Majorana Neutrino Masses Can Save One Family Technicolour

We make non perturbative estimates of the electroweak radiative correction parameter $S$ in dynamical symmetry breaking models with Majorana neutrino masses. The Majorana masses are treated as perturbations to a Non Local Chiral Model of the strong interactions. We argue that parameter ranges exist that would allow realistic values of $S$ and $T$ in one family Technicolour models.Comment: 15 pages plus appended diagrams (ps), Latex, SHEP 92/93--2

Oscillator model for the relativistic fermion-boson system

The solvable quantum mechanical model for the relativistic two-body system composed of spin-1/2 and spin-0 particles is constructed. The model includes the oscillator-type interaction through a combination of Lorentz-vector and -tensor potentials. The analytical expressions for the wave functions and the order of the energy levels are discussed.Comment: published version, 8 pages, 2 figure

Land resource assessment of Northern Belize (NRI Bulletin 43, Volume 1 of 2)

The land resource assessment was undertaken from July 1989 to June 1990 by the Natural Resources Institute (NRI) of the Overseas Development Administration (ODA), assisted by Mr. A. C. S. Wright, and Dr. M. Holder of Central Farm. The main object of the survey was to produce an updated land suitability assessment of Orange Walk, Corozal, Belize and Cayo districts which had not already been surveyed by Jenkin et al. (1976) and King et al. (1989). In addition, this survey would provide a land suitability assessment for the Belize Valley based on the soil mapping of )en kin et al. Thus, together with the land resource assessments of Toledo and Stann Creek districts (King et al., 1986, 1989 respectively), a land suitability assessment for the whole of Belize is now available

Land resource assessment of Northern Belize (NRI Bulletin 43, Volume 2 of 2)

The land resource assessment was undertaken from July 1989 to June 1990 by the Natural Resources Institute (NRI) of the Overseas Development Administration (ODA), assisted by Mr. A. C. S. Wright, and Dr. M. Holder of Central Farm. The main object of the survey was to produce an updated land suitability assessment of Orange Walk, Corozal, Belize and Cayo districts which had not already been surveyed by Jenkin et al. (1976) and King et al. (1989). In addition, this survey would provide a land suitability assessment for the Belize Valley based on the soil mapping of )en kin et al. Thus, together with the land resource assessments of Toledo and Stann Creek districts (King et al., 1986, 1989 respectively), a land suitability assessment for the whole of Belize is now available

Reconstructing the two right-handed neutrino model

In this paper we propose a low-energy parametrization of the two right-handed neutrino model, and discuss the prospects to determine experimentally these parameters in supersymmetric scenarios. In addition, we present exact formulas to reconstruct the high-energy leptonic superpotential in terms of the low-energy observables. We also discuss limits of the three right-handed neutrino model where this procedure applies.Comment: 28 pages, 4 figures. Typos corrected, references adde

Checking Properties Described by State Machines: On Synergy of Instrumentation, Slicing, and Symbolic Execution

We introduce a novel technique for checking properties described by finite state machines. The technique is based on a synergy of three well-known methods: instrumentation, program slicing, and symbolic execution. More precisely, we instrument a given program with a code that tracks runs of state machines representing various properties. Next we slice the program to reduce its size without affecting runs of state machines. And then we symbolically execute the sliced program to find real violations of the checked properties, i.e. real bugs. Depending on the kind of symbolic execution, the technique can be applied as a stand-alone bug finding technique, or to weed out some false positives from an output of another bug-finding tool. We provide several examples demonstrating the practical applicability of our technique.Představujeme novou techniku pro ověřování vlastností popsaných konečně-stavovými stroji. Tato technika je založena na synergii tří známých metod: instrumentace, prořezání programu a symbolické vykonání. Přesněji, instrumentujeme daný program kódem, který sleduje běh stavových strojů představujících různé vlastnosti. Dále program prořežeme, abychom zmenšili jeho velikost při zachování běhů stavových strojů. Nakonec prořezaný program symbolicky vykonáme, abychom našli skutečné porušení ověřovaných vlastností, t.j. skutečné chyby. Podle použitého druhu symbolického vykonání může být tato technika použita jako samostatná metoda pro detekci chyb nebo k vytřídění některých falešných hlášení z výstupu jiných nástrojů pro detekci chyb. Poskytujeme několik příkladů, které dokumentují praktickou použitelnost naší techniky

