Narrow Results

In light of NANOGrav data, we provide for the first time possible observational signatures of Superstring theory. First, we work with inflection-point inflationary potentials naturally realized within Wess–Zumino-type no-scale Supergravity, which give rise to the formation of microscopic primordial black holes (PBHs) triggering an early matter-dominated era (eMD) and evaporating before big bang nucleosynthesis (BBN). Remarkably, we obtain an abundant production of primordial gravitational waves (PGW) at the frequency ranges of nHz, Hz and kHz and in strong agreement with pulsar time array (PTA) gravitational wave (GW) data. This PGW background could serve as a compelling observational signature for the presence of quantum gravity via no-scale Supergravity.

In this paper, we consider the single-parameter $\mathcal{ℛ}+c{\mathcal{ℛ}}^2$ gravitational action and use constraints from astrophysics and the laboratory to derive a natural relation between the coefficient c and the value of the cosmological constant. We find that the renormalization of c from the energy of the inflationary phase to the infrared, where the acceleration of the expansion of the universe takes place, is correlated with the evolution of the vacuum energy. Our results suggest that the coefficient of the ${\mathcal{ℛ}}^2$ term may provide an unexpected bridge between high-energy physics and cosmological phenomena such as inflation and dark energy.

We study some of the properties of the geometry of the exceptional Lie group E₇₍₇₎, which describes the U-duality of the , d = 4 supergravity. In particular, based on a symplectic construction of the Lie algebra 𝔢₇₍₇₎ due to Adams, we compute the Iwasawa decomposition of the symmetric space , which gives the vector multiplets' scalar manifold of the corresponding supergravity theory.

The explicit expression of the Lie algebra is then used to analyze the origin of as scalar configuration of the "large" ⅛-BPS extremal black hole attractors. In this framework it turns out that the U(1) symmetry spanning such attractors is broken down to a discrete subgroup ℤ₄, spoiling their dyonic nature near the origin of the scalar manifold.

This is a consequence of the fact that the maximal manifest off-shell symmetry of the Iwasawa parametrization is determined by a completely non-compact Cartan subalgebra of the maximal subgroup SL(8, ℝ) of E₇₍₇₎, which breaks down the maximal possible covariance SL(8, ℝ) to a smaller SL(7, ℝ) subgroup. These results are compared with the ones obtained in other known bases, such as the Sezgin-van Nieuwenhuizen and the Cremmer-Julia /de Wit-Nicolai frames.

Killing–Yano symmetry has played an important role in the study of black hole physics. In supergravity theories, Killing–Yano symmetry is deformed by the presence of the fluxes which can be identified with skew-symmetric torsion. Therefore, we attempt to classify spacetimes admitting Killing-Yano symmetry with torsion. In particular, the classification problem of metrics admitting a principal Killing–Yano tensor with torsion is discussed.

In this talk, we review the construction of two three-dimensional non-relativistic pure supergravity theories. One of these yields a supersymmetrization of Newton-Cartan gravity. The other one is a Chern-Simons theory with different bosonic equations of motion and matter couplings than Newton-Cartan gravity. We comment on the prospect of using these theories to construct non-relativistic supersymmetric field theories in curved backgrounds, that can be amenable to exact non-perturbative analysis via localization techniques.

The following sections are included:

• Introduction
• Ansatz, asymptotic behavior and charges
• Magnetized and squashed configurations
• Supersymmetric solutions
• Conclusions
• Acknowledgments
• References

Double field theory promotes the T-duality of closed string theory to a manifest symmetry, thus leading to a new perspective on the geometry experienced by stringy probes. In this contribution, we discuss the mathematical structure underlying the symmetries of double field theory, thus defining a DFT algebroid. We trace its origins in a large Courant algebroid defined over a doubled geometry, and show that after imposing a section condition the DFT algebroid reduces to a canonical Courant algebroid, as expected in generalized geometry.

Theories with elementary scalar degrees of freedom seem nowadays required for simple descriptions of the Standard Model and of the Early Universe. It is then natural to embed theories of inflation in supergravity, also in view of their possible ultraviolet completion in String Theory. After some general remarks on inflation in supergravity, we describe examples of minimal inflaton dynamics which are compatible with recent observations, including higher-curvature ones inspired by the Starobinsky model. We also discuss different scenarios for supersymmetry breaking during and after inflation, which include a revived role for non-linear realizations. In this spirit, we conclude with a discussion of the link, in four dimensions, between “brane supersymmetry breaking” and the super-Higgs effect in supergravity.

