Geometry of orientifold vacua and supersymmetry breaking

Abstract

Starting from a peculiar orientifold projection proposed long ago by Angelantonj and Cardella, we elaborate on a novel perturbative scenario that involves only D-branes, together with the two types of orientifold planes O± and anti-orientifold planes $$ {\overline{\mathrm{O}}}_{\pm } $$ O ¯ ± . We elucidate the microscopic ingredients of such models, connecting them to a novel realization of brane supersymmetry breaking. Depending on the position of the D-branes in the internal space, supersymmetry can be broken at the string scale on branes, or alternatively only at the massive level. The main novelty of this construction is that it features no NS-NS disk tadpoles, while avoiding open-string instabilities. The one-loop potential, which depends on the positions of the D-branes, is minimized for maximally broken, non-linearly realized supersymmetry. The orientifold projection and the effective field theory description reveal a soft breaking of supersymmetry in the closed-string sector. In such models it is possible to decouple the gravitino mass from the value of the scalar potential, while avoiding brane instabilities.

Supersymmetry breaking, brane dynamics and the swampland

“…Recent considerations in the context of the swampland program [10][11][12][13] also support the naturalness of string-scale supersymmetry breaking. In particular, the gravitino mass appears to play an important role, and resonates with the phenomenon of BSB, as discussed in [14].…”

Super No-Scale Models with Pati-Salam Gauge Group

“…In this language T 1 , T 2 , T 3 are associated with orbifold shifts along the three internal 2-tori. The addition of z 1 , z 2 reduces the hidden SO(18) gauge symmetry to U (1) × SO(8) 2 , while α breaks the observable SO (10) group to the Pati-Salam gauge symmetry SO(6) × SO(4) ∼ SU (4) × SU (2) L × SU (2) R and further reduces the hidden gauge group SO(8) 2 →SO(4) 2 × SO(8) ∼ SU (2) 4 × SO (8). Altogether, the models possess…”

“…which appear in the spectrum when P φ z 1 = 1, φ ∈ {η 1,2,3 }, lead to the gauge symmetry enhancement (8) to SO (12) and are present when P φ z 1 = 1, φ ∈ { φ5,...,8 }. Likewise, in z 2 , the states (12).…”

“…If supersymmetry is realized in nature, it must be broken spontaneously and the determination of the precise mechanism as well as the scale of the breaking, within a fully-fledged stringy setup, remain important open problems. Non-supersymmetric string constructions have received renewed interest in the recent literature both in the open [4][5][6][7][8][9] (see also [10] for a recent review) as well as the closed string sector [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. In the case of closed string theories, a way to break supersymmetry spontaneously while retaining the perturbative world-sheet description is the stringy version [29][30][31][32] of the Scherk-Schwarz mechanism [33,34].…”

On nonsupersymmetric Pati-Salam string models

“…An important open problem in string phenomenology concerns the mechanism of spontaneous supersymmetry breaking and its physical consequences which has attracted considerable interest in recent literature [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. To this end, a tree-level analysis is insufficient for a quantitative comparison with low energy data, and the incorporation of quantum corrections to terms in the string effective action becomes a necessary yet daunting task.…”