Exceptional Flux Compactifications

We consider type II (non-)geometric flux backgrounds in the absence of brane sources, and construct their explicit embedding into maximal gauged D=4 supergravity. This enables one to investigate the critical points, mass spectra and gauge groups of such backgrounds. We focus on a class of type IIA geometric vacua and find a novel, non-supersymmetric and stable AdS vacuum in maximal supergravity with a non-semisimple gauge group. Our construction relies on a non-trivial mapping between SL(2) x SO(6,6) fluxes, SU(8) mass spectra and gaugings of E7(7) subgroups.Comment: 51 pages, 2 figures and 4 tables. v3: change of SO(6,6) spinorial conventions, published versio

Charting the landscape of N=4 flux compactifications

We analyse the vacuum structure of isotropic Z_2 x Z_2 flux compactifications, allowing for a single set of sources. Combining algebraic geometry with supergravity techniques, we are able to classify all vacua for both type IIA and IIB backgrounds with arbitrary gauge and geometric fluxes. Surprisingly, geometric IIA compactifications lead to a unique theory with four different vacua. In this case we also perform the general analysis allowing for sources compatible with minimal supersymmetry. Moreover, some relevant examples of type IIB non-geometric compactifications are studied. The computation of the full N=4 mass spectrum reveals the presence of a number of non-supersymmetric and nevertheless stable AdS_4 vacua. In addition we find a novel dS_4 solution based on a non-semisimple gauging.Comment: Minor corrections and references added. Version published in JHE

Stability Constraints on Classical de Sitter Vacua

We present further no-go theorems for classical de Sitter vacua in Type II string theory, i.e., de Sitter constructions that do not invoke non-perturbative effects or explicit supersymmetry breaking localized sources. By analyzing the stability of the 4D potential arising from compactification on manfiolds with curvature, fluxes, and orientifold planes, we found that additional ingredients, beyond the minimal ones presented so far, are necessary to avoid the presence of unstable modes. We enumerate the minimal setups for (meta)stable de Sitter vacua to arise in this context.Comment: 18 pages; v2: argument improved, references adde

Classification of non-Riemannian doubled-yet-gauged spacetime

Assuming $\mathbf{O}(D,D)$ covariant fields as the `fundamental' variables, Double Field Theory can accommodate novel geometries where a Riemannian metric cannot be defined, even locally. Here we present a complete classification of such non-Riemannian spacetimes in terms of two non-negative integers, $(n,\bar{n})$, $0\leq n+\bar{n}\leq D$. Upon these backgrounds, strings become chiral and anti-chiral over $n$ and $\bar{n}$ directions respectively, while particles and strings are frozen over the $n+\bar{n}$ directions. In particular, we identify $(0,0)$ as Riemannian manifolds, $(1,0)$ as non-relativistic spacetime, $(1,1)$ as Gomis-Ooguri non-relativistic string, $(D{-1},0)$ as ultra-relativistic Carroll geometry, and $(D,0)$ as Siegel's chiral string. Combined with a covariant Kaluza-Klein ansatz which we further spell, $(0,1)$ leads to Newton-Cartan gravity. Alternative to the conventional string compactifications on small manifolds, non-Riemannian spacetime such as $D=10$, $(3,3)$ may open a new scheme of the dimensional reduction from ten to four.Comment: 1+41 pages; v2) Refs added; v3) Published version; v4) Sign error in (2.51) correcte

Universal de Sitter solutions at tree-level

Type IIA string theory compactified on SU(3)-structure manifolds with orientifolds allows for classical de Sitter solutions in four dimensions. In this paper we investigate these solutions from a ten-dimensional point of view. In particular, we demonstrate that there exists an attractive class of de Sitter solutions, whose geometry, fluxes and source terms can be entirely written in terms of the universal forms that are defined on all SU(3)-structure manifolds. These are the forms J and Omega, defining the SU(3)-structure itself, and the torsion classes. The existence of such universal de Sitter solutions is governed by easy-to-verify conditions on the SU(3)-structure, rendering the problem of finding dS solutions purely geometrical. We point out that the known (unstable) solution coming from the compactification on SU(2)x SU(2) is of this kind.Comment: 20 pages, 3 figures, v2: added reference

