One-loop adjoint masses for non-supersymmetric intersecting branes (original) (raw)
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One-loop adjoint masses for branes at non-supersymmetric angles
This proceeding is based on arXiv:1105.0591 [hep-th] where we consider breaking of supersymmetry in intersecting D-brane configurations by slight deviation of the angles from their supersymmetric values. We compute the masses generated by radiative corrections for the adjoint scalars on the brane world-volumes. In the open string channel, the string two-point function receives contributions only from the infrared limits of N~4 and N~2 supersymmetric configurations, via messengers and their Kaluza-Klein excitations, and leads at leading order to tachyonic directions.
Radiative Symmetry Breaking on D-branes at Non-supersymmetric Singularities
2006
The possibility of radiative gauge symmetry breaking on D3-branes at non-supersymmetric orbifold singularities is examined. As an example, a simple model of D3-branes at non-supersymmetric C^3/Z_6 singularity with some D7-branes for the cancellations of R-R tadpoles in twisted sectors is analyzed in detail. We find that there are no tachyon modes in twisted sectors, and NS-NS tadpoles in twisted sectors are canceled out, though uncanceled tadpoles and tachyon modes exist in untwisted sectors. This means that this singularity background is a stable solution of string theory at tree level, though some specific compactification of six-dimensional space should be considered for a consistent untwisted sector. On D3-brane three massless "Higgs doublet fields" and three family "up-type quarks" are realized at tree level. Other fermion fields, "down-type quarks" and "leptons", can be realized as massless modes of the open strings stretching between D3...
We show how to construct chiral tachyon-free perturbative orientifold models, where supersymmetry is broken at the string scale on a collection of branes while, to lowest order, the bulk and the other branes are supersymmetric. In higher orders, supersymmetry breaking is mediated to the remaining sectors, but is suppressed by the size of the transverse space or by the distance from the brane where supersymmetry breaking primarily occurred. This setting is of interest for orbifold models with discrete torsion, and is of direct relevance for low-scale string models. It can guarantee the stability of the gauge hierarchy against gravitational radiative corrections, allowing an almost exact supergravity a millimeter away from a non-supersymmetric world.
One-loop masses of open-string scalar fields in string theory
Journal of High Energy Physics, 2008
In phenomenological models with D-branes, there are in general open-string massless scalar fields, in addition to closed-string massless moduli fields corresponding to the compactification. It is interesting to focus on the fate of such scalar fields in models with broken supersymmetry, because no symmetry forbids their masses. The one-loop effect may give non-zero masses to them, and in some cases mass squared may become negative, which means the radiative gauge symmetry breaking. In this article we investigate and propose a simple method for calculating the one-loop corrections using the boundary state formalism. There are two categories of massless open-string scalar fields. One consists the gauge potential fields corresponding to compactified directions, which can be understood as scalar fields in uncompactified space-time (related with Wilson line degrees of freedom). The other consists "gauge potential fields" corresponding to transverse directions of D-brane, which emerge as scalar fields in D-brane world-volume (related with brane moduli fields). The D-brane boundary states with constant backgrounds of these scalar fields are constructed, and one-loop scalar masses are calculated in the closed string picture. Explicit calculations are given in the following four concrete models: one D25-brane with a circle compactification in bosonic string theory, one D9-brane with a circle compactification in superstring theory, D3-branes at a supersymmetric C 3 /Z 3 orbifold singularity, and a model of brane supersymmetry breaking with D3-branes and anti-D7-branes at a supersymmetric C 3 /Z 3 orbifold singularity. We show that the sign of the mass squared has a strong correlation with the sign of the related open-string one-loop vacuum amplitude.
Radiative symmetry breaking in brane models
Nuclear Physics B, 2000
We propose a way to generate the electroweak symmetry breaking radiatively in nonsupersymmetric type I models with string scale in the TeV region. By identifying the Higgs field with a tree-level massless open string state, we find that a negative squared mass term can be generated at one loop. It is finite, computable and typically a loop factor smaller than the string scale, that acts as an ultraviolet cutoff in the effective field theory. When the Higgs open string has both ends confined on our world brane, its mass is predicted to be around 120 GeV, i.e. that of the lightest Higgs in the minimal supersymmetric model for large tan β and m A . Moreover, the string scale turns out to be one to two orders of magnitude higher than the weak scale. We also discuss possible effects of higher order string threshold corrections that might increase the string scale and the Higgs mass.
