On a theorem of Garza regarding algebraic numbers with real conjugates
We give a new and simple proof of a theorem of Garza estimating the height (or Mahler measure) of an algebraic number with real conjugates.
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arXiv subjects
Gerald Höhn
Publications and source records attributed to Gerald Höhn.
Selbstduale Vertexoperatorsuperalgebren und das Babymonster (Self-dual Vertex Operator Super Algebras and the Baby Monster)
We investigate self-dual vertex operator algebras (VOAs) and super algebras (SVOAs). Using the genus one correlation functions, it is shown that self-dual SVOAs exist only for half-integral central charges. It is described how self-dual SVOAs can be constructed from self-dual VOAs of larger central charge. The analogy with integral lattices and binary codes is emphasized. One main result is the construction of the shorter Moonshine module, a self-dual SVOA of central charge 23.5 on which the Baby monster - the second largest sporadic simple group - acts by automorphisms. The shorter Moonshine module has the character q^(-47/48)*(1+ 4371q^(3/2)+ 96256q^2+ 1143745q^(5/2) +...) and is the "shorter cousin" of the Moonshine module. Its lattice and code analog are the shorter Leech lattice and shorter Golay code. We conjecture that the shorter Moonshine module is the unique SVOA with this character. The final chapter introduces the notion of extremal VOAs and SVOAs. These are self-dual (S)VOAs with character having the same first few coefficients as the vacuum representation of the Virasoro algebra of the same central charge. We show that extremal VOAs exist at least for the central charges 8, 16, 24, 32, 40 and that extremal SVOAs exist only for the central charges c=0.5, 1, ..., 7.5, 8, 12, 14, 15, 15.5, 23.5 and 24. Examples for c=24 (resp. 23.5) are the (shorter) Moonshine module. Again, our results are similar to results known for codes and lattices.
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Komplexe elliptische Geschlechter und S^1-aequivariante Kobordismustheorie (Complex elliptic genera and S^1-equivariant cobordism theory)
We introduce the universal complex elliptic genus phi_ell as the ring homomorphism from the complex cobordism ring Omega^U to the polynomial ring C[A,B,C,D] associated to the characteristic power series Q(x)=x/f(x), where f is the solution of the differential equation (f'/f)'=S(f'/f), S(y) = (y+A/2)^4-B/4*(y+A/2)^2+4C*(y+A/2)+B^2/64-2D. Formally, phi_ell arises as the index of the Dolbeault operator of the loop space of a manifold. For manifolds with vanishing first Chern class, phi_ell becomes a Jacobi form F(z,τ) for the full Jacobi group Z^2 x PSL_2(Z). We prove the rigidity of phi_ell for S^1-actions on SU-manifolds. The kernel of phi_ell in the rational SU-cobordism ring is characterized as the ideal generated by manifolds with S^1-action of fixed type t (an integer) different from 0. For z to be an N-division point on the elliptic curve determined by τ, phi_ell specializes to the Level N genus phi_N. We introduce the cobordism ring Omega^{U,N} of stably almost complex manifolds with first Chern class divisible by N and characterize the kernel of phi_N by certain ideals in the rationalized ring Omega^{U,N}. In Chapter 1, we construct a base sequence W_1, W_2, W_3, ... of the rational cobordism ring Omega^U on which phi_ell has the values A, B, C, D, and 0 for W_i with i>=5. In Chapter 2, phi_ell and phi_N are investigated and the main results are proven. Chapter 3 contains the further result that the level N genus is invariant under the blow up along a submanifold Y of a complex manifold X if the codimension of Y in X is congruent 1 modulo N.
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Virasoro frames and their Stabilizers for the E_8 lattice type Vertex Operator Algebra
The concept of a framed vertex operator algebra was studied in [DGH] (q-alg/9707008). This article is an analysis of all Virasoro frame stabilizers of the lattice VOA V for the E_8 root lattice, which is isomorphic to the E_8-level 1 affine Kac-Moody VOA V. We analyze the frame stabilizers, both as abstract groups and as subgroups of the Lie group Aut(V) = E_8(C). Each frame stabilizer is a finite group, contained in the normalizer of a 2B-pure elementary abelian 2-group in Aut(V). In particular, we prove that there are exactly five orbits for the action of Aut(V) on the set of Virasoro frames, settling an open question about V in Section 5 of [DGH]. The results about the group structure of the frame stabilizers can be stated purely in terms of modular braided tensor categories. Appendices present aspects of the theory of automorphism groups of VOAs. In particular, there is a result of general interest, on equivariant embeddings of lattices: embeddings of lattices into unimodular lattices which respect automorphism groups and definiteness. [DGH] C. Dong, R. Griess and G. Hoehn: "Framed vertex operator algebras, codes and the moonshine module", Comm. Math. Phys. 193 (1998), 407-448.
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Self-dual Codes over the Kleinian Four Group
We introduce self-dual codes over the Kleinian four group $K = \mathbb{Z}_2 \times \mathbb{Z}_2$ for a natural quadratic form on $K^n$ and develop the theory. Topics studied are: weight enumerators, mass formulas, classification up to length 8, neighbourhood graphs, extremal codes, shadows, generalized t-designs, lexicographic codes, the Hexacode and its odd and shorter cousin, automorphism groups, marked codes. Kleinian codes form a new and natural fourth step in a series of analogies between binary codes, lattices and vertex operator algebras. This analogy will be emphasized and explained in detail.
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