arXiv subjects

B. E. W. Nilsson

Publications and source records attributed to B. E. W. Nilsson.

6 recordsLinked to original sources

arXiv2025

Kaluza-Klein Supergravity 2025

We recall our work in the 1980s taking seriously the maximal eleven dimensions of supergravity, in particular the round, left squashed and right squashed $S^7$ compactifications to $D=4$ yielding $\mathcal N=8$, $\mathcal N=1$ and $\mathcal N=0$, respectively. This involved Kaluza-Kein techniques that have found wider applications such as spontaneous compactification, holonomy and supersymmetry, topology versus geometry, squashing and Higgs, vacuum stability and consistent truncations.

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arXiv2023

De-Higgsing In Eleven-Dimensional Supergravity On The Squashed $S^7$

In this paper we construct the subset of modes on $S^7$ that are relevant in the compactification of eleven-dimensional supergravity on a squashed $S^7$ when restricted to the sector that comprises singlets under the $Sp(1)\times Sp(2)$ isometry of the squashed sphere. Some of the properties of these modes, connected to the transition from the round $S^7$ to the squashed $S^7$, are analysed in detail. Special features of the Rarita-Schwinger operator, described in earlier work by Buchdahl, are explained and related to properties of the squashed $S^7$ operator spectrum obtained in previous work by the authors. We then discuss how the singlet modes give rise to supermultiplets in the left-squashed case, the phenomenon of de-Higgsing, and what happens to the AdS$_4$ fields in these supermultiplets under an orientation reversal (``skew-whiffing'') of the squashed $S^7$. Finally, we consider the possible choices of boundary conditions that appear for some of these fields in AdS$_4$ in the case of the right-squashed non-supersymmetric compactification, and how these choices may affect the stability of the gravity theory.

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arXiv2019

The role of singletons in $S^7$ compactifications

We derive the isometry irrep content of squashed seven-sphere compactifications of eleven-dimensional supergravity, i.e., the left-squashed ($LS^7$) with ${\mathcal N}=1$ and right-squashed ($RS^7$) with ${\mathcal N}=0$ supersymmetry, in a manner completely independent of the round sphere. Then we compare this result with the spectrum obtained by Higgsing the round sphere spectrum. This way we discover features of the spectra which makes it possible to argue that the only way the round spectrum can be related by a Higgs mechanism to the one of $LS^7$ is if the singletons are included in the round sphere spectrum. For this to work also in the $RS^7$ case it seems that the gravitino of the $LS^7$ spectrum must be replaced by a fermionic singleton present in the $RS^7$ spectrum.

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arXiv1997

The Multivalued Free-Field Maps of Liouville and Toda Gravities

Liouville and Toda gravity theories with non-vanishing interaction potentials have spectra obtained by dividing the free-field spectra for these cases by the Weyl group of the corresponding $A_1$ or $A_2$ Lie algebra. We study the canonical transformations between interacting and free fields using the technique of intertwining operators, giving explicit constructions for the wavefunctions and showing that they are invariant under the corresponding Weyl groups. These explicit constructions also permit a detailed analysis of the operator-state maps and of the nature of the Seiberg bounds.

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arXiv1994

Higher-Dimensional Loop Algebras, Non-Abelian Extensions and p-Branes

We postulate a new type of operator algebra with a non-abelian extension. This algebra generalizes the Kac--Moody algebra in string theory and the Mickelsson--Faddeev algebra in three dimensions to higher-dimensional extended objects ($p$-branes). We then construct new BRST operators, covariant derivatives and curvature tensors in the higher-dimensional generalization of loop space.

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arXiv1992

The Low-level Spectrum of the $W_3$ String

We investigate the spectrum of physical states in the $W_3$ string theory, up to level 2 for a multi-scalar string, and up to level 4 for the two-scalar string. The (open) $W_3$ string has a photon as its only massless state. By using screening charges to study the null physical states in the two-scalar $W_3$ string, we are able to learn about the gauge symmetries of the states in the multi-scalar $W_3$ string.

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