LHC phenomenology and cosmology of string-inspired intersecting D-brane models
Physical Review D, 2012
1 It appears likewise from experimental evidence of neutrino flavor oscillations by the mixing of different mass eigenstates that the SM has to be extended . The amplitudes of lowest massive Regge excitations that include 2 → 2 scattering processes involving 4 2 extra U(1) gauge symmetries beyond hypercharge have (in general) triangle anomalies, but are cancelled by the Green-Schwarz mechanism . In addition there can be also massive U(1) gauge bosons, which are associated to 4D non-anomalous Abelian gauge symmetries, but however originate from anomalous U(1)'s in six dimensions. In both cases, these U(1) gauge bosons get Stückelberg masses. Since in these D-brane models M s is assumed to be O(TeV), the presence of these generic U(1)'s may be amenable to experimental tests at the LHC .
The field theory of non-supersymmetric brane configurations
Nuclear Physics B, 1998
We identify the 4D field theories living on the world volume of D4 branes in nonsupersymmetric type IIA string theory constructions. They are softly broken N=2 SQCD with the breakings introduced through vevs of the auxilliary fields in the spurion coupling field. Exact solutions of these theories for perturbing soft breakings exist in the literature. We calculate the ratios of string tensions in softly broken N=2 SU(N) gauge theory testing the recently proposed M-theory prediction. The semi-classical result of M-theory is renormalized in the non-supersymmetric models.
Soft branes in supersymmetry-breaking backgrounds
Journal of High Energy Physics, 2012
We revisit the analysis of effective field theories resulting from non-supersymmetric perturbations to supersymmetric flux compactifications of the type-IIB superstring with an eye towards those resulting from the backreaction of a small number of D3-branes. Independently of the background, we show that the low-energy Lagrangian describing the fluctuations of a stack of probe D3-branes exhibits soft supersymmetry breaking, despite perturbations to marginal operators that were not fully considered in some previous treatments. We take this as an indication that the breaking of supersymmetry by D3-branes or other sources may be spontaneous rather than explicit. In support of this, we consider the action of an D3-brane probing an otherwise supersymmetric configuration and identify a candidate for the corresponding goldstino. Contents 1 Introduction 1 2 Non-supersymmetric perturbations to GKP compactifications 4 3 Effective action for D3s 8 3.1 Bosonic action 8 3.2 Fermionic action 13 3.2.1 Abelian case 13 3.2.2 Non-Abelian case 19 4 The soft Lagrangian 21 5 An anti-brane goldstino 27 6 Discussion and concluding remarks 30 A Conventions 33
Spontaneous Gauge Symmetry Breaking in a Non-Supersymmetric D-brane Model
We investigate a D-brane system in which spontaneous gauge symmetry breaking occurs. The system consists of four D3-branes and three anti-D7-branes at C^3/Z_3 singularity. The singularity is blown up by vacuum expectation values of the states of twisted closed string, whose effects appear as Fayet-Iliopoulos terms in low-energy effective field theory. We derive an effective potential for scalar fields in four-dimensional effective field theory using the technique of superstring world-sheet theory. Since there is no supersymmetry in this system, one-loop masses for some scalar fields are considered. We find some stationary and stable vacua in which the original U(2) x U(1)_1 x U(1)_2 x U(3) gauge symmetry is spontaneously broken to U(1) x U(1)' x U(3) gauge symmetry. Both Fayet-Iliopoulos terms and one-loop masses are necessary for the existence of such vacua. We carefully investigate a geometrical aspect of the gauge symmetry breaking. We show that the gauge symmetry breaking is understood as the separation of D3-branes. Some implications to the possibility of low-scale string models are also discussed.
N=1 Locally Supersymmetric Standard Models from Intersecting branes
We construct four dimensional intersecting D6-brane models that have locally the spectrum of the N=1 Supersymmetric Standard Model. All open visible string sectors share the same N=1 supersymmetry. As expected in these supersymmetric classes of models, where the D6-branes wrap a toroidal orientifold of type IIA, the hierarchy may be stabilized if the string scale is low, e.g. below 30 TeV. We analyze the breaking of supersymmetry in the vicinity of the supersymmetric point by turning on complex structure deformations as Fayet-Iliopoulos terms. Positive masses for all squarks and sleptons, to avoid charge/colour breaking minima, may be reached when also two loop contributions may be included. In the ultimate version of the present models N=1 supersymmetry may be broken by gauge mediation. The constructions with four, five and six stacks of D6-branes at M s are build directly. Next by the use of brane recombination we are able to show that there is a continuous, RR homology flow, between six, five and four stack models. Moreover, we examine the gauge coupling constants of the Standard Model SU(3) C , SU(2) L , U(1) Y at the string scale in the presence of a non-zero antisymmetric NS B-field.