Tunable Causal Consistency: Specification and Implementation

To achieve high availability and low latency, distributed data stores often geographically replicate data at multiple sites called replicas. However, this introduces the data consistency problem. Due to the fundamental tradeoffs among consistency, availability, and latency in the presence of network partition, no a one-size-fits-all consistency model exists. To meet the needs of different applications, many popular data stores provide tunable consistency, allowing clients to specify the consistency level per individual operation. In this paper, we propose tunable causal consistency (TCC). It allows clients to choose the desired session guarantee for each operation, from the well-known four session guarantees, i.e., read your writes, monotonic reads, monotonic writes, and writes follow reads. Specifically, we first propose a formal specification of TCC in an extended (vis,ar) framework originally proposed by Burckhardt et al. Then we design a TCC protocol and develop a prototype distributed key-value store called TCCSTORE. We evaluate TCCSTORE on Aliyun. The latency is less than 38ms for all workloads and the throughput is up to about 2800 operations per second. We also show that TCC achieves better performance than causal consistency and requires a negligible overhead when compared with eventual consistency

Statistical hadronization with resonances

We introduce the equilibrium and non-equilibrium statistical hadronization picture of particle production in ultra-relativistic heavy ion collisions. We describe the related physical reaction scenarios, and show how these can lead to quark pair yield non-equilibrium. Using the SHARE1.2 program suite we quantitatively model particle yields and ratios for RHIC-130 run. We study how experimental particle ratios can differentiate between model scenarios, and discuss in depth the importance of hadronic resonances in understanding of hadron production processes.Comment: Presented at the XLIV Crakow School of Theoretical Physic

U(1)_A Topological Susceptibility and its Slope, Pseudoscalar Gluonium and the Spin of the Proton

We review the determinations of the pseudoscalar glueball and eventual radial excitation of the \eta' masses and decay constants from QCD spectral sum rules (QSSR). The glueball mass is (2.05+-0.19) which one can compare with the eventual experimental candidate X(1835), while the \eta(1400) is likely a radial excitation of the \eta'-meson. Their effects on the estimates of U(1)_A topological susceptibility and its slope as well as the impact of the latter in the estimate of the spin of the proton is discussed. We predict the singlet polarized parton distributions to be a^0(Q^2=4 GeV^2)=0.32+-0.02, which is about a factor two smaller than the OZI value, but comparable with the COMPASS measurement of 0.24+-0.02.Comment: 12 pages latex file. In honour of Professor A. Di Giacomo for his 70th birthday (Adrianofest 26-27th January 2006, Pisa, Italy). To appear in the Proceeding

A robust upper limit on N_eff from BBN, circa 2011

We derive here a robust bound on the effective number of neutrinos from constraints on primordial nucleosynthesis yields of deuterium and helium. In particular, our results are based on very weak assumptions on the astrophysical determination of the helium abundance, namely that the minimum effect of stellar processing is to keep constant (rather than increase, as expected) the helium content of a low-metallicity gas. Using the results of a recent analysis of extragalactic HII regions as upper limit, we find that Delta Neff<= 1 at 95 % C.L., quite independently of measurements on the baryon density from cosmic microwave background anisotropy data and of the neutron lifetime input. In our approach, we also find that primordial nucleosynthesis alone has no significant preference for an effective number of neutrinos larger than the standard value. The ~2 sigma hint sometimes reported in the literature is thus driven by CMB data alone and/or is the result of a questionable regression protocol to infer a measurement of primordial helium abundance.Comment: 5 pages, 1 table, 1 figure. Minor improvements and extensions in the analysis, clarifications and reference added, conclusions slightly strengthened. Matches version published in Phys. Lett.

The Canis Major Dwarf Galaxy

Recent observational evidence suggests that the Sagittarius dwarf galaxy represents the only major ongoing accretion event in the Galactic halo, accounting for the majority of stellar debris identified there. This paper summarizes the recent discovery of another potential Milky Way accretion event, the Canis Major dwarf galaxy. This dwarf satellite galaxy is found to lie just below the Galactic plane and appears to be on an equatorial orbit. Unlike Sagittarius, which is contributing to the Galactic halo, the location and eventual demise of Canis Major suggests that it represents a building block of the thick disk.Comment: Refereed contribution to "Structure & Dynamics in the Local Universe, a workshop to honour Brent Tully's 60th birthday", Nov 2003. 4 pages + 2 figures (quality reduced due to size restrictions). To appear in PAS

The Divine Action Project, 1988–2003

This article explores the state of the art in theories of special divine action by means of a study of the Divine Action Project (DAP) co-sponsored by the Vatican Observatory and the Center for Theology and the Natural Sciences in Berkeley. The basic aim is to introduce the DAP and to summarize its results, especially as these were compiled in the final “capstone” meeting of the DAP, and drawing on the published output of the project where possible. The subsidiary aim is to evaluate criticisms of theories of special divine action developed within the DAP.ye

Duality, Equivalence, Mass and The Quest For The Vacuum

I contemplate the possibility that the mismatch between the maximally symmetric point (the free fermionic point) and the strictly self-dual point in the Narain moduli space plays a role in the string vacuum selection. The role of self-duality in the recent formulation of quantum mechanics from an equivalence postulate, and the new perspective that it offers on the foundations of quantum gravity and the origin of mass, are discussed.Comment: 8 pages. Standard Latex & sprocl.tex. Invited talk presented at PASCOS 99, Lake Tahoe, CA December 10-16 199