CFT and gravity has been adde

    Properties of dyons in N=4{\cal N}=4 theories at small charges

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    We study three properties of 1/41/4 BPS dyons at small charges in string compactifications which preserve N=4{\cal N}=4 supersymmetry. We evaluate the non-trivial constant present in the one loop statistical entropy for N=4{\cal N}=4 compactifications of type IIB theory on K3×T2K3\times T^2 orbifolded by an order ZN\mathbb{Z}_N freely acting orbifold gg' including all CHL compactifications. This constant is trivial for the un-orbifolded model but we show that it contributes crucially to the entropy of low charge dyons in all the orbifold models. We then show that the meromorphic Jacobi form which captures the degeneracy of 1/41/4 BPS states for the first two non-trivial magnetic charges can be decomposed into an Appell-Lerch sum and a mock Jacobi form transforming under Γ0(N)\Gamma_0(N). This generalizes the earlier observation of Dabholkar-Murthy-Zagier to the orbifold models. Finally we study the sign of the Fourier coefficients of the inverse Siegel modular form which counts the index of 1/41/4 BPS dyons in N=4{\cal N}=4 models obtained by freely acting Z2\mathbb{Z}_2 and Z3\mathbb{Z}_3 orbifolds of type II theory compactified on T6T^6. We show that sign of the index for sufficiently low charges and ensuring that it counts single centered black holes, violates the positivity conjecture of Sen which indicates that these states posses non-trivial hair

    Supersymmetry of classical solutions in Chern-Simons higher spin supergravity

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    We construct and study classical solutions in Chern-Simons supergravity based on the superalgebra sl(N|N-1). The algebra for the N=3 case is written down explicitly using the fact that it arises as the global part of the super conformal W_3 superalgebra. For this case we construct new classical solutions and study their supersymmetry. Using the algebra we write down the Killing spinor equations and explicitly construct the Killing spinor for conical defects and black holes in this theory. We show that for the general sl(N|N-1) theory the condition for the periodicity of the Killing spinor can be written in terms of the products of the odd roots of the super algebra and the eigenvalues of the holonomy matrix of the background. Thus the supersymmetry of a given background can be stated in terms of gauge invariant and well defined physical observables of the Chern-Simons theory. We then show that for N\geq 4, the sl(N|N-1) theory admits smooth supersymmetric conical defects.Comment: 40 pages, includes discussion of conical defects for N\geq 4, typos corrected and presentation improve
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