Topological effects on string vacua

We review some topological effects on the construction of string flux-vacua. Specifically we study the effects of brane-flux transitions on the stability of D-branes on a generalized tori compactificaction, the transition that a black hole suffers in a background threaded with fluxes and the connections among some Minkowsky vacua solutions.Comment: Prepared for the XII Workshop on Particles and Fields, Mazatlan, Mexico, 5-13 November 2009; 5 page

Freed-Witten anomaly in general flux compactification

Turning on a NS-NS three-form flux in a compact space drives some D-branes to be either Freed-Witten anomalous or unstable to decay into fluxes by the appearance of instantonic branes. By applying T-duality on a toroidal compactification, the NS-flux is transformed into metric fluxes. We propose a T-dual version of the Atiyah-Hirzebruch Spectral Sequence upon which we describe the Freed-Witten anomaly and the brane-flux transition driven by NS and metric fluxes in a twisted torus. The required conditions to cancel the anomaly and the appearance of new instantonic branes are also described. In addition, we give an example in which all D6-branes wrapping Freed-Witten anomaly-free three-cycles in the twisted torus T^6/Z(2)XZ(2) are nevertheless unstable to be transformed into fluxes. Evenmore we find a topological transformation between RR, NS-NS and metric fluxes driven by a chain of instantonic branes.Comment: v3: Shortened version. Examples added. Main results unchange

log(M_Pl/m_3/2)

Flux compactifications of string theory seem to require the presence of a fine-tuned constant in the superpotential. We discuss a scheme where this constant is replaced by a dynamical quantity which we argue to be a `continuous Chern--Simons term'. In such a scheme, the gaugino condensate generates the hierarchically small scale of supersymmetry breakdown rather than adjusting its size to a constant. A crucial ingredient is the appearance of the hierarchically small quantity exp(-) which corresponds to the scale of gaugino condensation. Under rather general circumstances, this leads to a scenario of moduli stabilization, which is endowed with a hierarchy between the mass of the lightest modulus, the gravitino mass and the scale of the soft terms, m_modulus ~ m_3/2 ~ ^2 m_soft. The `little hierarchy' is given by the logarithm of the ratio of the Planck scale and the gravitino mass, ~ log(M_Pl/m_3/2) ~ 4pi^2. This exhibits a new mediation scheme of supersymmetry breakdown, called mirage mediation. We highlight the special properties of the scheme, and their consequences for phenomenology and cosmology.Comment: Based on talks given at PLANCK05, Trieste, Italy and PASCOS05, Gyeongju, Kore

Effects of brane-flux transition on black holes in string theory

Oscar Loaiza-Brito, Kin-ya Oda. Effects of brane-flux transition on black holes in string theory. https://arxiv.org/abs/hep-th/0703033.This is a pre-print of an article published in Journal of High Energy Physics. The final authenticated version is available online at: https://doi.org/10.1088/1126-6708/2007/08/002

Some remarks on the dS conjecture, fluxes and K-theory in IIB toroidal compactifications

In this note we present a description on the implications on the refined dS Swampland conjecture by considering non-BPS states in type IIB toroidal compactifications . We concentrate on a model T-dual to type I theory for which the total K-theory charge of the non-BPS states vanishes on the six-dimensional torus modded out by an orientifold three-plane. Particularly we consider the presence of non-BPS five branes wrapping internal two-cycles. We comment on the instability of this state by the presence of tachyon modes and the apparent violation of the refined dS conjecture at the minimum of the tachyon potential. The conjecture seems to be valid once we take into account that discrete K-theory charge vanishes. We also describe some issues related to the presence of NS-NS fluxes required to stabilize some moduli since they trigger the appearance of Freed-Witten anomalies. Cancellation of these anomalies implies a topological transformation between non-BPS states and fluxes with the same discrete K-theory charge. After the transition we observe that the dS vacuum constructed from the presence of non-BPS states is also unstable.Comment: 9 pages, no figures. (v2) Typos correcte