We study the decays of the τ -sleptons (τ 1,2 ) and τ -sneutrino (ν τ ) in the Minimal Supersymmetric Standard Model (MSSM) with complex parameters A τ , µ and M 1 (U(1) gaugino mass). We show that the effect of the CP phases of these parameters on the branching ratios ofτ 1,2 andν τ decays can be quite strong in a large region of the MSSM parameter space. This could have an important impact on the search forτ 1,2 andν τ and the determination of the MSSM parameters at future colliders.So far most phenomenological studies on supersymmetric (SUSY) particle searches have been performed in the Minimal Supersymmetric Standard Model (MSSM) [1] with real SUSY parameters. Studies of the 3rd generation sfermions are particularly interesting because of the effects of the large Yukawa couplings. The lighter sfermion mass eigenstates may be relatively light and they could be thoroughly studied at an e − e + linear collider [2]. They could also be copiously produced in the decays of heavier SUSY particles. An analysis of the decays of the 3rd generation sleptonsτ 2 andν τ in the MSSM with real parameters was performed in Ref. [3], and phenomenological studies of production and decays of the 3rd generation sfermions at future e − e + colliders in Ref. [4]. The assumption that all SUSY parameters are real, however, may be too restrictive. The higgsino mass parameter µ and the trilinear scalar coupling parameters A f of the sfermionsf may be complex. In minimal Supergravity-type models the phase of µ (ϕ µ ) turns out to be restricted by the experimental data on electron and neutron electric dipole moments (EDMs) to a range |ϕ µ | < ∼ 0.1 − 0.2 for a universal scalar mass parameter M 0 < ∼ 400GeV, while the phase of the universal trilinear scalar coupling parameter A 0 is correlated with ϕ µ , but otherwise unrestricted [5]. In more general models the phases of the parameters A f of the 3rd generation sfermions are not restricted at one-loop level by the EDM data. However, there may be restrictions at two-loop level [6]. In a complete phenomenological analysis of production and decays of the SUSY particles one has to take into account that the µ and A f may be complex. Furthermore, explicit CP violation in the Higgs sector can be induced by loop effects involving CP-violating interactions of Higgs bosons to top and bottom squark (t andb) sector with complex parameters [7,8]. It is found [9] that such effects of the complex phases on the phenomenology of the Higgs boson search could be quite significant. In principle, the imaginary parts of the possible complex SUSY parameters involved could most directly and unambiguously be determined by measuring relevant CP-violating observables; e.g. such analyses in τ -slepton (τ ) pair production in e + e − and µ + µ − colliders were performed in Ref. [10]. On the other hand, the CP-conserving observables also can depend on the phases of the complex parameters because in general the mass-eigenvalues and the couplings of the SUSY particles (sparticles) involved are functions of the ...

Early energy-momentum investigations for gravitating systems gave reference frame dependent pseudotensors; later the quasilocal idea was developed. Quasilocal energy-momentum can be determined by the Hamiltonian boundary term, which also identifies the variables to be held fixed on the boundary. We show that a pseudotensor corresponds to a Hamiltonian boundary term. Hence they are quasilocal and acceptable; each is the energy-momentum density for a definite physical situation with certain boundary conditions. These conditions are identified for well-known pseudotensors. *

No abstract

We present a systematic study of accelerating cosmologies obtained from M/string theory compactifications of hyperbolic spaces with time-varying volume. A set of vacuum solutions where the internal space is a product of hyperbolic manifolds is found to give qualitatively the same accelerating four-dimensional FLRW universe behavior as a single hyperbolic space. We also examine the possibility that our universe is a hyperbolic space and provide exact Milne type solutions, as well as intersecting S-brane solutions. When both the usual 4D spacetime and the m-dimensional internal space are hyperbolic, we find eternally accelerating cosmologies for m ≥ 7, with and without form field backgrounds. In particular, the effective potential for a magnetic field background in the large 3 dimensions is positive definite with a local minimum and thus enhances the eternally accelerating expansion.

The Hamiltonian for a gravitating region includes a boundary term which determines not only the quasi-local values but also, via the boundary variation principle, the boundary conditions. Using our covariant Hamiltonian formalism, we found four particular quasi-local energy-momentum boundary term expressions; each corresponds to a physically distinct and geometrically clear boundary condition. Here, from a consideration of the asymptotics, we show how a fundamental Hamiltonian identity naturally leads to the associated quasi-local energy flux expressions. For electromagnetism one of the four is distinguished: the only one which is gauge invariant; it gives the familiar energy density and Poynting flux. For Einstein's general relativity two different boundary condition choices correspond to quasi-local expressions which asymptotically give the ADM energy, the TrautmanBondi energy and, moreover, an associated energy flux (both outgoing and incoming). Again there is a distinguished expression: the one which is covariant.