The plethora of recent and forthcoming data on the cosmic microwave background (CMB) data are stimulating a new wave of inflationary model-building. Naturalness suggests that the appropriate framework for models of inflation is supersymmetry. This should be combined with gravity in a supergravity theory, whose specific no-scale version has much to commend it, e.g. its derivation from string theory and the flat directions in its effective potential. Simple no-scale supergravity models yield predictions similar to those of the Starobinsky R + R² model, though some string-motivated versions make alternative predictions. Data are beginning to provide interesting constraints on the rate of inflaton decay into Standard Model particles. In parallel, LHC and other data provide significant constraints on no-scale supergravity models, which suggest that some sparticles might have masses close to present experimental limits.

This work summarises recent progress obtained by the mini-superpspace quantization of N = 1, d = 4 supergravity, formulated in the framework of the Bianchi IX cosmological model. The emphasis is put on three main results: the completeness of the solution space obtained, the elements suggesting a hidden Kac-Moody structure of the theory and those leading to conjecture an avoidance of the cosmological singularity by some branches of the wave function of the Universe.

We consider the construction of a transgression field theory invariant under the Poincare supergroup ${\mathcal{P}}_5$, modulo boundary terms. The transgression action is constructed from the lagrangian for five dimensional Chern–Simons supergravity through the introduction of two 1-forms gauge connections valuated in the corresponding Lie superalgebra. These conections are associated to linear and nonlinear realizations of the Poincaré supergroup. From a dimensional reduction of the transgression field theory we get a four dimensional gauged Wess–Zumino–Witten action whose fields are the original gauge fields of the Chern–Simons theory plus the set of tensorial and spinorials functions relating the gauge conections corresponding to the parameterized coordinates of the coset space ${\mathcal{P}}_5/SO(1,4)$ in the adjoint representation. The resulting action and its equations of motion are studied.

In this paper we present a model for accelerated expansion of the universe, both during inflation and the present stage of the expansion, from four dimensional 𝒩 = 1 supergravity. We evaluate the tensor-to-scalar ratio (r ≈ 0.00034), the scalar spectral index (n_s ≈ 0.970) and the running spetral index (dn_s/dk ≈ −6 × 10⁻⁵), and we notice that these parameters are in agreement with Planck+WP+lensing data and with BICEP2/Keck and Planck joint analysis, at 95% CL. The number of e-folds is 50 or higher. The reheating period has an associated temperature T_R ˜ 10¹² GeV, which agrees with the one required by thermal leptogenesis. Regarding the scalar field as dark energy, the autonomous system for it in the presence of a barotropic fluid provides a stable fixed point that leads to a late-time accelerated expansion of the universe, with an equation of state that mimics the cosmological constant (ω_Φ ≈ −0.997).

Klein-Gordon equation is the starting point of the scattering and gauge/gravity calculations for black holes. Thus, studying its separability and probing the residua associated with the black hole horizons are key issues that constitute the core of the calculations for the black hole internal structure. One can write the radial part of the Klein-Gordon equation in a specific form that reveals the pole structure of the horizon equation. The residua of the poles reflect the physical properties, namely surface gravities and angular velocities associated with respective horizons. We start with the Kerr black hole by showing the correspondence of the residua of the poles and the monodromy exponents. Then we study the cases of the most general nonextremal black hole solutions in four and five dimensional gauged supergravity.

After a brief discussion of RR and NS fluxes, we consider the T-duality family of fluxes whose prototype is the Scherk-Schwarz reduction of the S-dual of the RR scalar of IIB supergravity. We give a complete classification of these fluxes, including the ones that are non-geometric, and we explain their relation with dual mixed-symmetry potentials. We point out that the non-geometric fluxes turn out to be dual to potentials containing nine antisymmetric indices. Our analysis suggests that all these fluxes can be understood in the context of double field theory, although for the non-geometric ones one expects a violation of the strong constraint.

We define an algebraic characterization of half supersymmetric branes in supergravity theories with different amount of supersymmetry. We furthermore illustrate how this classification can be used as starting point to explain the orbits stratification for extremal black holes.

We discuss the construction and basic properties of a recently constructed 𝒩 = 1 supergravity theory in 4 dimensions with spontaneously broken local supersymmetry, called ‘de Sitter supergravity’. The theory has a cosmological constant that can be positive, zero or negative. Nilpotent multiplets and non-linear Volkov-Akulov supersymmetry play an important role in the construction. We shortly discuss some recent extensions of the theory.

We study inflation in the α−attractor model under a non-slow-roll dynamics with an ansatz proposed by Gong & Sasaki of assuming N = N (ϕ). Under this approach, we construct a class of local shapes of inflaton potential that are different from the T-models. We find this type of inflationary scenario predicts an attractor at n_s ∼ 0.967 and r ∼ 0.00055. In our approach, the non-slow-roll inflaton dynamics are related to the α−parameter which is the curvature of Kähler geometry in the SUGRA embedding of this model.

We describe how the known two-dimensional integrable ansatz in pure gravity can be extended to the N = 2 supergravity model.