The Bosonic Ancestor of Closed and Open Fermionic Strings

We review the emergence of the ten-dimensional fermionic closed string theories from subspaces of the Hilbert space of the 26-dimensional bosonic closed string theory compactified on an $E_8\times SO(16)$ lattice. They arise from a consistent truncation procedure which generates space-time fermions out of bosons. This procedure is extended to open string sectors. We prove, from bosonic considerations alone, that truncation of the unique tadpole-free $SO(2^{13})$ bosonic string theory compactified on the above lattice determines the anomaly free Chan-Paton group of the Type I theory. It also yields the Chan-Paton groups making Type O theories tadpole-free. These results establish a link between all M-theory strings and the bosonic string within the framework of conformal field theory. Its significance is discussed.Comment: LaTeX files, 16 pages. Contribution to the Francqui meeting, Brussels 2001 and Corfu Summer Institute 2001. Based on hep-th/010623

Not doomed to fail

In their recent manuscript “An uplifting discussion of T-duality ” [26], J. Harvey and G. Moore have reevaluated a mod two condition appearing in asymmetric orbifold constructions as an obstruction to the description of certain symmetries of toroidal conformal field theories by means of automorphisms of the underlying charge lattice. The relevant “doomed to fail” condition determines whether or not such a lattice automorphism g may lift to a symmetry in the corresponding toroidal conformal field theory without introducing extra phases. If doomed to fail, then in some cases, the lift of g must have double the order of g. It is an interesting question, whether or not “geometric” symmetries are affected by these findings. In the present note, we answer this question in the negative, by means of elementary linear algebra: “geometric” symmetries of toroidal conformal field theories are not doomed to fail. Consequently, and in particular, the symmetry groups involved in symmetry surfing the moduli space of K3 theories do not differ from their lifts

Magnetic fields generated by submarine power cables have a negligible effect on the swimming behavior of Atlantic lumpfish (Cyclopterus lumpus) juveniles

Submarine power cables carry electricity over long distances. Their geographic distribution, number, and areal coverage are increasing rapidly with the development of, for example, offshore wind facilities. The flow of current passing through these cables creates a magnetic field (MF) that can potentially affect marine organisms, particularly those that are magnetosensitive. The lumpfish (Cyclopterus lumpus) is a migratory species that is widely distributed in the North Atlantic Ocean and Barents Sea. It migrates between coastal spawning grounds and pelagic offshore feeding areas. We tested whether lumpfish respond to MFs of the same intensity as those emitted by high voltage direct current (HVDC) submarine power cables. Laboratory experiments were conducted by placing juvenile lumpfish in an artificial MF gradient generated by a Helmholtz coil system. The intensity of the artificial MF used (230 µT) corresponded to the field at 1 m from a high-power submarine cable. The fish were filmed for 30 min with the coil either on or off. Swimming speeds, and presence in the different parts of a raceway, were extracted from the videos and analyzed. Juvenile lumpfish activity, defined as the time that the fish spent swimming relative to stationary pauses (attached to the substrate), and the distance travelled, were unaffected by exposure to the artificial MF. The swimming speed of juvenile lumpfish was reduced (by 16%) when the coil was on indicating that the fish could either sense the MF or the induced electric field created by the movement of the fish through the magnetic field. However, it seems unlikely that a 16% decrease in swimming speed occurring within 1 m of HVDC cables would significantly affect Atlantic lumpfish migration or homing.publishedVersio

Coset Construction and Character Sumrules for the Doubly Extended N=4N=4 Superconformal Algebras

Character sumrules associated with the realization of the $N=4$ superconformal algebra \At on manifolds corresponding to the group cosets SU(3)_{\ktp }/U(1) are derived and developed as an important tool in obtaining the modular properties of \At characters as well as information on certain extensions of that algebra. Their structure strongly suggests the existence of rational conformal field theories with central charges in the range $1 \le c\le 4$. The corresponding characters appear in the massive sector of the sumrules and are completely specified in terms of the characters for the parafermionic theory $SU(3)/(SU(2)\times U(1))$ and in terms of the branching functions of massless \At characters into SU(2)_{\ktp }\times SU(2)_1 characters.Comment: 31 pages, DTP/92/49 NBI-HE-92-73 (latex file