Supersymmetric GUT with stabilized moduli

Nuclear Physics B, 2005

We show that type I string theory compactified in four dimensions in the presence of constant internal magnetic fields possesses N = 1 supersymmetric vacua, in which all Kähler class and complex structure closed string moduli are fixed. Furthermore, their values can be made arbitrarily large by a suitable tuning of the quantized magnetic fluxes. We present an explicit example for the toroidal compactification on T 6 and discuss Calabi-Yau generalizations. This mechanism can be complementary to other stabilization methods using closed string fluxes but has the advantage of having an exact string description and thus a validity away from the low-energy supergravity approximation. Moreover, it can be easily implemented in constructions of string models based on intersecting D-branes. * On leave of absence from CPHT, Ecole Polytechnique, UMR du CNRS 7644.

Nuclear Physics B, 2008

Closed string moduli stabilization has been intensively studied during the last years for its implication towards a comprehensive understanding of the superstring vacua [1] and [2], as well as due to its significance in deriving definite low energy predictions for particle models derived ...

We construct six stack D6-brane vacua (non-supersymmetric) that have at low energy exactly the standard model (with right handed neutrinos). The construction is based on D6-branes intersecting at angles in D = 4 type toroidal orientifolds of type-I strings. Three U(1)'s become massive through their couplings to RR fields and from the three surviving massless U(1)'s at low energies, one is the standard model hypercharge generator. The two extra massless U(1)'s get broken, as suggested recently (hep-th/0205147), by requiring some intersections to respect N = 1 supersymmetry thus supporting the appearance of massless charged singlets. Proton and lepton number are gauged symmetries and their anomalies are cancelled through a generalized Green-Schwarz mechanism that gives masses to the corresponding gauge bosons through couplings to RR fields. Thus proton is stable and neutrinos are of Dirac type with small masses as a result of a PQ like-symmetry. The models predict the existence of only two supersymmetric particles, superpartners of ν R 's.

We show that previous proposals to accommodate the MSSM with string theory N=0 non-supersymmetric compactifications coming from intersecting D6-branes may be made fully consistent with the cancellation of RR tadpoles. In this respect we present the first examples of non-supersymmetric string Pati-Salam model vacua with starting observable gauge group SU (4) c × SU (2) L × SU (2) R (SU(2) from Sp(2)'s) that accommodate the spectrum of the 3 generation MSSM with a gauged baryon number with all extra exotics (either chiral or non-chiral) becoming massive and all MSSM Yukawas realized. These constructions include models with sin 2 (θ W) = 3/8 (SU(5) type) and can have 1, 2 or 4 pairs of higgsinos depending on the # of tilted tori. We work within four dimensional compactifications of IIA theory on toroidal orientifolds without (and with) fluxes. The MSSM spectrum (together with right handed neutrinos) is realized in the intersections of the visible sector that may contain D6-branes whose intersections share the same N=1 supersymmetry. The N=1 supersymmetry of the visible sector is broken by an extra supersymmetry messenger breaking sector that preserves a different N ′ =1 susy, exhibiting the first examples of stringy gauge mediated models. Due to the high scale of the models, these models are also the first realistic examples of carriers of stringy split supersymmetry exhibiting universal slepton/squark masses, massive string scale gauginos, unification of SU(3), SU(2) gauge couplings at 2.04 × 10 16 GeV, a stable proton and the appearance of a landscape split SM with chiral fermions and only Higgsinos below the scale of susy breaking; the LSP neutralino candidate could also be only Higgsino or Higgsino-Wino mixture. We also add RR, NS and metric fluxes as every intersecting D-brane model without fluxes can be accommodated in the presence of fluxes. The addition of metric fluxes in the toroidal lattice also stabilizes the expected real parts of all in AdS closed string moduli (modulo D-term effects), leaving unfixed only the imaginary parts of Kähler moduli.

