The Nature of Scientific Proof in the Age of Simulations

Is numerical mimicry a third way of establishing truth?Comment: Published in American Scientist: Volume 102, Number 3, Pages 174 to 177 (http://www.americanscientist.org/issues/pub/2014/3/the-nature-of-scientific-proof-in-the-age-of-simulations

A Cloudiness Index for Transiting Exoplanets Based on the Sodium and Potassium Lines: Tentative Evidence for Hotter Atmospheres Being Less Cloudy at Visible Wavelengths

We present a dimensionless index that quantifies the degree of cloudiness of the atmosphere of a transiting exoplanet. Our cloudiness index is based on measuring the transit radii associated with the line center and wing of the sodium or potassium line. In deriving this index, we revisited the algebraic formulae for inferring the isothermal pressure scale height from transit measurements. We demonstrate that the formulae of Lecavelier et al. and Benneke & Seager are identical: the former is inferring the temperature while assuming a value for the mean molecular mass and the latter is inferring the mean molecular mass while assuming a value for the temperature. More importantly, these formulae cannot be used to distinguish between cloudy and cloudfree atmospheres. We derive values of our cloudiness index for a small sample of 7 hot Saturns/Jupiters taken from Sing et al. We show that WASP-17b, WASP-31b and HAT-P-1b are nearly cloudfree at visible wavelengths. We find the tentative trend that more irradiated atmospheres tend to have less clouds consisting of sub-micron-sized particles. We also derive absolute sodium and/or potassium abundances $\sim 10^2$ cm$^{-3}$ for WASP-17b, WASP-31b and HAT-P-1b (and upper limits for the other objects). Higher-resolution measurements of both the sodium and potassium lines, for a larger sample of exoplanetary atmospheres, are needed to confirm or refute this trend.Comment: Accepted by ApJL. 6 pages, 1 figure, 2 table

Distinguishability and indistinguishability by LOCC

We show that a set of linearly independent quantum states $\{(U_{m,n}\otimes I)\rho ^{AB}(U_{m,n}^{\dagger}\otimes I)\}_{m,n=0}^{d-1}$, where $U_{m,n}$ are generalized Pauli matrices, cannot be discriminated deterministically or probabilistically by local operations and classical communications (LOCC). On the other hand, any $l$ maximally entangled states from this set are locally distinguishable if $l(l-1)\le 2d$. The explicit projecting measurements are obtained to locally discriminate these states. As an example, we show that four Werner states are locally indistinguishable.Comment: 5 page

Fast construction of FM-index for long sequence reads

Summary: We present a new method to incrementally construct the FM-index for both short and long sequence reads, up to the size of a genome. It is the first algorithm that can build the index while implicitly sorting the sequences in the reverse (complement) lexicographical order without a separate sorting step. The implementation is among the fastest for indexing short reads and the only one that practically works for reads of averaged kilobases in length. Availability and implementation: https://github.com/lh3/ropebwt2 Contact: [email protected]: 2 page