String Creation, D-branes and Effective Field Theory

This paper addresses several unsettled issues associated with string creation in systems of orthogonal Dp-D(8-p) branes. The interaction between the branes can be understood either from the closed string or open string picture. In the closed string picture it has been noted that the DBI action fails to capture an extra RR exchange between the branes. We demonstrate how this problem persists upon lifting to M-theory. These D-brane systems are analysed in the closed string picture by using gauge-fixed boundary states in a non-standard lightcone gauge, in which RR exchange can be analysed precisely. The missing piece in the DBI action also manifests itself in the open string picture as a mismatch between the Coleman-Weinberg potential obtained from the effective field theory and the corresponding open string calculation. We show that this difference can be reconciled by taking into account the superghosts in the (0+1)effective theory of the chiral fermion, that arises from gauge fixing the spontaneously broken world-line local supersymmetries.Comment: 33 page

A model for the synthesis of naturally occurring benzisochromenequinones

1,3-Dimethylbenzisochromene-5,10-quinone 14 is obtained in good yield when 2-(1′-hydroxyethyl)-3-prop-2″-enyl-1,4-naphthoquinone 13 is treated briefly with bisacetonitriledichloropalladium(II) in solution in dichloromethane at room temperature

String Pair Creations in D-brane Systems

We investigate the criterion, on the Born-Infeld background fields, for the open string pair creation to occur in D$p$-(anti-)D$p$-brane systems. Although the pair creation occurs generically in both D$p$-D$p$ and D$p$-anti-D$p$ systems for the cases which meet the criterion, it is more drastic in D$p$-anti-D$p$-brane systems by some exponential factor depending on the background fields. Various configurations exhibiting pair creations are obtained via duality transformations. These include the spacelike scissors and two D-strings (slanted at different angles) passing through each other. We raise the scissors paradox and suggest a resolution based on the triple junction in IIB setup.Comment: V2. 1+28 pages, 5 figures in JHEP3, minor changes, added reference

Gravitational couplings of orientifold planes

We reanalyse the gravitational couplings of the perturbative orientifold planes $Op^-$, $Op^+$ (and D-branes). We first compute their $D_{-1}$ instantonic corrections for $p=3$. Then, by using U-dualities, we obtain the Wess-Zumino terms of orientifolds with RR flux for $p \leq 5$. The expressions for the effective actions can be partially checked via M-theory. We point out a previous oversimplification and we show in fact that the difficulty still stands in the way of the full computation of 7 Brane instanton corrections.Comment: 13 pages, 1 figure, 2 tables. 3 references adde

The Pole Part of the 1PI Four-Point Function in Light-Cone Gauge Yang-Mills Theory

The complete UV-divergent contribution to the one-loop 1PI four-point function of Yang-Mills theory in the light-cone gauge is computed in this paper. The formidable UV-divergent contributions arising from each four-point Feynman diagram yield a succinct final result which contains nonlocal terms as expected. These nonlocal contributions are consistent with gauge symmetry, and correspond to a nonlocal renormalization of the wave function. Renormalization of Yang-Mills theory in the light-cone gauge is thus shown explicitly at the one-loop level.Comment: 35 pages, 18 figures. To be published in Nuc. Phys.

SUSY Breaking and Moduli Stabilization from Fluxes in Gauged 6D Supergravity

We construct the 4D N=1 supergravity which describes the low-energy limit of 6D supergravity compactified on a sphere with a monopole background a la Salam and Sezgin. This provides a simple setting sharing the main properties of realistic string compactifications such as flat 4D spacetime, chiral fermions and N=1 supersymmetry as well as Fayet-Iliopoulos terms induced by the Green-Schwarz mechanism. The matter content of the resulting theory is a supersymmetric SO(3)xU(1) gauge model with two chiral multiplets, S and T. The expectation value of T is fixed by the classical potential, and S describes a flat direction to all orders in perturbation theory. We consider possible perturbative corrections to the Kahler potential in inverse powers of $Re S$ and $Re T$, and find that under certain circumstances, and when taken together with low-energy gaugino condensation, these can lift the degeneracy of the flat direction for $Re S$. The resulting vacuum breaks supersymmetry at moderately low energies in comparison with the compactification scale, with positive cosmological constant. It is argued that the 6D model might itself be obtained from string compactifications, giving rise to realistic string compactifications on non Ricci flat manifolds. Possible phenomenological and cosmological applications are briefly discussed.Comment: 32 pages, 2 figures. Uses JHEP3.cls. References fixed and updated, some minor typos fixed. Corrected minor error concerning Kaluza-Klein scales. Results remain unchange