2015

String theory is one of the most active branches of theoretical physics and constitutes the most promising candidate for a consistent fundamental theory describing our Universe. Its structure provides a uni ed description of all known particles and forces of Nature, including gravity, in a single quantum mechanical framework. Its low-energy limit, determined by compacti cations of extra dimensions on Calabi-Yau orientifolds, yields an e ective theory which represents the key tool in order to make contact with experiments and observable physics. This theory is Supergravity, with the natural presence of a moduli hidden sector, which consists in a collection of gravitationally coupled scalar elds inherited from KaluzaKlein dimensional reduction. In order to avoid non-observed long range fth-forces mediated by massless moduli, these elds have to develop a large mass via the process of moduli stabilisation. The stabilisation of the moduli provides also a dynamical supersymmetry-breaking ...

Physical Review D, 2005

We construct the first D 4 Minkowski string theory vacua of flux compactification which are (i) chiral, (ii) free of NSNS and RR tadpoles, and (iii) N 1 or N 0 supersymmetric. In the latter case SUSY is softly broken by the fluxes, with soft terms being generated in the gauge and chiral sectors of the theory. In addition, the low energy spectrum of the theory is MSSM-like with three generations of chiral matter, the dilaton/complex structure moduli are stabilized and the supergravity background involves a warped metric.

Journal of High Energy Physics, 2007

Anomalous U(1)'s are ubiquitous in 4D chiral string models. Their presence crucially affects the process of moduli stabilisation and cannot be neglected in realistic set-ups. Their net effect in the 4D effective action is to induce a matter field dependence in the non-perturbative superpotential and a Fayet-Iliopoulos D-term. We study flux compactifications of IIB string theory in the presence of magnetised D7 branes. These give rise to anomalous U(1)'s that modify the standard moduli stabilisation procedure. We consider simple orientifold models to determine the matter field spectrum and the form of the effective field theory. We apply our results to one-modulus KKLT and multi-moduli large volume scenarios, in particular to the Calabi-Yau IP 4 [1,1,1,6,9] . After stabilising the matter fields, the effective action for the Kähler moduli can acquire an extra positive term that can be used for de Sitter lifting with non-vanishing F-and D-terms. This provides an explicit realization of the D-term lifting proposal of [1].

We discuss the construction of four dimensional non-supersymmetric models obtained from configurations of D6-branes intersecting at angles. We present the first examples of string GUT models which break exactly to the Standard Model (SM) at low energy. Even though the models are non supersymmetric (SUSY), the demand that some open string sectors preserve N=1 SUSY creates gauge singlet scalars that break the extra anomaly free U(1)'s generically present in the models, predicting s˜νs˜ν R 's and necessarily creating Majorana mass terms for right handed neutrinos.

2002

We discuss the construction of four dimensional non-supersymmetric models obtained from configurations of D6-branes intersecting at angles. We present the first examples of string GUT models which break exactly to the Standard Model (SM) at low energy. Even though the models are non supersymmetric (SUSY), the demand that some open string sectors preserve N=1 SUSY creates gauge singlet scalars that break the extra anomaly free U(1)’s generically present in the models, predicting sν̃R’s and necessarily creating Majorana mass terms for right handed neutrinos. [email protected] 6: Supersymmetry and Superstrings 1417

Physical Review D, 2003

We present new classes of supersymmetric Standard-like models from type IIA T 6 /(Z 2 × Z 2 ) orientifold with intersecting D6-branes. D6-branes can wrap general supersymmetric three-cycles of T 6 = T 2 × T 2 × T 2 , and any T 2 is allowed to be tilted. The models still suffer from additional exotics, however we obtained solutions with fewer Higgs doublets, as well as models with all three families of left-handed quarks and leptons arising from the same intersecting sector, and examples of a genuine left-right symmetric model with three copies of left-handed and right-handed families of quarks and leptons. * On Sabbatic Leave from the University of Pennsylvania † Exchange Scholar from the University of Pennsylvania