| 1. |
- Bena, I., et al.
(författare)
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Antibranes cannot become black
- 2013
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 87:10, s. 104023-
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Tidskriftsartikel (refereegranskat)abstract
- When D-branes are inserted in flux backgrounds of opposite charge, the resulting solution has a certain singularity in the fluxes. Recently it has been argued, using numerical solutions, that for anti-D3 branes in the Klebanov-Strassler background, these singularities cannot be cloaked by a horizon, which strongly suggests they are not physical. In this paper we provide an analytic proof that the singularity of all codimension-three antibrane solutions (such as anti-D6 branes in massive type IIA supergravity or anti-D3 branes smeared on the T-3 of R-3 x T-3 with fluxes) cannot be hidden behind a horizon and that the charge of black branes with smooth event horizons must have the same sign as the charge of the flux background. Our result indicates that infinitesimally blackening the antibranes immediately triggers brane-flux annihilation and strengthens the intuition that antibranes placed in flux with positive charge immediately annihilate against it.
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| 2. |
- Blåbäck, Johan, et al.
(författare)
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A new light on the darkest corner of the landscape
- 2018
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- otivated by the recently proposed bounds on the slow-roll parameters forscalar potentials arising from string/M-theory compactifications, a.k.a. theRefined de Sitter Swampland conjecture, we explore the sharpness of suchconstraints within 4D supergravities coming from compactifications of massivetype IIA string theory onT6/(Z2×Z2). With the aid of a numerical technique,known as differential evolution, we are able to find a de Sitter extremum whichis fully metastable up to one single flat direction. This solution is supported byspacetime filling sources such as O6 planes and KK monopoles. Our exampleviolates the bound imposed by this conjecture
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| 3. |
- Blåbäck, Johan, et al.
(författare)
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Accelerated Universes from type IIA Compactifications
- 2014
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :003
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We study slow-roll accelerating cosmologies arising from geometric compactifications of type IIA string theory on T^6/(Z_2 x Z_2). With the aid of a genetic algorithm, we are able to find quasi-de Sitter backgrounds with both slow-roll parameters of order 0.1
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| 4. |
- Blåbäck, Johan, et al.
(författare)
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(Anti-)brane backreaction beyond perturbation theory
- 2012
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; 2012:2, s. 025-
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Tidskriftsartikel (refereegranskat)abstract
- We improve on the understanding of the backreaction of anti-D6-branes in a flux background that is mutually BPS with D6-branes. This setup is analogous to the study of the backreaction of anti-D3-branes inserted in the KS throat, but does not require us to smear the anti-branes or do a perturbative analysis around the BPS background. We solve the full equations of motion near the anti-D6-branes and show that only two boundary conditions are consistent with the equations of motion. Upon invoking a topological argument we eliminate the boundary condition with regular H flux since it cannot lead to a solution that approaches the right kind of flux away from the anti-D6-branes. This leaves us with a boundary condition which has singular, but integrable, H flux energy density.
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| 5. |
- Blåbäck, Johan, et al.
(författare)
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BPS domain walls from backreacted orientifolds
- 2014
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :5, s. 040-
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Tidskriftsartikel (refereegranskat)abstract
- Compactifications with D-brane and orientifold sources lead to standard gauged supergravity theories if the sources are smeared over the internal directions. It is therefore of interest to find how the solutions described by the gauged supergravity are altered by properly localising the sources. In this paper we analyse this for BPS domain wall solutions in the seven-dimensional gauged supergravity obtained from an O6 toroidal orientifold in massive IIA supergravity. This is one of the simplest no-scale supergravities that can be constructed and analysed in full detail. We find the BPS domain walls when the O6 planes are smeared. When the O6 planes are localised the domain wall solutions live in a warped compactification and we present the first-order equations these domain walls obey in 10 dimensions. In order to get explicit expressions we also consider the non-compact versions of the solutions for which the O6 planes have been traded for D6 branes and we recover the gauged supergravity expressions for the domain walls in the leading terms of the warp factor. Through T-duality we obtain partially localised solutions for compactifications to four dimensions using O3 planes with 3-form fluxes.
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| 6. |
- Blåbäck, Johan, et al.
(författare)
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de Sitter vacua from nonperturbative flux compactifications
- 2014
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 90:2, s. 024065-
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present stable de Sitter solutions of =1 supergravity in a geometric type IIB duality frame with the addition of non-perturbative contributions. Contrary to the standard approach we retain the moduli dependence of both the tree level superpotential and its non-perturbative contribution. This provides the possibility for a single-step approach that stabilises all moduli simultaneously in a de Sitter vacuum. By means of a genetic algorithm we find explicit solutions where different scales are separated and hierarchies are investigated.
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| 7. |
- Blåbäck, Johan, et al.
(författare)
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Fractional branes, warped compactifications and backreacted orientifold planes
- 2012
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; 2012:10
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Tidskriftsartikel (refereegranskat)abstract
- The standard extremal p-brane solutions in supergravity are known to allow for a generalisation which consists of adding a linear dependence on the worldvolume coordinates to the usual harmonic function. In this note we demonstrate that remarkably this generalisation goes through in exactly the same way for p-branes with fluxes added to it that correspond to fractional p-branes. We relate this to warped orientifold compactifications by trading the Dp-branes for Op-planes that solve the RR tadpole condition. This allows us to interpret the worldvolume dependence as due to lower-dimensional scalars that flow along the massless directions in the no-scale potential. Depending on the details of the fluxes these flows can be supersymmetric domain wall flows. Our solutions provide explicit examples of backreacted orientifold planes in compactifications with non-constant moduli.
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| 8. |
- Blåbäck, Johan, et al.
(författare)
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Fully stable dS vacua from generalised fluxes
- 2013
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; 8, s. 054-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the possible existence of (meta-)stable de Sitter vacua within \cN=1 compactifications with generalised fluxes. With the aid of an algorithm inspired by the method of differential evolution, we were able to find three novel examples of completely tachyon-free de Sitter extrema in a non-isotropic type IIB model with non-geometric fluxes. We also analyse the surroundings of the aforementioned points in parameter space and chart the corresponding stability regions. These happen to occur at small values of the cosmological constant compared to the AdS scale.
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| 9. |
- Blåbäck, Johan, et al.
(författare)
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Localised anti-branes in non-compact throats at zero and finite T
- 2015
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :2
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the 3-form singularities that are typical to anti-brane solutions in supergravity and check whether they can be cloaked by a finite temperature horizon. For anti-D3-branes in the Klebanov-Strassler background, this was already shown numerically to be impossible when the branes are partially smeared. In this paper, we present analytic arguments that also localised branes remain with singular 3-form fluxes at both zero and finite temperature. These results may have important, possibly fatal, consequences for constructions of meta-stable de Sitter vacua through uplifting.
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| 10. |
- Blåbäck, Johan
(författare)
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Note on M2-branes in opposite charge
- 2014
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 89:6, s. 065004-
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Tidskriftsartikel (refereegranskat)abstract
- The flux singularity that arises for branes in oppositely charged fluxes is a widely discussed issue and in this paper the problem is investigated further. New AdS world volume (anti-)M2-brane solutions are constructed using space-filling branes placed in fluxes of opposite dissolved charge that is opposite to that of the brane. A topological obstruction is derived to show how the singularity develops during localization of this solution and any similarly constructed solution. Furthermore it is shown that it is not possible to hide the singularity behind a horizon, which would have given credence to an M theory resolution.
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