Inflation on an Open Racetrack

We present a variant of warped D-brane inflation by incorporating multiple sets of holomorphically-embedded D7-branes involved in moduli stabilization with extent into a warped throat. The resultant D3-brane motion depends on the D7-brane configuration and the relative position of the D3-brane in these backgrounds. The non-perturbative moduli stabilization superpotential takes the racetrack form, but the additional D3-brane open string moduli dependence provides more flexibilities in model building. For concreteness, we consider D3-brane motion in the warped deformed conifold with the presence of multiple D7-branes, and derive the scalar potential valid for the entire throat. By explicit tuning of the microphysical parameters, we obtain inflationary trajectories near an inflection point for various D7-brane configurations. Moreover, the open racetrack potential admits approximate Minkowski vacua before uplifting. We demonstrate with a concrete D-brane inflation model where the Hubble scale during inflation can exceed the gravitino mass. Finally, the multiple sets of D7-branes present in this open racetrack setup also provides a mechanism to stabilize the D3-brane to metastable vacua in the intermediate region of the warped throat.Comment: 29 pages, 15 figures, pre-print number and references adde

M-flation: Inflation From Matrix Valued Scalar Fields

We propose an inflationary scenario, M-flation, in which inflation is driven by three $N\times N$ hermitian matrices $\Phi_i, i=1,2,3$. The inflation potential of our model, which is strongly motivated from string theory, is constructed from $\Phi_{i}$ and their commutators. We show that one can consistently restrict the classical dynamics to a sector in which the $\Phi_i$ are proportional to the $N\times N$ irreducible representations of SU(2). In this sector our model effectively behaves as an N-flation model with $3 N^2$ number of fields and the effective inflaton field has a super-Planckian field value. Furthermore, the fine-tunings associated with unnaturally small couplings in the chaotic type inflationary scenarios are removed. Due to the matrix nature of the inflaton fields there are $3N^2-1$ extra scalar fields in the dynamics. These have the observational effects such as production of iso-curvature perturbations on cosmic microwave background. Moreover, the existence of these extra scalars provides us with a natural preheating mechanism and exit from inflation. As the effective inflaton field can traverse super-Planckian distances in the field space, the model is capable of producing a considerable amount of gravity waves that can be probed by future CMB polarization experiments such as PLANCK, QUIET and CMBPOL.Comment: minor changes, the counting of the alpha and beta modes are corrected, references adde

Null Brane Intersections

We study pairs of planar D-branes intersecting on null hypersurfaces, and other related configurations. These are supersymmetric and have finite energy density. They provide open-string analogues of the parabolic orbifold and null-fluxbrane backgrounds for closed superstrings. We derive the spectrum of open strings, showing in particular that if the D-branes are shifted in a spectator dimension so that they do not intersect, the open strings joining them have no asymptotic states. As a result, a single non-BPS excitation can in this case catalyze a condensation of massless modes, changing significantly the underlying supersymmetric vacuum state. We argue that a similar phenomenon can modify the null cosmological singularity of the time-dependent orbifolds. This is a stringy mechanism, distinct from black-hole formation and other strong gravitational instabilities, and one that should dominate at weak string coupling. A by-product of our analysis is a new understanding of the appearance of 1/4 BPS threshold bound states, at special points in the moduli space of toroidally-compactified type-II string theory.Comment: Tex file, uses harvmac, 24 pages with 5 figures. Corrected typos and added references. Final version to appear in JHE

On the effective action of confining strings

We study the low-energy effective action on confining strings (in the fundamental representation) in SU(N) gauge theories in D space-time dimensions. We write this action in terms of the physical transverse fluctuations of the string. We show that for any D, the four-derivative terms in the effective action must exactly match the ones in the Nambu-Goto action, generalizing a result of Luscher and Weisz for D=3. We then analyze the six-derivative terms, and we show that some of these terms are constrained. For D=3 this uniquely determines the effective action for closed strings to this order, while for D>3 one term is not uniquely determined by our considerations. This implies that for D=3 the energy levels of a closed string of length L agree with the Nambu-Goto result at least up to order 1/L^5. For any D we find that the partition function of a long string on a torus is unaffected by the free coefficient, so it is always equal to the Nambu-Goto partition function up to six-derivative order. For a closed string of length L, this means that for D>3 its energy can, in principle, deviate from the Nambu-Goto result at order 1/L^5, but such deviations must always cancel in the computation of the partition function. Next, we compute the effective action up to six-derivative order for the special case of confining strings in weakly-curved holographic backgrounds, at one-loop order (leading order in the curvature). Our computation is general, and applies in particular to backgrounds like the Witten background, the Maldacena-Nunez background, and the Klebanov-Strassler background. We show that this effective action obeys all of the constraints we derive, and in fact it precisely agrees with the Nambu-Goto action (the single allowed deviation does not appear).Comment: 71 pages, 7 figures. v2: added reference, minor corrections. v3: removed one term from the effective action since it is trivial. The conclusions on the corrections to energy levels are unchanged, but the claim that the holographic computation shows a deviation from Nambu-Goto was modified. v4: added reference