Supergravity Research Articles

Massive ambitwistor-strings; twistorial models

Ambitwistor-strings are chiral strings whose targets are spaces of complex massless particles, and whose correlation functions directly lead to simple, compact formulae for scattering amplitudes and loop integrands for massless gauge and gravity theories. This article extends the framework to massive particles in 4d, obtained via a symmetry reduction of higher dimensional massless models based on twistors. The target space of the resulting models turns out to be the phase space of 4d massive particles in a twistorial representation, and the worldsheet theory agrees with the two-twistor string previously introduced by the authors. The paper has been written so as to be largely self-contained. We discuss two interesting classes of massive theories in detail. For gauge theories, the reduction procedure is explicitly adapted to supersymmetric gauge theories on the Coulomb branch. For supergravity theories, the reduction is adapted to give theories obtained via Cremmer, Scherk & Schwartz (CSS) reduction, with broken supersymmetry and massive multiplets. The reduction procedure gives explicit and systematic rules to obtain amplitudes for all these theories and their amplitudes from two compact master formulae that have their origins in 6d based on the polarized scattering equations; in the CSS case the formulae are new, and in both cases their derivation is systematic. The freedom to include mass allows the definition of a loop insertion operator, thereby extending the formulae to 1-loop. Unlike the massless 4d twistorial models, these all display a perfect double copy structure, here incorporating massive particles in the relationship between gauge theory and CSS supergravity amplitudes.

2-term averaging L∞-algebras and non-abelian extensions of averaging Lie algebras

In recent years, averaging operators on Lie algebras (also called embedding tensors in the physics literature) and associated tensor hierarchies have formed an efficient tool for constructing supergravity and higher gauge theories. A Lie algebra with an averaging operator is called an averaging Lie algebra. In the present paper, we introduce 2-term averaging L∞-algebras and give characterizations of some particular classes of such homotopy algebras. Next, we study non-abelian extensions of an averaging Lie algebra by another averaging Lie algebra. We define the second non-abelian cohomology group to classify the equivalence classes of such non-abelian extensions. Next, given a non-abelian extension of averaging Lie algebras, we show that the obstruction for a pair of averaging Lie algebra automorphisms to be inducible can be seen as the image of a suitable Wells map. Finally, we discuss the Wells short exact sequence in the above context.

Stable non-BPS black holes and black strings in five dimensions

In this paper we study black hole and black string solutions in five dimensional N=2 supergravity theories arising from the compactification of M-theory on Calabi-Yau manifolds. In particular, we consider explicit examples of three parameter Calabi-Yau manifolds which are obtained as hypersurfaces in toric varieties. Using the attractor mechanism, we obtain Bogomol’nyi-Prasad-Sommerfield (BPS) as well as non-BPS black holes in these compactified supergravity theories. We also consider the black string solutions in these models. We analyze the stability of these extremal black brane configurations by computing the recombination factor. We find multiple stable non-BPS attractor solutions in some of these models. Published by the American Physical Society 2024

Super Gravity and Wormhole Hole Entanglement Heuristics in Blackhole and Whitehole Cosmology

Super Gravity and Wormhole Hole Entanglement Heuristics in Blackhole and Whitehole Cosmology

DS2 supergravity

We construct two-dimensional supergravity theories endowed with a positive cosmological constant, that admit de Sitter vacua. We consider the cases of N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 1 as well as N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 2 supersymmetry, and couple the supergravity to a superconformal field theory with the same amount of supersymmetry. Upon fixing a supersymmetric extension of the Weyl gauge, the theories are captured, at the quantum level, by supersymmetric extensions of timelike Liouville theory with N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 1 and N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 2 supersymmetry respectively. The theories exhibit good ultraviolet properties and are amenable to a variety of techniques such as systematic loop expansions and, in the N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 2 case, supersymmetric localization. Our constructions offer a novel path toward a precise treatment of the Euclidean gravitational path integral for de Sitter, and in turn, the Gibbons-Hawking entropy of the de Sitter horizon. We argue that the supersymmetric localization method applied to the N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 2 theory must receive contributions from boundary terms in configuration space. We also discuss how these theories overcome several obstructions that appear upon combining de Sitter space with supersymmetry.

Non-Lorentzian Jackiw–Teitelboim supergravity

We will review the non-Lorentzian (nonrelativistic and ultrarelativistic) Jackiw–Teitelboim supergravity theories, which are the limits of relativistic Jackiw–Teitelboim supergravity. The construction is based on BF theory formalism and also the extended Newton–Hooke and extended AdS Carroll superalgebras in two space–time dimensions. It is also shown that nonrelativistic and ultrarelativistic supergravity actions are related to each other by a map which is shown explicitly in this review. This is supersymmetric version of Galilei/Carroll duality in two dimensions.

Melvin space-times in supergravity

We consider Melvin-like cosmological and static solutions for the theories of N=2, D=4 supergravity coupled to vector multiplets. We analyze the equations of motion and give some explicit solutions with one scalar and two gauge fields. Generalized Melvin solutions with four charges are also constructed for an embedding of a truncated N=8 supergravity theory. Our results are then extended to supergravity theories with the scalar manifolds SL(N,R)/SO(N,R). It is shown that solutions with N charges only exist for N=8, 6 and 5 corresponding to theories with space-time dimensions D=4, 5 and 7.

