A Monopole-Antimonopole Solution of the SU(2) Yang-Mills-Higgs Model

As shown by Taubes, in the Bogomol'nyi-Prasad-Sommerfield limit the SU(2) Yang-Mills-Higgs model possesses smooth finite energy solutions, which do not satisfy the first order Bogomol'nyi equations. We construct numerically such a non-Bogomol'nyi solution, corresponding to a monopole-antimonopole pair, and extend the construction to finite Higgs potential.Comment: 11 pages, including 4 eps figures, LaTex format using RevTe

Multisphalerons in the Weinberg-Salam Theory

We construct multisphaleron solutions in the Weinberg-Salam theory. The multisphaleron solutions carry Chern-Simons charge $n/2$, where $n$ is an integer, counting the winding of the fields in the azimuthal angle. The well-known sphaleron has $n=1$. The multisphalerons possess axial symmetry and parity reflection symmetry. We vary the Higgs mass and the mixing angle. For small $n$ the energies of the multisphalerons are on the order of $n$ times the energy of the sphaleron and their magnetic dipole moments are on the order of $n$ times the magnetic dipole moment of the sphaleron.Comment: 18 pages, latex, 17 figures in uuencoded postscript files. THU-94/1

Static black hole solutions with axial symmetry

We construct a new class of asymptotically flat black hole solutions in Einstein-Yang-Mills and Einstein-Yang-Mills-dilaton theory. These black hole solutions are static, and they have a regular event horizon. However, they possess only axial symmetry. Like their regular counterparts, the black hole solutions are characterized by two integers, the winding number $n$ and the node number $k$ of the gauge field functions.Comment: 14 pages, including 4 postscript figures, LaTe

Rotating Hairy Black Holes

We construct stationary black holes in SU(2) Einstein-Yang-Mills theory, which carry angular momentum and electric charge. Possessing non-trivial non-abelian magnetic fields outside their regular event horizon, they represent non-perturbative rotating hairy black holes.Comment: 13 pages, including 4 eps figures, LaTex forma

Static Axially Symmetric Solutions of Einstein-Yang-Mills-Dilaton Theory

We construct static axially symmetric solutions of SU(2) Einstein-Yang-Mills-dilaton theory. Like their spherically symmetric counterparts, these solutions are nonsingular and asymptotically flat. The solutions are characterized by the winding number n and the node number k of the gauge field functions. For fixed n with increasing k the solutions tend to ``extremal'' Einstein-Maxwell-dilaton black holes with n units of magnetic charge.Comment: 11 pages, including 2 postscript figure

Static Axially Symmetric Einstein-Yang-Mills-Dilaton Solutions: II.Black Hole Solutions

We discuss the new class of static axially symmetric black hole solutions obtained recently in Einstein-Yang-Mills and Einstein-Yang-Mills-dilaton theory. These black hole solutions are asymptotically flat and they possess a regular event horizon. The event horizon is almost spherically symmetric with a slight elongation along the symmetry axis. The energy density of the matter fields is angle-dependent at the horizon. The static axially symmetric black hole solutions satisfy a simple relation between mass, dilaton charge, entropy and temperature. The black hole solutions are characterized by two integers, the winding number $n$ and the node number $k$ of the purely magnetic gauge field. With increasing node number the magnetically neutral black hole solutions form sequences tending to limiting solutions with magnetic charge $n$, corresponding to Einstein-Maxwell-dilaton black hole solutions for finite dilaton coupling constant and to Reissner-Nordstr\o m black hole solutions for vanishing dilaton coupling constant.Comment: 41 pages including 45 postscript figures, RevTex forma

A Slow-Cycling Proton Driver for a Neutrino Factory

An 8 Hz proton driver for a neutrino factory of 4 MW beam power and an energy of 25-30 GeV is under study at CERN, in parallel with a similar investigation using a 2.2 GeV high-energy linac and an accumulator plus a compressor ring cycling at 75 Hz. At RAL, synchrotron drivers with final energies of 5 and 15 GeV cycling at 50 and 25 Hz, respectively, are being studied. With these four scenarios, one hopes to cope with all possible constraints emerging from the studies of the pion production target and the muon rotation and cooling system. The high beam energy of this scenario requires less proton current and could inject into the SPS above transition and upgrade LHC and fixed target physics. Its 440 kW booster would upgrade ISOLDE.The main problems of the driver synchrotron are: the requirement of about 4 MV RF voltage at 10 MHz for acceleration and adiabatic bunch compression to the required r.m.s length of 1 ns; the sensitivity of the compression to the impedance of the vacuum chamber and to non-linearities of the momentum compaction of the high-gt lattice

Einstein-Gauss-Bonnet black strings

We construct uniform black-string solutions in Einstein-Gauss-Bonnet gravity for all dimensions $d$ between five and ten and discuss their basic properties. Closed form solutions are found by taking the Gauss-Bonnet term as a perturbation from pure Einstein gravity. Nonperturbative solutions are constructed by solving numerically the equations of the model. The Gregory-Laflamme instability of the black strings is explored via linearized perturbation theory. Our results indicate that new qualitative features occur for $d=6$, in which case stable configurations exist for large enough values of the Gauss-Bonnet coupling constant. For other dimensions, the black strings are dynamically unstable and have also a negative specific heat. We argue that this provides an explicit realization of the Gubser-Mitra conjecture, which links local dynamical and thermodynamic stability. Nonuniform black strings in Einstein-Gauss-Bonnet theory are also constructed in six spacetime dimensions.Comment: 33 pages, 11 figure

New generalized nonspherical black hole solutions

We present numerical evidence for the existence of several types of static black hole solutions with a nonspherical event horizon topology in $d\geq 6$ spacetime dimensions. These asymptotically flat configurations are found for a specific metric ansatz and can be viewed as higher dimensional counterparts of the $d=5$ static black rings, dirings and black Saturn. Similar to that case, they are supported against collapse by conical singularities. The issue of rotating generalizations of these solutions is also considered.Comment: 47 pages, 11 figures, some comments adde