String Indexing for Patterns with Wildcards

We consider the problem of indexing a string $t$ of length $n$ to report the occurrences of a query pattern $p$ containing $m$ characters and $j$ wildcards. Let $occ$ be the number of occurrences of $p$ in $t$, and $\sigma$ the size of the alphabet. We obtain the following results. - A linear space index with query time $O(m+\sigma^j \log \log n + occ)$. This significantly improves the previously best known linear space index by Lam et al. [ISAAC 2007], which requires query time $\Theta(jn)$ in the worst case. - An index with query time $O(m+j+occ)$ using space $O(\sigma^{k^2} n \log^k \log n)$, where $k$ is the maximum number of wildcards allowed in the pattern. This is the first non-trivial bound with this query time. - A time-space trade-off, generalizing the index by Cole et al. [STOC 2004]. We also show that these indexes can be generalized to allow variable length gaps in the pattern. Our results are obtained using a novel combination of well-known and new techniques, which could be of independent interest

Post-AGB stars with hot circumstellar dust: binarity of the low-amplitude pulsators

While the first binary post-AGB stars were serendipitously discovered, the distinct characteristics of their Spectral Energy Distribution (SED) allowed us to launch a more systematic search for binaries. We selected post-AGB objects which show a broad dust excess often starting already at H or K, pointing to the presence of a gravitationally bound dusty disc in the system. We started a very extensive multi-wavelength study of those systems and here we report on our radial velocity and photometric monitoring results for six stars of early F type, which are pulsators of small amplitude. To determine the radial velocity of low signal-to-noise time-series, we constructed dedicated auto-correlation masks. The radial velocity variations were subjected to detailed analysis to differentiate between pulsational variability and variability due to orbital motion. Finally orbital minimalisation was performed to constrain the orbital elements. All of the six objects are binaries, with orbital periods ranging from 120 to 1800 days. Five systems have non-circular orbits. The mass functions range from 0.004 to 0.57 solar mass and the companions are likely unevolved objects of (very) low initial mass. We argue that these binaries must have been subject to severe binary interaction when the primary was a cool supergiant. Although the origin of the circumstellar disc is not well understood, the disc is generally believed to be formed during this strong interaction phase. The eccentric orbits of these highly evolved objects remain poorly understood. With the measured orbits and mass functions we conclude that the circumbinary discs seem to have a major impact on the evolution of a significant fraction of binary systems.Comment: 13 pages, 15 figures, accepted for Astronomy and Astrophysic

Gluons at finite temperature in Landau gauge Yang--Mills theory

The infrared behavior of Yang-Mills theory at finite temperature provides access to the role of confinement. In this review recent results on this topic from lattice calculations and especially Dyson-Schwinger studies are discussed. These indicate persistence of a residual confinement even in the high-temperature phase. The confinement mechanism is very similar to the one in the vacuum for the chromomagnetic sector. In the chromoelectric sector screening occurs at the soft scale g^2T, although not leading to a perturbative behavior.Comment: 15 pages, 4 figures, invited brief review for MPL

The Chemical Compositions of the Type II Cepheids -- The BL Her and W Vir Variables

Abundance analyses from high-resolution optical spectra are presented for 19 Type II Cepheids in the Galactic field. The sample includes both short-period (BL Her) and long-period (W Vir) stars. This is the first extensive abundance analysis of these variables. The C, N, and O abundances with similar spreads for the BL Her and W Vir show evidence for an atmosphere contaminated with $3\alpha$-process and CN-cycling products. A notable anomaly of the BL Her stars is an overabundance of Na by a factor of about five relative to their presumed initial abundances. This overabundance is not seen in the W Vir stars. The abundance anomalies running from mild to extreme in W Vir stars but not seen in the BL Her stars are attributed to dust-gas separation that provides an atmosphere deficient in elements of high condensation temperature, notably Al, Ca, Sc, Ti, and $s$-process elements. Such anomalies have previously been seen among RV Tau stars which represent a long-period extension of the variability enjoyed by the Type II Cepheids. Comments are offered on how the contrasting abundance anomalies of BL Her and W Vir stars may be explained in terms of the stars' evolution from the blue horizontal branch.Comment: 41 pages including 11 figures and 4 tables; Accepted for publication in Ap

On the gauge boson's properties in a candidate technicolor theory

The technicolor scenario replaces the Higgs sector of the standard model with a strongly interacting sector. One candidate for a realization of such a sector is two-technicolor Yang-Mills theory coupled to two degenerate flavors of adjoint, massless techniquarks. Using lattice gauge theory the properties of the technigluons in this scenario are investigated as a function of the techniquark mass towards the massless limit. For that purpose the minimal Landau gauge two-point and three-point correlation functions are determined, including a detailed systematic error analysis. The results are, within the relatively large systematic uncertainties, compatible with a behavior very similar to QCD at finite techniquark mass. However, the limit of massless techniquarks exhibits features which could be compatible with a (quasi-)conformal behavior.Comment: 27 pages, 17 figures, 1 table; v2: persistent notational error corrected, some minor modification

