GUT precursors and entwined SUSY: The phenomenology of stable nonsupersymmetric strings

Abstract

Recent work has established a method of constructing nonsupersymmetric string models that are stable, with near-vanishing one-loop dilaton tadpoles and cosmological constants. This opens up the tantalizing possibility of realizing stable string models whose low-energy limits directly resemble the Standard Model rather than one of its supersymmetric extensions. In this paper we consider the general structure of such strings and find that they share two important phenomenological properties. The first is a so-called "GUT-precursor" structure in which new GUT-like states appear with masses that can be many orders of magnitude lighter than the scale of gauge coupling unification. These states allow a parametrically large compactification volume, even in weakly coupled heterotic strings, and in certain regions of parameter space can give rise to dramatic collider signatures which serve as "smoking guns" for this overall string framework. The second is a residual "entwined-SUSY" (or e-SUSY) structure for the matter multiplets in which different multiplet components carry different horizontal Uð1Þ charges. As a concrete example and existence proof of these features, we present a heterotic string model that contains the fundamental building blocks of the Standard Model such as the Standard-Model gauge group, complete chiral generations, and Higgs fields-all without supersymmetry. Even though massless gravitinos and gauginos are absent from the spectrum, we confirm that this model has an exponentially suppressed one-loop dilaton tadpole and displays both the GUT-precursor and e-SUSY structures. We also discuss some general phenomenological properties of e-SUSY, such as cancellations in radiative corrections to scalar masses, the possible existence of a corresponding approximate moduli space, and the prevention of rapid proton decay.

de Sitter in non-supersymmetric string theories: no-go theorems and brane-worlds

“…This result garners non-trivial evidence for the de Sitter conjecture and for the TCC in top-down nonsupersymmetric settings. It would be interesting to further investigate additional Swampland conjectures within a non-supersymmetric context and the resulting constraints on non-supersymmetric string phenomenology [128][129][130]. Here we have pointed out possible realizations of the 'distance conjecture', identifying Kaluza-Klein states as the relevant tower of states that become massless at infinite distance in field space.…”

Heterotic − type I dual pairs, rigid branes and broken SUSY

“…[14] models with spontaneously broken supersymmetry and dynamical stabilization of moduli at self-dual radii in AdS vacua were already considered. 2 In our conventions, all dimensionfull quantities are expressed in string units, with α set to 1. degenerate spectra (n F = n B ), should be considered [26][27][28][29][30][31][32]. 3 Alternatively, one can deal with Friedmann-Lemaître-Robertson-Walker flat cosmological evolutions, where the supersymmetry breaking scale [33][34][35] and possibly the finite temperature of the Universe [36][37][38][39][40][41][42] are time-dependent.…”

Moduli stability in type I string orbifold models

“…This is done by developing a global geometric picture of the potential, first described in [2,3] in the case of N = 4 → N = 0 models. The general route of breaking supersymmetry at the classical level in flat space, and analyzing the induced effective potential, was advocated in Refs [4,5,6,7,8,9,10,11,12,13,14]. Moreover, the question of stability was addressed in the heterotic string framework in [6,7,15,16,17,18,19].…”