arXiv subjects

Hermann Nicolai

Publications and source records attributed to Hermann Nicolai.

113 records · Page 7Linked to original sources

arXiv1998

On M-Theory

This contribution gives a personal view on recent attempts to find a unified framework for non-perturbative string theories, with special emphasis on the hidden symmetries of supergravity and their possible role in this endeavor. A reformulation of $d=11$ supergravity with enlarged tangent space symmetry SO(1,2) $\times$ SO(16) is discussed from this perspective, as well as an ansatz to construct yet further versions with SO(1,1) $\times$ SO(16)$^\infty$ and possibly even SO(1,1)$_+$ $\times$ ISO(16)$^\infty$ tangent space symmetry. It is suggested that upon ``third quantization'', dimensionally reduced maximal supergravity may have an equally important role to play in this unification as the dimensionally reduced maximally supersymmetric $SU(\infty)$ Yang Mills theory.

hep-th↗

arXiv1997

New Canonical Variables for d=11 Supergravity

A set of new canonical variables for $d=11$ supergravity is proposed which renders the supersymmetry variations and the supersymmetry constraint polynomial. The construction is based on the $SO(1,2)\times SO(16)$ invariant reformulation of $d=11$ supergravity given in previous work, and has some similarities with Ashtekar's reformulation of Einstein's theory. The new bosonic variables fuse the gravitational degrees of freedom with those of the three-index photon $A_{MNP}$ in accordance with the hidden symmetries of the dimensionally reduced theory. Although $E_8$ is not a symmetry of the theory, the bosonic sector exhibits a remarkable $E_8$ structure, hinting at the existence of a novel type of ``exceptional geometry''.

hep-th↗

arXiv1997

On the Imaginary Simple Roots of the Borcherds Algebra $g_{II_{9,1}}$

In a recent paper (hep-th/9703084) it was conjectured that the imaginary simple roots of the Borcherds algebra $g_{II_{9,1}}$ at level 1 are its only ones. We here propose an independent test of this conjecture, establishing its validity for all roots of norm $\geq -8$. However, the conjecture fails for roots of norm -10 and beyond, as we show by computing the simple multiplicities down to norm -24, which turn out to be remakably small in comparison with the corresponding $E_{10}$ multiplicities. Our derivation is based on a modified denominator formula combining the denominator formulas for $E_{10}$ and $g_{II_{9,1}}$, and provides an efficient method for determining the imaginary simple roots. In addition, we compute the $E_{10}$ multiplicities of all roots up to height 231, including levels up to $\ell =6$ and norms -42.

hep-th↗

arXiv1996

Seven Dimensional Octonionic Yang-Mills Instanton and its Extension to an Heterotic String Soliton

We construct an octonionic instanton solution to the seven dimensional Yang-Mills theory based on the exceptional gauge group $G_2$ which is the automorphism group of the division algebra of octonions. This octonionic instanton has an extension to a solitonic two-brane solution of the low energy effective theory of the heterotic string that preserves two of the sixteen supersymmetries and hence corresponds to $N=1$ space-time supersymmetry in the (2+1) dimensions transverse to the seven dimensions where the Yang-Mills instanton is defined.

hep-th↗

arXiv1993

On the Exact Operator Formalism of Two-Dimensional Liouville Quantum Gravity in Minkowski Spacetime

A detailed reexamination is made of the exact operator formalism of two-dimensional Liouville quantum gravity in Minkowski spacetime with the cosmological term fully taken into account. Making use of the canonical mapping from the interacting Liouville field into a free field, we focus on the problem of how the Liouville exponential operator should be properly defined. In particular, the condition of mutual locality among the exponential operators is carefully analyzed, and a new solution, which is neither smoothly connected nor relatively local to the existing solution, is found. Our analysis indicates that, in Minkowski spacetime, coupling gravity to matter with central charge $d<1$ is problematical. For $d=1$, our new solution appears to be the appropriate one; for this value of $d$, we demonstrate that the operator equation of motion is satisfied to all orders in the cosmological constant with a certain regularization. As an application of the formalism, an attempt is made to study how the basic generators of the ground ring get modified due to the inclusion of the cosmological term. Our investigation, although incomplete, suggests that in terms of the canonically mapped free field the ground ring is not modified.

hep-th↗