827 research outputs found

### New Attractors and Area Codes

In this note we give multiple examples of the recently proposed New
Attractors describing supersymmetric flux vacua and non-supersymmetric extremal
black holes in IIB string theory. Examples of non-supersymmetric extremal black
hole attractors arise on a hypersurface in $WP^{4}_{1,1,1,1,2}$. For flux vacua
on the orientifold of the same hypersurface existence of multiple basins of
attraction is established. It is explained that certain fluxes may give rise to
multiple supersymmetric flux vacua in a finite region on moduli space, say at
the Landau-Ginzburg point and close to conifold point. This suggests the
existence of multiple basins for flux vacua and domain walls in the landscape
for a fixed flux and at interior points in moduli space.Comment: 16 pages, harvmac. v2: acknowledgement update

### Bounds on Scalar Masses in Theories of Moduli Stabilization

In recent years it has been realised that pre-BBN decays of moduli can be a
significant source of dark matter production, giving a `non-thermal WIMP
miracle' and substantially reduced fine-tuning in cosmological axion physics.
We study moduli masses and sharpen the claim that moduli dominated the pre-BBN
Universe. We conjecture that in any string theory with stabilized moduli there
will be at least one modulus field whose mass is of order (or less than) the
gravitino mass. Cosmology then generically requires the gravitino mass not be
less than about 30 TeV and the cosmological history of the Universe is
non-thermal prior to BBN. Stable LSP's produced in these decays can account for
the observed dark matter if they are `wino-like.' We briefly consider
implications for the LHC, rare decays, and dark matter direct detection and
point out that these results could prove challenging for models attempting to
realize gauge mediation in string theory.Comment: 7 pages. v3: published versio

### From Defects to Boundaries

In this paper we describe how relativistic field theories containing defects
are equivalent to a class of boundary field theories. As a consequence
previously derived results for boundaries can be directly applied to defects,
these results include reduction formulas, the Coleman-Thun mechanism and
Cutcosky rules. For integrable theories the defect crossing unitarity equation
can be derived and defect operator found. For a generic purely transmitting
impurity we use the boundary bootstrap method to obtain solutions of the defect
Yang-Baxter equation. The groundstate energy on the strip with defects is also
calculated.Comment: 14 pages, 10 figures. V2 Removed comparison to RT algebras and added
paragraph on the usefulness of transmitting defects in the study of boundary
systems. References added. V3 Extended to include application to defect TB

### A Closer Look at Two $AdS_4$ Branes in an $AdS_5$ Bulk

We investigate a scenario with two $AdS_4$ branes in an $AdS_5$ bulk. In this
scenario there are two gravitons and we investigate the role played by each of
them for different positions of the second brane. We show that both gravitons
play a significant role only when the turn-around point in the warp factor is
approximately equidistant from both branes. We find that the ultralight mode
becomes heavy as the second brane approaches the turn-around point, and the
physics begins to resemble that of the RS model. Thus we demonstrate the
crucial role played by the turn-around in the warp factor in enabling the
presence of both gravitons.Comment: 21 pages, late

### Nonsupersymmetric brane vacua in stabilized compactifications

We derive the equations for the nonsupersymmetric vacua of D3-branes in the
presence of nonperturbative moduli stabilization in type IIB flux
compactifications, and solve and analyze them in the case of two particular
7-brane embeddings at the bottom of the warped deformed conifold. In the limit
of large volume and long throat, we obtain vacua by imposing a constraint on
the 7-brane embedding. These vacua fill out continuous spaces of higher
dimension than the corresponding supersymmetric vacua, and have negative
effective cosmological constant. Perturbative stability of these vacua is
possible but not generic. Finally, we argue that anti-D3-branes at the tip of
the conifold share the same vacua as D3-branes.Comment: 17 pages, 1 figure, LaTeX. v2: references added, typo fixed. v3:
version appearing in JHE

### Q-instantons

We construct the half-supersymmetric instanton solutions that are
electric-magnetically dual to the recently discussed half-supersymmetric
Q7-branes. We call these instantons `Q-instantons'. Whereas the D-instanton is
most conveniently described using the RR axion \chi and the dilaton \phi, the
Q-instanton is most conveniently described using a different set of fields
\chi' and T, where \chi' is an axionic scalar. The real part of the Q-instanton
on-shell action is a function of T and the imaginary part is linear in \chi'.
Discrete shifts of the axion \chi' correspond to PSL(2,Z) transformations that
are of finite order. These are e.g. pure S-duality transformations relating
weak and strongly coupled regimes. We argue that near each orbifold point of
the quantum axion-dilaton moduli space PSL(2,Z)\PSL(2,R)/SO(2) the higher order
R^4 terms in the string effective action contain contributions from an infinite
sum of single multiply-charged instantons with the Q-instantons corresponding
to the orbifold points \tau=i,\rho where \tau is the complex axion-dilaton
field.Comment: 29 pages, 1 figur

### Quiver Theories from D6-branes via Mirror Symmetry

We study N=1 four dimensional quiver theories arising on the worldvolume of
D3-branes at del Pezzo singularities of Calabi-Yau threefolds. We argue that
under local mirror symmetry D3-branes become D6-branes wrapped on a three torus
in the mirror manifold. The type IIB (p,q) 5-brane web description of the local
del Pezzo, being closely related to the geometry of its mirror manifold,
encodes the geometry of 3-cycles and is used to obtain gauge groups, quiver
diagrams and the charges of the fractional branes.Comment: 30 pages, citations adde

### Non-simply-laced Lie algebras via F theory strings

In order to describe the appearance in F theory of the non--simply--laced Lie
algebras, we use the representation of symmetry enhancements by means of string
junctions. After an introduction to the techniques used to describe symmetry
enhancement, that is algebraic geometry, BPS states analysis and string
junctions, we concentrate on the latter. We give an explicit description of the
folding of D_{2n} to B_n of the folding of E_6 to F_4 and that of D_4 to G_2 in
terms of junctions and Jordan strings. We also discuss the case of C_n, but we
are unable in this case to provide a string interpretation.Comment: 24 pages, 3 figure

### Bloch Brane

We investigate a system described by two real scalar fields coupled with
gravity in (4, 1) dimensions in warped spacetime involving one extra dimension.
The results show that the parameter which controls the way the two scalar
fields interact induces the appearence of thick brane which engenders internal
structure, driving the energy density to localize inside the brane in a very
specific way.Comment: 13 pages, 6 figures; some misprints corrected, to appear in JHE

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