1,721,003 research outputs found
Type IIB flux vacua from M-theory via F-theory
No full textWe study in detail some aspects of duality between type IIB and M-theory. We focus on the duality between type IIB string theory on K3 x T-2/Z(2) orientifold and M-theory on K3 x K3, in the F-theory limit. We give the explicit map between the fields and in particular between the moduli of compactification, studying their behavior under the F-theory limit. Turning on fluxes generates a potential for the moduli both in type IIB and in M-theory. We verify that the type IIB analysis gives the same results of the F-theory analysis. In particular we check that the two potentials match
Phenomenology from the Landscape of String Vacua
Full text linkThis article is the author's PhD thesis. After a review of string vacua obtained through compactification (with and wothout fluxes), it presents and describes various aspects of the Landscape of string vacua. At first it gives an introduction and an overview of the statistical study of the set of four dimensional string vacua, giving the detailed study of one corner of this set (G2-holonomy compactifications of M-theory). Then it presents the ten dimensional approach to string vacua, concentrating on the ten dimensional description of the Type IIA flux vacua. Finally it gives two examples of models having some interesting and characteristic phenomenological features, and that belong to two different corners of the Landscape: warped compactifications of Type IIB String Theory and M-theory compactifications on G2-holonomy manifolds
Type IIA/M-theory moduli fixing in a class of orientifold models
No full textWe present the study of type II A flux vacua and their M-theory duals for compactification on a class of Calabi-Yau orientifolds. The Kähler potential is derived from toroidal compactifications and the superpotential contains a contribution from non-Abelian gauge degrees of freedoms. We obtain complete stabilisation of the moduli. We found one supersymmetric minimum and several non supersymmetric ones. Consistency of the analysis constrains the parameters of the models in a finite region containing a finite, although very large, number of flux vacua. From the M-theory side, we found some differences in the distributions of the physical quantities with respect to the M-theory ensemble studied by Acharya et al [1]. In particular, it is easier to find small supersymmetry breaking scale
Heterotic-type II duality in the hypermultiplet sector
No full textWe revisit the duality between heterotic string theory compactified on K3 x T-2 and type IIA compactified on a Calabi-Yau threefold X in the hypermultiplet sector. We derive an explicit map between the field variables of the respective moduli spaces at the level of the classical effective actions. We determine the parametrization of the K3 moduli space consistent with the Ferrara-Sabharwal form. From the expression of the holomorphic prepotential we are led to conjecture that both X and its mirror must be K3 fibrations in order for the type IIA theory to have an heterotic dual. We then focus on the region of the moduli space where the metric is expressed in terms of a prepotential on both sides of the duality. Applying the duality we derive the heterotic hypermultiplet metric for a gauge bundle which is reduced to 24 point-like instantons. This result is confirmed by using the duality between the heterotic theory on T-3 and M-theory on K3. We finally study the hyper-Kahler metric on the moduli space of an SU(2) bundle on K3
Suppressing proton decay in theories with localised fermions
No full textWe calculate the contribution to the proton decay amplitude from Kaluza-Klein lepto-quarks in theories with extra dimensions, localised fermions and gauge fields which propagate in the bulk. Such models naturally occur within the context of M theory. In SU(5) models we show that carefully including all such modes gives a distinctive pattern of decays through various channels including a strong suppression of decays into neutrinos or right handed positrons. By contrast there is no such suppression for SO(10)
6D effective action of heterotic compactification on K3 with nontrivial gauge bundles
No full textWe compute the six-dimensional effective action of the heterotic string compactified on K3 for the standard embedding and for a class of backgrounds with line bundles and appropriate Yang-Mills fluxes. We compute the couplings of the charged scalars and the bundle moduli as functions of the geometrical K3 moduli from a Kaluza-Klein analysis. We derive the D-term potential and show that in the flux backgrounds U (1) vector multiplets become massive by a Stückelberg mechanism
M-theory geometric engineering for rank-0 3d N=2 theories
No full textM-theory geometric engineering on non-compact Calabi-Yau fourfolds (CY4) produces 3d theories with 4 supercharges. Carefully establishing a dictionary between the geometry of the CY4 and the QFT in the transverse directions remains, to a large extent, an unresolved challenge, complicated by subtleties arising from M5-brane instanton corrections. Such difficulties can be circumvented in the restricted and yet controlled setting offered by CY4 with terminal singularities, as they do not admit crepant resolutions with compact exceptional divisors. After a general review of their properties and partial classifications, we focus on a subclass of terminal CY4 constructed as deformed Du Val singularities, that admit crepant resolutions with at most exceptional 2-cycles. We extract the corresponding 3d N = 2 supersymmetric theory descendant in an unambiguous fashion, as the absence of compact 4-cycles leaves no room for a choice of background G4 flux. These turn out to be theories of chiral multiplets with no gauge group and at most abelian flavor factors: we argue that they serve as the simplest building blocks to substantiate a rigorous CY4/3d QFT geometric engineering mapping
Algebraic description of G-flux in F-theory: new techniques for F-theory phenomenology
No full textWe give a global algebraic description of the four-form flux in F-theory. We present how to compute its D3-tadpole and how to calculate the number of four-dimensional chiral states at the intersection of 7-branes directly in F-theory. We check that, in the weak coupling limit, we obtain the same results as using perturbative type IIB string theory. We develop these techniques in full generality. However, they can be readily applied to concrete models, as we show in an explicit example.We give a global algebraic description of the four-form flux in F-theory. We present how to compute its D3-tadpole and how to calculate the number of four-dimensional chiral states at the intersection of 7-branes directly in F-theory. We check that, in the weak coupling limit, we obtain the same results as using perturbative type IIB string theory. We develop these techniques in full generality. However, they can be readily applied to concrete models, as we show in an explicit example
Weierstrass meets Enriques
No full textWe study in detail the degeneration of K3 to T-4/Z(2). We obtain an explicit embedding of the lattice of collapsed cycles of T-4/Z(2) into the lattice of integral cycles of K3 in two different ways. Our first method exploits the duality to the heterotic string on T-3. This allows us to describe the degeneration in terms of Wilson lines. Our second method is based on the blow-up of T-4/Z(2). From this blow-up, we directly construct the full lattice of integral cycles of K3. Finally, we use our results to describe the action of the Enriques involution on elliptic K3 surfaces, finding that a Weierstrass model description is consistent with the Enriques involution only in the F-theory limit
Fixing D7-brane positions by F-theory fluxes
No full textTo do realistic model building in type IIB supergravity, it is important to understand how to fix D7-brane positions by the choice of fluxes. More generally, F-theory model building requires the understanding of how fluxes determine the singularity structure (and hence gauge group and matter content) of the compactification. We analyse this problem in the simple setting of M-theory on K3 x K3. Given a certain flux which is consistent with the F-theory limit. we can explicitly derive the positions at which D7 branes or Stacks of D7 branes are stabilised. The analysis is based on a parameterization of the moduli space of type IIB string theory on T(2)/Z(2) (including D7-brane positions) in terms of the periods of the periods of integral cycles of M-theory on K3. This allows us. in particular, to select a specific desired gauge group by the choice of flux numbers
- …
