W and Z Boson Production at sqrt(S)=1.96TeV with the D0 Detector

Preliminary measurements of the cross-section for the processes ppbar --> W --> mu nu, e nu; ppbar --> Z --> mu mu, e e, tau tau from the D0 detector are presented. Integrated luminosities for these data samples are 96 pb-1 for W --> mu nu, 177.3 pb-1 for W --> e nu and Z --> e e, 148pb-1 for Z --> mu mu and 207 pb-1 for Z --> tau tau. A measurement of the muon charge asymmetry from W boson decays (integrated luminosity 230 pb-1) and Z/gamma* --> e e inclusive differential cross section as a function of boson rapidity (integrated luminosity 337 pb-1) are presented as well. The results are in generally good agreement with SM predictions.Comment: Proceedings of a poster session at Hadron Collider Physics Symposium 2006 (HCP 2006), Duke University, Durham, NC, May 22-26 2006; 3 pages, 3 figure

Almost invariant half-spaces of algebras of operators

Given a Banach space X and a bounded linear operator T on X, a subspace Y of X is almost invariant under T if TY is a subspace of Y+F for some finite-dimensional ``error'' F. In this paper, we study subspaces that are almost invariant under every operator in an algebra A of operators acting on X. We show that if A is norm closed then the dimensions of ``errors'' corresponding to operators in A must be uniformly bounded. Also, if A is generated by a finite number of commuting operators and has an almost invariant half-space (that is, a subspace with both infinite dimension and infinite codimension) then A has an invariant half-space.Comment: 14 page

Extremal black disks in QCD

We argue that in the high energy QCD a true black disk wave function necessarily contains many quarks. This corresponds to necessity of non-vacuum reggeon loops in formation of a black disk. The result comes from decomposition of the black disk S-matrix in characters on group manifold.Comment: 5 pages, significantly improved tex

On matrix semigroups bounded above and below

An irreducible norm closed semigroup of complex matrices is simultaneously similar to a semigroup of partial isometries if and only if (a) the norms of all nonzero members of it are uniformly bounded above and below, and (b) its idempotents commute. This is a generalization of the well-known result on bounded groups

Every operator has almost-invariant subspaces

We show that any bounded operator $T$ on a separable, reflexive, infinite-dimensional Banach space $X$ admits a rank one perturbation which has an invariant subspace of infinite dimension and codimension. In the non-reflexive spaces, we show that the same is true for operators which have non-eigenvalues in the boundary of their spectrum. In the Hilbert space, our methods produce perturbations that are also small in norm, improving on an old result of Brown and Pearcy.Comment: 11 page

Semigroups of Partial Isometries

We study self-adjoint semigroups of partial isometries on a Hilbert space. These semigroups coincide precisely with faithful representations of abstract inverse semigroups. Groups of unitary operators are specialized examples of self-adjoint semigroups of partial isometries. We obtain a general structure result showing that every self-adjoint semigroup of partial isometries consists of "generalized weighted composition" operators on a space of square-integrable Hilbert-space valued functions. If the semigroup is irreducible and contains a compact operator then the underlying measure space is purely atomic, so that the semigroup is represented as "zero-unitary" matrices. In this case it is not even required that the semigroup be self-adjoint.Comment: To appear in Semigroup Foru

An operational definition of the 100 second blocking temperature TB100_{\mathrm{B}100} for single molecule magnets

An important figure of merit for the performance of single-molecule magnets (SMMs) is the 100 s blocking temperature T$_{\mathrm{B}100}$. It is the temperature at which the remanence or zero field relaxation time is 100 seconds. If there is more than one relaxation process of the magnetisation, the determination of the relaxation times may, however, become ambiguous. Here we propose an operational definition for the zero-field magnetic relaxation times from which T$_{\mathrm{B}100}$ may be determined. This definition allows for a direct comparison of the performance of different samples independent of the details of the relaxation processes involved in the demagnetization.Comment: 4 pages, 2 figure

Traversable wormholes in four dimensions

We present a wormhole solution in four dimensions. It is a solution of an Einstein Maxwell theory plus charged massless fermions. The fermions give rise to a negative Casimir-like energy, which makes the wormhole possible. It is a long wormhole that does not lead to causality violations in the ambient space. It can be viewed as a pair of entangled near extremal black holes with an interaction term generated by the exchange of fermion fields. The solution can be embedded in the Standard Model by making its overall size small compared to the electroweak scale.Comment: 28+10 pages, 8 figures. v2: Further restriction on the regime of validity in section 5.5. References adde

Preliminary results of giant pulse investigations from Crab pulsar with Radioastron

Giant pulses from Crab pulsar were observed together with Radioastron space radiotelescope, Global EVN radio telescopes and Kvazar-KVO VLBI stations to study the scattering effects in the ISM. Five observing sessions were conducted at 18 cm (EVN codes: EG060A, EG060B, EG067B, EG075) and one at 92 cm (EVN code: GS033A). We have estimated distance to the scattering screen, angular size of scattering disk, scattering time. All estimations were done in an assumption of single thin scattering screen. Also, a significant change in the shape of cross-correlation functions for space-ground baselines was found (starting from 4 up to 12 Earth diameters)

The role of AGK theorem in QCD

We rise the question about a role of AGK theorem in QCD. Considering multiple-gluons emissions in a scattering process, we formulate the AGK-like rules of calculation of exclusive gluon distributions. The result shows that the naive extrapolation of the soft AGK, based on the pomeron idea, is not constructive and one should find a more generalized formulation.Comment: 13 page