Working group report: Collider Physics

This is summary of the activities of the working group on collider physics in the IXth Workshop on High Energy Physics Phenomenology (WHEPP-9) held at the Institute of Physics, Bhubaneswar, India in January 2006. Some of the work subsequently done on these problems by the subgroups formed during the workshop is included in this report.     

Classical, phenomenological analysis of the kinetics of reactions at the gas-exposed surface of mixed ionic electronic conductors

The kinetics of reactions occurring at the gas-exposed surfaces of charged mixed ionic electronic conductors (MIECs) are examined from theoretical first principles. Analysis based on the classical electrochemical potential-transition state theory model reveals that the nature of the reactions is electrochemical in general. However, the influence of the surface potential on the reaction rate is opposite for adsorption and incorporation reactions. Two-dimensional finite volume models of an MIEC as working electrode in a half-cell configuration are presented. The results for a simple, two-step reduction process show that the effect of the surface potential on the rate of reactions is minimal for incorporation-limited reactions but more influential for adsorption-limited reactions. An erratum to this article is available at .     

Nonvanishing cohomology and classes of Gorenstein rings

We give counterexamples to the following conjecture of Auslander: given a finitely generated module M over an Artin algebra Λ, there exists a positive integer n_M such that for all finitely generated Λ-modules N, if Ext_Λⁱ(M,N)=0 for all i?0, then Ext_Λⁱ(M,N)=0 for all i?n_M. Some of our examples moreover yield homologically defined classes of commutative local rings strictly between the class of local complete intersections and the class of local Gorenstein rings.     

Magnetic hysteresis of the magnetoresistance and the critical current density in polycrystalline YBa2Cu3O7−δ–Ag superconductors

A systematic study of the magnetic hysteresis in transport properties of polycrystalline YBa₂Cu₃O_7−δ–Ag compounds has been made based on two kinds of measurements at 77 K and under applied magnetic fields up to 30 mT: critical current density J_c(B_a) and magnetoresistance R(B_a). The R(B_a) curves show a minimum in their decreasing branch occurring at B=B_min which was found to be both the excitation current I_ex and the maximum applied magnetic field B_am dependent. In addition, for a certain value of B_am>5 mT, we have observed that B_min increases with increasing I_ex and reaches a saturation value. The J_c(B_a) curves show a maximum in decreasing applied magnetic fields occurring at B=B_max. We have also found that B_max increases with increasing B_am and reaches a saturation value. The minimum in the R(B_a) and the maximum in J_c(B_a) curves were found to be related to the trapped flux within the grains. All the experimental results are discussed within the context of the flux dynamics and transport mechanisms in these high-T_c materials.     

Broadening the scope of 1,2,4-triazine synthesis by the application of microwave technology

By the application of microwave technology, a general protocol has been developed for the rapid synthesis of diverse 3,5,6-trisubstituted 1,2,4-triazines in excellent yield and purity, including many previously unknown 3-heterocyclic-1,2,4-triazines.     

Vojta's Main Conjecture for blowup surfaces

In this paper, we prove Vojta's Main Conjecture for split blowups of products of certain elliptic curves with themselves. We then deduce from the conjecture bounds on the average number of rational points lying on curves on these surfaces, and expound upon this connection for abelian surfaces and rational surfaces.

     

Parametric multiple sequence alignment and phylogeny construction

Bounds are given on the size of the parameter-space decomposition induced by multiple sequence alignment problems where phylogenetic information may be given or inferred. It is shown that many of the usual formulations of these problems fall within the same integer parametric framework, implying that the number of distinct optima obtained as the parameters are varied across their ranges is polynomially bounded in the length and number of sequences.     

Stark's conjecture over complex cubic number fields

Systematic computation of Stark units over nontotally real base fields is carried out for the first time. Since the information provided by Stark's conjecture is significantly less in this situation than the information provided over totally real base fields, new techniques are required. Precomputing Stark units in relative quadratic extensions (where the conjecture is already known to hold) and coupling this information with the Fincke-Pohst algorithm applied to certain quadratic forms leads to a significant reduction in search time for finding Stark units in larger extensions (where the conjecture is still unproven). Stark's conjecture is verified in each case for these Stark units in larger extensions and explicit generating polynomials for abelian extensions over complex cubic base fields, including Hilbert class fields, are obtained from the minimal polynomials of these new Stark units.

     

An optical fibre pH sensor based on dye doped mesostructured silica

This paper describes the synthesis and optical pH sensing properties of a pH indicator dye activated mesostructured silica coated optical fibre. The pH-sensitive dye bromothymol blue was incorporated into the mesostructure sol precursor and thin films/coatings were used for pH-sensing applications without prior removal of the surfactant. The pH sensitivity range and operating wavelength were analysed by absorption measurements on layer dip-coated on glass slides. The pH sensing properties of coated optical fibre were tested by evanescent wave method. Experiments were carried out by using a series of solutions of known pH. No leaching was observed (except at very high pH) and an excellent reversibility was obtained between pH=2 and 5.     

An experimental investigation of Curle's theory of aerodynamic noise generation by a stationary body in a turbulent air stream

Bies et al. (J. Sound Vib. 204(4) (1997) 631) investigated Curle's theory (Proc. R. Soc. Ser. A 231 (1955) 505) published in 1955 over a wide range of flow speeds from about 50-200 m/s and found only partial agreement with the experimental data. Here the experimental investigation has been repeated allowing the data to be recorded in a format amenable to analysis, which was not previously possible.Reintroduction of a term neglected by Curle has been found necessary as Curle's compact source condition ensures so low a radiation impedance that the effect cannot be detected in the jet background noise. The reintroduction of the term, which has been neglected, allows his analysis to include radiation from sources not compact but less than half a wavelength in characteristic dimension. It is shown that the power ratio defined as the measured sound power divided by Curle's amended prediction converges to about 3 whereas Curle predicts that the power ratio should converge to 1 as the wave number converges to zero. The introduction of the empirically determined constant 3 into Curle's prediction brings the measurements into very good agreement with prediction over the entire range of the non-dimensional wave numbers from about 0.4 to 3.2.