Minimal model theory for log surfaces

We discuss the log minimal model theory for log surfaces. We show that the log minimal model program, the finite generation of log canonical rings, and the log abundance theorem for log surfaces hold true under assumptions weaker than the usual framework of the log minimal model theory.Comment: 34 pages, v2: Section 8 is new, v3: minor revisio

Dynamic sharing of a multiple access channel

In this paper we consider the mutual exclusion problem on a multiple access channel. Mutual exclusion is one of the fundamental problems in distributed computing. In the classic version of this problem, n processes perform a concurrent program which occasionally triggers some of them to use shared resources, such as memory, communication channel, device, etc. The goal is to design a distributed algorithm to control entries and exits to/from the shared resource in such a way that in any time there is at most one process accessing it. We consider both the classic and a slightly weaker version of mutual exclusion, called ep-mutual-exclusion, where for each period of a process staying in the critical section the probability that there is some other process in the critical section is at most ep. We show that there are channel settings, where the classic mutual exclusion is not feasible even for randomized algorithms, while ep-mutual-exclusion is. In more relaxed channel settings, we prove an exponential gap between the makespan complexity of the classic mutual exclusion problem and its weaker ep-exclusion version. We also show how to guarantee fairness of mutual exclusion algorithms, i.e., that each process that wants to enter the critical section will eventually succeed

Constraints on the Wtb vertex from early LHC data

We use the recent measurements of top quark decay asymmetries in ATLAS and the t-channel single top cross section in CMS to set the first combined LHC limits on the Wtb vertex. This combination allows to obtain much better limits than the separate measurements. The resulting constraints are comparable, although still weaker, than the ones obtained using Tevatron data with much more statistics.Comment: RevTeX 4 page

Demand Dispersion, Metonymy and Ideal Panel Data

In a generic competitive economy with constant returns production and "increasing dispersion," market demand satisfies the weak axiom of revealed preference and equilibrium is unique. Increasing dispersion requires, roughly, that when the households' incomes rise slightly their demand vectors move apart. We show how to test for it using panel data with fixed relative prices under a "structural stability" hypothesis due to Hildenbrand and Kneip (1999). We also show how to test for it using cross section data if the households' demand functions and incomes are independently distributed, or under a much weaker condition called "dispersion metonymy." We show that this weaker condition is untestable---even with ideal panel data that allow a direct test of increasing dispersion. Thus, cross section tests of increasing dispersion rely on an assumption that is not potentially falsifiable.Aggregation, Weak Axiom, Increasing Dispersion, Cross Section, Structural Stability

Vector Leptoquark Pair Production in e+e−e^+e^- Annihilation

The cross section for vector leptoquark pair production in $e^+e^-$ annihilation is calculated for the case of finite anomalous gauge boson couplings $\kappa_{\gamma, Z}$ and $\lambda_{\gamma, Z}$. The minimal cross section is found to behave $\propto \beta^7$, leading to weaker mass bounds in the threshold range than in models studied previously.Comment: 10 pages Latex, including 5 eps-figure

New CP Violation in Neutrino Oscillations

Measurements of CP--violating observables in neutrino oscillation experiments have been studied in the literature as a way to determine the CP--violating phase in the mixing matrix for leptons. Here we show that such observables also probe new neutrino interactions in the production or detection processes. Genuine CP violation and fake CP violation due to matter effects are sensitive to the imaginary and real parts of new couplings. The dependence of the CP asymmetry on source--detector distance is different from the standard one and, in particular, enhanced at short distances. We estimate that future neutrino factories will be able to probe in this way new interactions that are up to four orders of magnitude weaker than the weak interactions. We discuss the possible implications for models of new physics.Comment: ReVTeX, 28 pages, 7 figues. v2: Modifications in section VIII to reflect the fact that some of the couplings that were discussed in this section are irrelevant to our analysis (as pointed out in hep-ph/0112329); Added a discussion in section IX of the relevance of other future experiments that will search for lepton flavor violatio