Supersymmetric AdS Solitons, Ground States, and Phase Transitions in Maximal Gauged Supergravity

We review some recent soliton solutions in a class of four-dimensional supergravity theories. The latter can be obtained from black hole solutions by means of a double Wick rotation. For special values of the parameters, the new configurations can be embedded in the gauged maximal N=8 theory and uplifted in the higher-dimensional D=11 theory. We also consider BPS soliton solutions, preserving a certain fraction of supersymmetry.

Hazard and Removal of Soluble Sodium from Red Mud Through Stepwise Recovery by Super Gravity

Hazard and Removal of Soluble Sodium from Red Mud Through Stepwise Recovery by Super Gravity

Compactifying the Kerr-Schild double copy

We show that the classical double copy relationship for Kerr-Schild spacetimes can be dimensionally reduced to give a natural notion of the double copy for Kaluza-Klein theory with gravity coupled to a gauge field and a dilaton. Under dimensional reduction the Kerr-Schild (KS) ansatz becomes the stringy Kerr-Schild (sKS) ansatz introduced by Wu. This ansatz captures many Kaluza-Klein black hole solutions, including single-charge black holes arising in both gauged and ungauged supergravity theories. We identify the single copy gauge field and scalar field of an arbitrary sKS solution. We show that the boost-reduction procedure for generating charged black hole solutions can be generalized to any stationary KS seed, and used to combine the metric with the zeroth and single copies of that seed into a single sKS solution. Furthermore, we comment on multi-charge solutions that can be written in a multi-sKS form, proposing a double copy interpretation involving multiple single copy sectors.

Green and Efficient Pre-concentration of Niobium From Low-Grade Niobite via Super Gravity

Green and Efficient Pre-concentration of Niobium From Low-Grade Niobite via Super Gravity

Refining mechanism and elevated-temperature mechanical properties of Al-Ce alloys solidified under super gravity field

We reported that the enhanced elevated-temperature mechanical property of Al-Ce alloy could be obtained by solidification under super-gravity field. The refinement of eutectic Al11Ce3 is detected, which can be ascribe to the enhancement of mass transfer under super-gravity field, affecting the nucleation rate and inhibiting the growth of eutectic phase for this irregular Al-Ce eutectic system. Interestingly, the refined eutectic Al11Ce3 is thermally stable even up to 400 °C thermal exposure without obvious coarsening, contributing to the enhancement of elevated-temperature mechanical properties (∼125.0 ± 9.1 MPa at 300 °C), which is ∼74.8% higher than that solidified under normal gravity field (∼71.5 ± 0.6 MPa). The refinement of eutectic Al11Ce3 with higher number density also contribute to the stress dispersion, the crack prefer to propagate through the eutectic colony, leading to the transformation of fracture mode from brittle to ductile.

Interpreting the cosmic history of the Universe through five-dimensional supergravity

Through modeling the Universe as a symplectic 3-brane embedded in the bulk of five-dimensional ungauged supergravity theory, the entire evolution of the Universe can be interpreted from inflation to late-time acceleration without introducing an inflaton nor a cosmological constant. The time dependence of the brane is strongly correlated to the complex structure moduli of the underlying Calabi–Yau submanifold and the bulk effects. The solutions to the field equations are found by exploiting the theory’s symplectic structure where the time evolution is similar to our Universe according to the latest data of the Planck mission. Our results present a new explanation for the nature of dark energy mainly based on the topology of the subspace and the existence of a fifth extra dimension.

Combined constraints on dark photons and discovery prospects at the LHC and the Forward Physics Facility

Hidden sectors are ubiquitous in supergravity theories, in strings and in branes. Well motivated models such as the Stueckelberg hidden sector model could provide a candidate for dark matter. In such models, the hidden sector communicates with the visible sector via the exchange of a dark photon (dark Z′) while dark matter is constituted of Dirac fermions in the hidden sector. Using data from collider searches and precision measurements of SM processes as well as the most recent limits from dark matter direct and indirect detection experiments, we perform a comprehensive scan over a wide range of the Z′ mass and set exclusion bounds on the parameter space from sub-GeV to several TeV. We then discuss the discovery potential of an mathcal{O} (TeV) scale Z′ at HL-LHC and the ability of future forward detectors to probe very weakly interacting sub-GeV Z′ bosons. Our analysis shows that the parameter space in which a Z′ can decay to hidden sector dark matter is severely constrained whereas limits become much weaker for a Z′ with no dark decays. The analysis also favors a self-thermalized dark sector which is necessary to satisfy the dark matter relic density.

