Supersymmetric field theory with benign ghosts

We construct a supersymmetric (1+1)-dimensional field theory involving extra derivatives and associated ghosts: the spectrum of the Hamiltonian is not bounded from below, neither from above. In spite of that, there is neither classical, nor quantum collapse and unitarity is preserved.Comment: Final version published in J.Phys. A; 8 pages, 3 figure

6D superconformal theory as the theory of everything

We argue that the fundamental Theory of Everything is a conventional field theory defined in the flat multidimensional bulk. Our Universe should be obtained as a 3-brane classical solution in this theory. The renormalizability of the fundamental theory implies that it involves higher derivatives (HD). It should be supersymmetric (otherwise one cannot get rid of the huge induced cosmological term) and probably conformal (otherwise one can hardly cope with the problem of ghosts) . We present arguments that in conformal HD theories the ghosts (which are inherent for HD theories) might be not so malignant. In particular, we present a nontrivial QM HD model where ghosts are absent and the spectrum has a well defined ground state. The requirement of superconformal invariance restricts the dimension of the bulk to be D < 7. We suggest that the TOE lives in six dimensions and enjoys the maximum N = (2,0) superconformal symmetry. Unfortunately, no renormalizable field theory with this symmetry is presently known. We construct and discuss an N = (1,0) 6D supersymmetric gauge theory with four derivatives in the action. This theory involves a dimensionless coupling constant and is renormalizable. At the tree level, the theory enjoys conformal symmetry, but the latter is broken by quantum anomaly. The sign of the beta function corresponds to the Landau zero situation.Comment: 15 pages, 2 figures, based on the talks in Gribov-75 memorial workshop (Budapest, May 22-24) and the workshop "Supersymmetry and quantum symmetries" (Dubna, July 27-31

Multidimensional Dirac strings and the Witten index of SYMCS theories with groups of higher rank

We discuss generalized Dirac strings associated with a given Lie group. They live in r-dimensional complex space (r being the rank of the group). Such strings show up in the effective Born-Oppenheimer Hamiltonian for 3d supersymmetric Yang-Mills-Chern-Simons theories, brought up by the gluon loops. We calculate accurately the number of the vacuum states in the effective Hamiltonian associated with these strings. We also show that these states are irrelevant for the final SYMCS vacuum counting. The Witten index of SYMCS theories depends thus only on the strings generated by fermion loops and carrying fractional generalized fluxes.Comment: 34 pages, 4 figure

Witten index in N=1 and N=2 SYMCS theories with matter

We calculate the Witten index for 3d supersymmetric Yang-Mills-Chern-Simons theories with matter. For N=2 theories, our results coincide with the results of recent [1]. We compare the situation in 3d to that in 4d N = 1 theories with massive matter. In both cases, extra Higgs vacuum states may appear when the Lagrangian involves nontrivial Yukawa interactions between the matter superfields. In addition, in 3d theories, massive fermion loops affect the index via renormalization of the Chern-Simons level k.Comment: 25 pages, 2 figures. Final version published in Nucl. Phys.

Low--dimensional sisters of Seiberg-Witten effective theory

We consider the theories obtained by dimensional reduction to D=1,2,3 of 4D supersymmetric Yang--Mills theories and calculate there the effective low-energy lagrangia describing moduli space dynamics -- the low-dimensional analogs of the Seiberg--Witten effective lagrangian. The effective theories thus obtained are rather beautiful and interesting from mathematical viewpoint. In addition, their study allows one to understand better some essential features of 4D supersymmetric theories, in particular -- the nonrenormalisation theorems.Comment: 39 pages. A contribution to Ian Kogan memorial volume. Minor corrections, a reference adde

Vacuum structure in supersymmetric Yang-Mills theories with any gauge group

We consider the pure supersymmetric Yang--Mills theories placed on a small 3-dimensional spatial torus with higher orthogonal and exceptional gauge groups. The problem of constructing the quantum vacuum states is reduced to a pure mathematical problem of classifying the flat connections on 3-torus. The latter problem is equivalent to the problem of classification of commuting triples of elements in a connected simply connected compact Lie group which is solved in this paper. In particular, we show that for higher orthogonal SO(N), N > 6, and for all exceptional groups the moduli space of flat connections involves several distinct connected components. The total number of vacuumstates is given in all cases by the dual Coxeter number of the group which agrees with the result obtained earlier with the instanton technique.Comment: 41 pages, 9 figures, 9 tables. Final version to be published in the Yuri Golfand memorial volume. We added the Appendix D with classification of all non-trivial commuting n-tuples for arbitrary