Matrix theory origins of non-geometric fluxes

We explore the origins of non-geometric fluxes within the context of M theory described as a matrix model. Building upon compactifications of Matrix theory on non-commutative tori and twisted tori, we formulate the conditions which describe compactifications with non-geometric fluxes. These turn out to be related to certain deformations of tori with non-commutative and non-associative structures on their phase space. Quantization of flux appears as a natural consequence of the framework and leads to the resolution of non-associativity at the level of the unitary operators. The quantum-mechanical nature of the model bestows an important role on the phase space. In particular, the geometric and non-geometric fluxes exchange their properties when going from position space to momentum space thus providing a duality among the two. Moreover, the operations which connect solutions with different fluxes are described and their relation to T-duality is discussed. Finally, we provide some insights on the effective gauge theories obtained from these matrix compactifications.Comment: 1+31 pages, reference list update

Duality Invariant M-theory: Gauged supergravities and Scherk-Schwarz reductions

We consider the reduction of the duality invariant approach to M-theory by a U-duality group valued Scherk-Schwarz twist. The result is to produce potentials for gauged supergravities that are normally associated with non-geometric compactifications. The local symmetry reduces to gauge transformations with the gaugings exactly matching those of the embedding tensor approach to gauged supergravity. Importantly, this approach now includes a nontrivial dependence of the fields on the extra coordinates of the extended space.Comment: 22 pages Latex; v2: typos corrected and references adde

Formation and nucleolytic processing of Cas9-induced DNA breaks in human cells quantified by droplet digital PCR

Cas9 endonuclease from S. pyogenes is widely used to induce controlled double strand breaks (DSB) at desired genomic loci for gene editing. Here, we describe a droplet digital PCR (ddPCR) method to precisely quantify the kinetic of formation and 5\u2032-end nucleolytic processing of Cas9-induced DSB in different human cells lines. Notably, DSB processing is a finely regulated process, which dictates the choice between non-homologous end joining (NHEJ) and homology directed repair (HDR). This step of DSB repair is also a relevant point to be taken into consideration to improve Cas9-mediated technology. Indeed, by this protocol, we show that processing of Cas9-induced DSB is impaired by CTIP or BRCA1 depletion, while it is accelerated after down-regulation of DNAPKcs and 53BP1, two DSB repair key factors. In conclusion, the method we describe here can be used to study DSB repair mechanisms, with direct utility for molecularly optimising the knock-out/in outcomes in genome manipulation

Critical points of maximal D=8 gauged supergravities

We study the general deformations of maximal eight-dimensional supergravity by using the embedding tensor approach. The scalar potential induced by these gaugings is determined. Subsequently, by combining duality covariance arguments and algebraic geometry techniques, we find the complete set of critical points of the scalar potential. Remarkably, up to SO(2) X SO(3) rotations there turns out to be a unique theory admitting extrema. The gauge group of the theory is CSO(2,0,1).Comment: 14 pages. v2: minor changes - published versio

The scaffold protein SLX4/FANCP plays a conserved role in early steps of homologous recombination DNA repair

Both in yeast and mammals, the scaffold protein SLX4/FANCP has been implicated in late steps of homologous recombination DNA repair, delivering the structure specific nucleases MUS81, SLX1 and XPF/RAD1 onto DNA repair intermediates (such as joint molecules and 3\u2019 non homologous DNA flap). Working with the model organism S. cerevisiae, we showed that Slx4 competes with the 53BP1-ortholog Rad9 for DSB end binding, favoring DNA end resection and homologous recombination repair. To investigate a possible conservation of the pathway, we exploited the AsiSI restriction enzyme and Cas9-based systems to study SLX4 role in controlling DSB resection in U2OS human osteosarcoma cells and FANCP patient derived fibroblasts. We also analyzed homologous recombination DNA repair through standard GFP reporter cassette assays and immunofluorescence foci of specific factors. The obtained results indicate that down regulation of SLX4/FANCP limits DSB resection and repair, supporting an important conserved SLX4/FANCP role in early steps of homologous recombination DNA repair, independently of the nucleases MUS81 and XPF