Quantum gravity bounds on mathcal{N} = 1 effective theories in four dimensions

We propose quantum gravitational constraints on effective four-dimensional theories with mathcal{N} = 1 supersymmetry. These Swampland constraints arise by demanding consistency of the worldsheet theory of a class of axionic, or EFT, strings whose existence follows from the Completeness Conjecture of quantum gravity. Modulo certain assumptions, we derive positivity bounds and quantization conditions for the axionic couplings to the gauge and gravitational sector at the two- and four-derivative level, respectively. We furthermore obtain general bounds on the rank of the gauge sector in terms of the gravitational couplings to the axions. We exemplify how these bounds rule out otherwise consistent effective supergravity theories as theories of quantum gravity. Our derivations of the quantum gravity bounds are tested and further motivated in concrete string theoretic settings. In particular, this leads to a sharper version of the bound on the gauge group rank in F-theory on elliptic four-folds with a smooth base, which improves the known geometrical Kodaira bounds. We furthermore provide a detailed derivation of the EFT string constraints in heterotic string compactifications including higher derivative corrections to the effective action and apply the bounds to M-theory compactifications on G2 manifolds.

Linearizing the BPS equations with vector and tensor multiplets

We analyse the BPS equations of mathcal{N} = (1, 0) supergravity theory in six dimensions coupled to a vector and tensor multiplet. We show how these BPS equations can be reduced to a set of linear differential equations. This system is triangular in that each layer of equations, while linear, is quadratically sourced by the solutions of the previous layers. We examine several explicit examples and discuss the construction of new families of microstate geometries. We expect that the result presented here will open up new branches of superstrata in which the momentum is encoded in a new class of charge carriers.

The desert and the swampland

The most natural expectation away from asymptotic limits in moduli space of supergravity theories is the desert scenario, where there are few states between massless fields and the quantum gravity cutoff. In this paper we initiate a systematic study of these regions deep in the moduli space, and use it to place a bound on the number of massless modes by relating it to the black hole species problem. There exists a consistent sub-Planckian UV cutoff (the species scale) which resolves the black hole species problem without bounding the number of light modes. We reevaluate this in the context of supersymmetric string vacua in the desert region and show that even though heuristically the species scale is compatible with expectations, the BPS states of the actual string vacua lead to a stronger dependence of the cutoff scale on the number of massless modes. We propose that this discrepancy, which can be captured by the “BPS desert conjecture”, resurrects the idea of a uniform bound on the number of light modes as a way to avoid the black hole species problem. This conjecture also implies a stronger form of the Tadpole Conjecture, which leads to an obstruction in stabilizing all moduli semi-classically for large number of moduli in flux compactifications.

Separation of niobium and rare earths from Fe-Nb-RE associated ultra-low-grade tailings using super gravity

Bayan Obo tailings is unique polymetallic resource associated with iron, niobium (Nb) and rare earths (REEs). However, conventional extraction processes are not economically viable for Nb and REEs due to their low-grade nature. To overcome this challenge, a new approach was employed in this study. The Fe-Nb-RE associated tailings were first reduced and iron-slag was separated at low temperatures under super gravity. This process transformed Nb and REEs into a Nb/REEs-rich phase in the primary enriched slag, which was then separated from the slag by super gravity to obtain a high-grade enriched sample. The end result was a sample with Nb2O5 and RE2O3 mass fractions of up to 24.98 wt% and 30.01 wt%, respectively. This process successfully concentrated Nb and REEs from associated elemental impurities and gangue minerals in the Fe-Nb-RE associated ultra-low-grade tailings, making extraction easier, optimizing subsequent leaching/dissolution, and reducing the number of steps and material flows required in the downstream hydrometallurgical extraction.

Study of tunneling radiation and thermal fluctuations of a gauge super gravity like black hole

The Newman–Janis technique and the semi-classical Hamilton–Jacobi approach are two distinct phenomena that we apply in this paper to examine the Hawking temperature (TH) for 4-dimensional gauge super gravity like black hole with rotation parameters. First, using the Newman–Janis algorithmic approach, we compute the gauge super gravity like black holes solution. We use surface gravity to derive the TH for a gauge super gravity like black hole. In order to do this, we use the Lagrangian field equation in the background of generalized uncertainty principle, semi-classical Hamilton–Jacobi approach and the WKB approximation technique. Furthermore, we investigate the stability of considered geometry with the help of corrected entropy and well known thermodynamic quantities. It is concluded that the gauge super gravity like black holes is stable under first-order corrections.

Mass spectrum of type IIB flux compactifications — comments on AdS vacua and conformal dimensions

In this note we study the mass spectrum of type IIB flux compactifications. We first give a general discussion of the mass matrix for F-term vacua in four-dimensional mathcal{N} = 1 supergravity theories and then specialize to type IIB Calabi-Yau orientifold compactifications in the presence of geometric and non-geometric fluxes. F-term vacua in this setting are in general AdS4 vacua for which we compute the conformal dimensions of operators dual to the scalar fields. For the mirror-dual of the DGKT construction we find that one-loop corrections to the complex-structure moduli space lead to real-valued conformal dimensions — only when ignoring these corrections we recover the integer values previously reported in the literature. For an example of a flux configurations more general than the DGKT mirror we also obtain non-integer conformal dimensions. Furthermore, we argue that stabilizing the axio-dilaton and complex-structure moduli in asymptotic regions of moduli space by fluxes implies that at least one of the corresponding mass eigenvalues diverges.