A New Measurement of Exclusive \boldmathρ∘\rho^{\circ} Photoproduction at HERA

Exclusive $\rho^{\circ}$ photoproduction has been measured with high statistics by the H1 Collaboration. The kinematical range is $20 < W < 90$ GeV, $|t|<3$ GeV$^2$ and $Q^2<4$ GeV$^2$. Cross sections are measured differentially in $W$ and $t$ and allow the extraction of the Pomeron trajectory, for the first time using $\rho^{\circ}$ photoproduction data of one single experiment. The preliminary result, $\alpha_{\mathbb{P}} (t) = 1.093 \pm 0.003 (stat.) ^{+0.008}_{-0.007} (syst.) + (0.116 \pm 0.027 (stat.) ^{+0.036}_{-0.046} (syst.)$ GeV$^{-2} \cdot t$, deviates significantly from the canonical expectation.Comment: 4 pages, 2 figures (requires class ws-procs9x6); Talk presented in the 14th International Workshop on Deep Inelastic Scattering, April 2006, Tsukuba, Japan; To appear in the Proceeding

Justifying the State from Rights-Based Libertarian Premises

Although many libertarians share similar moral foundations, they disagree about whether the state can be justified. The most famous libertarian attempt to justify the state is that of Robert Nozick. This attempt has been criticized by, among others, the libertarian anarchist Murray Rothbard. In this article, Nozick’s theory and Rothbard’s critique are discussed, as well as some other attempts to justify the state from libertarian premises. Keeping the criticisms of those theories in mind, an alternative theory, which attempts to bypass the criticisms, is put forward. This alternative theory explains how a state—most probably a nonminimal democratic state—can legitimately be formed in a condition of anarchy without violating anyone’s libertarian rights. One result of this is that the rights-based case for minarchism is severely weakened

A theorem on the cores of partitions

If s and t are relatively prime positive integers we show that the s-core of a t-core partition is again a t-core partitionComment: 9 page

The JT9D Jet Engine Diagnostics Program

The various engine deterioration phenomena that affect JT9D performance retention were studied, and approaches to improve performance retention of engines were identified. The program included surveys of historical data, monitoring of in service engines, ground and flight testing of instrumented engines, analysis, and analytical modeling. Performance deterioration is made up of both short and long term modes, both of which are flight cycle related phenomena. Short term deterioration occurs primarily during airplane acceptance testing prior to delivery to the airline. This effect is caused by flight load and power induced clearance closures and engine deflections with resulting rubbing of airfoils and seals. Long term deterioration is caused by erosion of airfoils and gas path seals during ground operation and take off and by cyclic induced thermal distortion of the high pressure turbine airfoils. Studies of possible remedial approaches have shown that performance retention within 1 to 2 percent of initial revenue service performance can be achieved with a proper program of hot section and cold section maintenance

Asymmetric velocity correlations in shearing media

A model of soft frictionless disks in two dimensions at zero temperature is simulated with a shearing dynamics to study various kinds of asymmetries in sheared systems. We examine both single particle properties, the spatial velocity correlation function, and a correlation function designed to separate clockwise and counter-clockwise rotational fields from one another. Among the rich and interesting behaviors we find that the velocity correlation along the two different diagonals corresponding to compression and dilation, respectively, are almost identical and, furthermore, that a feature in one of the correlation functions is directly related to irreversible plastic events