We present a detailed study of the finite-temperature behaviour of the LARGE Volume type IIB flux compactifications. We show that certain moduli can thermalise at high temperatures. Despite that, their contribution to the finite-temperature effective potential is always negligible and the latter has a runaway behaviour. We compute the maximal temperature T max , above which the internal space decompactifies, as well as the temperature T * , that is reached after the decay of the heaviest moduli. The natural constraint T * < T max implies a lower bound on the allowed values of the internal volume V. We find that this restriction rules out a significant range of values corresponding to smaller volumes of the order V ∼ 10 4 l 6 s , which lead to standard GUT theories. Instead, the bound favours values of the order V ∼ 10 15 l 6 s , which lead to TeV scale SUSY desirable for solving the hierarchy problem. Moreover, our result favours low-energy inflationary scenarios with density perturbations generated by a field, which is not the inflaton. In such a scenario, one could achieve both inflation and TeV-scale SUSY, although gravity waves would not be observable. Finally, we pose a two-fold challenge for the solution of the cosmological moduli problem. First, we show that the heavy moduli decay before they can begin to dominate the energy density of the Universe. Hence they are not able to dilute any unwanted relics. And second, we argue that, in order to obtain thermal inflation in the closed string moduli sector, one needs to go beyond the present EFT description.
We study whether finite temperature corrections decompactify the internal space in KKLT compactifications with an uplifting sector given by a system that exhibits metastable dynamical supersymmetry breaking. More precisely, we calculate the one-loop temperature corrections to the effective potential of the volume modulus in the KKLT model coupled to the quantum corrected O'Raifeartaigh model. We prove that for the original KKLT model, namely with one exponent in the non-perturbative superpotential, the finite temperature potential is runaway when at zero temperature there is a dS minimum.On the other hand, for a non-perturbative superpotential of the race-track type with two exponents, we demonstrate that the temperature-dependent part of the effective potential can have local minima at finite field vevs. However, rather unexpectedly, it turns out that these minima do not affect the structure of the full effective potential and so the volume modulus is stabilized at the local minimum of the zero temperature potential for the whole range of validity of the supergravity approximation.in which the only consequence of the presence of nonvanishing fluxes is the appearance of a warp factor (see [6] for a comprehensive review on flux compactifications). This makes the type IIB set-up much more tractable.Naturally then, the KKLT proposal [4] for dS vacua in type IIB with stabilized moduli attracted a lot of attention. 1 Unfortunately, the need to add by hand anti-D3 branes in order to lift the original AdS vacuum to dS makes it problematic to describe this setup in supergravity. An improvement that does not require anti-D3 branes was proposed in [9]. There, the uplifting is achieved by having nonzero D-terms from world-volume fluxes on D7 branes that wrap a three-cycle in the CY 3-fold. However, because of the relationship between D-and F-terms in supergravity, this scenario turned out to be difficult to realize [10]; although, see [11] for some recent progress. The above difficulties can be circumvented by coupling the KKLT sector to an ISS sector or, more generally, to a field theory sector that exhibits dynamical supersymmetry breaking to a metastable state (for brevity, MDSB) [12]; see also [13]. 2 In this way, one has a natural uplifting that is also completely under control in the effective 4d N = 1 supergravity description. 3In fact, one can capture the essential features of F-term uplifting due to MDSB in the KKLT set-up by taking the uplifting sector to be the O'Raifeartaigh model. The reason is that many theories with dynamical supersymmetry breaking can be approximated near the origin of field space by this model [17]. 4 The O'Raifeartaigh-uplifted KKLT, termed O'KKLT, model was first proposed and studied in [19]. It was pointed out there that the original KKLT proposal, i.e. with one exponent in the superpotential, leads to tension between low scale supersymmetry breaking and the standard high scale cosmological inflation. This undesirable situation can be resolved by considering a racetrack-type superpotenti...
We investigate the dynamics of a pair of coincident D5 branes in the background of k NS5 branes. It has been proposed by Kutasov that the system with a single probing D-brane moving radially in this background is dual to the tachyonic DBI action for a non-BPS Dp brane. We extend this proposal to the non-abelian case and find that the duality still holds provided one promotes the radial direction to a matrix valued field associated with a non-abelian geometric tachyon and a particular parametrization for the transverse scalar fields is chosen. The equations of motion of a pair of coincident D5 branes moving in the NS5 background are determined. Analytic and numerical solutions for the pair are found in certain simplified cases in which the U (2) symmetry is broken to U (1) × U (1) corresponding to a small transverse separation of the pair. For certain range of parameters these solutions describe periodic motion of the centre of mass of the pair 'bouncing off' a finite sized throat whose minimum size is limited by the D5 branes separation.
Starting from the action of two coincident non-BPS D9-branes, we investigate kink configurations of the U(2) matrix tachyon field. We consider both Str and T r prescriptions for the trace over gauge indices of the non-BPS action. Nonabelian tachyon condensation in the theory with T r prescription, and the resulting fluctuations about the kink profile, are shown to give rise to a theory of two coincident BPS D8-branes. This is a natural non-abelian generalization of Sen's mechanism of tachyon condensation on a single non-BPS Dp-brane yielding a single BPS brane of codimesion one. By contrast, starting with the Str gauge trace prescription of the coincident non-BPS D9-brane action, such a generalization of Sen's mechanism appears problematic.
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