Search for varying constants of nature from astronomical observation of molecules

The status of searches for possible variation in the constants of nature from astronomical observation of molecules is reviewed, focusing on the dimensionless constant representing the proton-electron mass ratio $\mu=m_p/m_e$. The optical detection of H$_2$ and CO molecules with large ground-based telescopes (as the ESO-VLT and the Keck telescopes), as well as the detection of H$_2$ with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope is discussed in the context of varying constants, and in connection to different theoretical scenarios. Radio astronomy provides an alternative search strategy bearing the advantage that molecules as NH$_3$ (ammonia) and CH$_3$OH (methanol) can be used, which are much more sensitive to a varying $\mu$ than diatomic molecules. Current constraints are $|\Delta\mu/\mu| < 5 \times 10^{-6}$ for redshift $z=2.0-4.2$, corresponding to look-back times of 10-12.5 Gyrs, and $|\Delta\mu/\mu| < 1.5 \times 10^{-7}$ for $z=0.88$, corresponding to half the age of the Universe (both at 3$\sigma$ statistical significance). Existing bottlenecks and prospects for future improvement with novel instrumentation are discussed.Comment: Contribution to Workshop "High Performance Clocks in Space" at the International Space Science Institute, Bern 201

Maximally-localized Wannier functions for entangled energy bands

We present a method for obtaining well-localized Wannier-like functions (WFs) for energy bands that are attached to or mixed with other bands. The present scheme removes the limitation of the usual maximally-localized WFs method (N. Marzari and D. Vanderbilt, Phys. Rev. B 56, 12847 (1997)) that the bands of interest should form an isolated group, separated by gaps from higher and lower bands everywhere in the Brillouin zone. An energy window encompassing N bands of interest is specified by the user, and the algorithm then proceeds to disentangle these from the remaining bands inside the window by filtering out an optimally connected N-dimensional subspace. This is achieved by minimizing a functional that measures the subspace dispersion across the Brillouin zone. The maximally-localized WFs for the optimal subspace are then obtained via the algorithm of Marzari and Vanderbilt. The method, which functions as a postprocessing step using the output of conventional electronic-structure codes, is applied to the s and d bands of copper, and to the valence and low-lying conduction bands of silicon. For the low-lying nearly-free-electron bands of copper we find WFs which are centered at the tetrahedral interstitial sites, suggesting an alternative tight-binding parametrization.Comment: 13 pages, with 9 postscript figures embedded. Uses REVTEX and epsf macro

Neutral Higgs sector of the next-to-minimal supersymmetric standard model with explicit CP violation

The neutral Higgs sector of the next-to-minimal supersymmetric standard model (NMSSM) with explicit CP violation is investigated at the 1-loop level, using the effective potential method; not only the loops involving the third generation of quarks and scalar quarks, but also the loops involving $W$ boson, charged Higgs boson, and chargino are taken into account. It is found that for some parameter values of the NMSSM the contributions from the $W$ boson, charged Higgs boson, and chargino loops may modify the masses of the neutral Higgs bosons and the mixings among them significantly, depending on the CP phase. In $e^+e^-$ collisions, the prospects for discovering neutral Higgs bosons are investigated within the context of the NMSSM with explicit CP violation when the dominant component of the lightest neutral Higgs boson is the Higgs singlet field of the NMSSM.Comment: Latex, 23 pages, 6 figure

Non-linear regression models for Approximate Bayesian Computation

Approximate Bayesian inference on the basis of summary statistics is well-suited to complex problems for which the likelihood is either mathematically or computationally intractable. However the methods that use rejection suffer from the curse of dimensionality when the number of summary statistics is increased. Here we propose a machine-learning approach to the estimation of the posterior density by introducing two innovations. The new method fits a nonlinear conditional heteroscedastic regression of the parameter on the summary statistics, and then adaptively improves estimation using importance sampling. The new algorithm is compared to the state-of-the-art approximate Bayesian methods, and achieves considerable reduction of the computational burden in two examples of inference in statistical genetics and in a queueing model.Comment: 4 figures; version 3 minor changes; to appear in Statistics and Computin