The HypHI project: Hypernuclear spectroscopy with stable heavy ion beams and rare isotope beams at GSI and FAIR

The HypHI collaboration aims to perform a precise hypernuclear spectroscopy with stable heavy ion beams and rare isotope beams at GSI and fAIR in order to study hypernuclei at extreme isospin, especially neutron rich hypernuclei to look insight hyperon-nucleon interactions in the neutron rich medium, and hypernuclear magnetic moments to investigate baryon properties in the nuclei. We are currently preparing for the first experiment with $^6$Li and $^{12}$C beams at 2 AGeV to demonstrate the feasibility of a precise hypernuclear spectroscopy by identifying $^{3}_{\Lambda}$H, $^{4}_{\Lambda}$H and $^{5}_{\Lambda}$He. The first physics experiment on these hypernuclei is planned for 2009. In the present document, an overview of the HypHI project and the details of this first experiment will be discussed.Comment: 5 pages, 2 figures, French-Japanese symposium 2008, Paris (France

Accessing directly the properties of fundamental scalars in the confinement and Higgs phase

The properties of elementary particles are encoded in their respective propagators and interaction vertices. For a SU(2) gauge theory coupled to a doublet of fundamental complex scalars these propagators are determined in both the Higgs phase and the confinement phase and compared to the Yang-Mills case, using lattice gauge theory. Since the propagators are gauge-dependent, this is done in the Landau limit of 't Hooft gauge, permitting to also determine the ghost propagator. It is found that neither the gauge boson nor the scalar differ qualitatively in the different cases. In particular, the gauge boson acquires a screening mass, and the scalar's screening mass is larger than the renormalized mass. Only the ghost propagator shows a significant change. Furthermore, indications are found that the consequences of the residual non-perturbative gauge freedom due to Gribov copies could be different in the confinement and the Higgs phase.Comment: 11 pages, 6 figures, 1 table; v2: one minor error corrected; v3: one appendix on systematic uncertainties added and some minor changes, version to appear in EPJ

Measurement of Strange Quark Contributions to the Nucleon's Form Factors at Q^2=0.230 (GeV/c)^2

We report on a measurement of the parity-violating asymmetry in the scattering of longitudinally polarized electrons on unpolarized protons at a $Q^2$ of 0.230 (GeV/c)^2 and a scattering angle of \theta_e = 30^o - 40^o. Using a large acceptance fast PbF_2 calorimeter with a solid angle of \Delta\Omega = 0.62 sr the A4 experiment is the first parity violation experiment to count individual scattering events. The measured asymmetry is A_{phys} =(-5.44 +- 0.54_{stat} +- 0.27_{\rm sys}) 10^{-6}. The Standard Model expectation assuming no strangeness contributions to the vector form factors is $A_0=(-6.30 +- 0.43) 10^{-6}$. The difference is a direct measurement of the strangeness contribution to the vector form factors of the proton. The extracted value is G^s_E + 0.225 G^s_M = 0.039 +- 0.034 or F^s_1 + 0.130 F^s_2 = 0.032 +- 0.028.Comment: 5 pages, 3 figures, submitted to Phys. Rev. Letters on Dec 11, 200

Resolving the compact dusty discs around binary post-AGB stars using N-band interferometry

We present the first mid-IR long baseline interferometric observations of the circumstellar matter around binary post-AGB stars. Two objects, SX Cen and HD 52961, were observed using the VLTI/MIDI instrument during Science Demonstration Time. Both objects are known binaries for which a stable circumbinary disc is proposed to explain the SED characteristics. This is corroborated by our N-band spectrum showing a crystallinity fraction of more than 50 % for both objects, pointing to a stable environment where dust processing can occur. Surprisingly, the dust surrounding SX Cen is not resolved in the interferometric observations providing an upper limit of 11 mas (or 18 AU at the distance of this object) on the diameter of the dust emission. This confirms the very compact nature of its circumstellar environment. The dust emission around HD 52961 originates from a very small but resolved region, estimated to be ~ 35 mas at 8 micron and ~ 55 mas at 13 micron. These results confirm the disc interpretation of the SED of both stars. In HD 52961, the dust is not homogeneous in its chemical composition: the crystallinity is clearly concentrated in the hotter inner region. Whether this is a result of the formation process of the disc, or due to annealing during the long storage time in the disc is not clear.Comment: 12 pages, 10 figures, accepted for publication in A &