Two-flavor QCD at finite temperature and chemical potential in a functional approach

We summarize recent results obtained in the Dyson-Schwinger formalism to study the chiral and deconfinement phase transitions of quenched and unquenched QCD at finite temperature and chemical potential. In the quenched case we compare SU(2) and SU(3) gauge theories by taking lattice data for the gluon as an input for the quark Dyson-Schwinger equation. As compared to previous investigations we find a clearer distinction between the second order transition of the two-color theory and the (weak) first order transition of the three-color gauge theory. We then extend this study to unquenched QCD at finite chemical potential by taking matter effects to the gluon into account and investigate the order of the chiral phase transition and the behavior of the deconfinement transition. What we find are coinciding phase transitions up to a critical endpoint which is located at large chemical potential.Comment: 7 pages, 5 figures, contribution to the proceedings of the International School of Nuclear Physics, Erice 201

Debt Financing of High-growth Startups

We study the business model of venture debt firms, specialized institutions that provide loans to high-growth startups. Venture debt represents an apparent contradiction with traditional debt theory since startups have negative cash flows and lack tangible assets to secure the loan. Yet, we estimate that the U.S. venture debt industry provides at least one venture debt dollar for every seven venture capital dollars invested. We aim to provide the first empirical evidence on the determinants of the lending decision. Building on existing field interviews and case studies, we design a choice experiment of the lending decision and conduct experiments with 55 senior venture lenders. We find support for the hypothesis that backing by venture capital firms substitutes for startups’ cash flow. Furthermore, we illustrate the signaling effect of patents and their role as collateral to facilitate the lending decision.Venture capital; startups; patents

A4A_4 symmetry at colliders and in the universe

Two puzzling facts of our time are the observed patterns in the fermion masses and mixings and the existence of non-baryonic dark matter, which are both often associated with extensions of the Standard Model at higher energy scales. In this paper, we consider a solution to these two problems with the flavour symmetry ${\mathbb A}_4\times {\mathbb Z}_2\times {\mathbb Z}_2^\prime$, in a model which has been shown before to explain large leptonic mixings with a specific texture. The model contains 3 generations of $SU(2)_L$-doublet scalar fields, arranged as an ${\mathbb A}_4$-triplet, that spontaneously break the electroweak symmetry, and a "dark sector" of ${\mathbb Z}_2$-odd fields, containing one Majorana neutrino and an ${\mathbb A}_4$-triplet $SU(2)_L$-doublet scalar field, the lightest of which provides a candidate for dark matter. Concerning the ${\mathbb Z}_2$-even scalar fields, compared to the Standard Model, we predict additional fields with masses at the electroweak scale. We therefore investigate present phenomenological constraints from lepton flavour violation experiments, obtaining a lower bound on the extra scalar masses of 140 GeV. Furthermore we consider the oblique parameters, Higgs boson decay properties and possible flavour violating signals at the LHC. Concerning the "dark sector", we study bounds from dark matter search experiments and identify the parameter space of the dark matter candidate that is compatible with the observed relic density. We find two allowed mass ranges for the dark matter within which the experimental constraints can be accommodated: the low-mass range is from 47 GeV to 74 GeV and the high-mass range is from 600 GeV and 3.6 TeV.Comment: v2, to be published in JHE

JPEG2000 Image Compression on Solar EUV Images

For future solar missions as well as ground-based telescopes, efficient ways to return and process data have become increasingly important. Solar Orbiter, e.g., which is the next ESA/NASA mission to explore the Sun and the heliosphere, is a deep-space mission, which implies a limited telemetry rate that makes efficient onboard data compression a necessity to achieve the mission science goals. Missions like the Solar Dynamics Observatory (SDO) and future ground-based telescopes such as the Daniel K. Inouye Solar Telescope, on the other hand, face the challenge of making petabyte-sized solar data archives accessible to the solar community. New image compression standards address these challenges by implementing efficient and flexible compression algorithms that can be tailored to user requirements. We analyse solar images from the Atmospheric Imaging Assembly (AIA) instrument onboard SDO to study the effect of lossy JPEG2000 (from the Joint Photographic Experts Group 2000) image compression at different bit rates. To assess the quality of compressed images, we use the mean structural similarity (MSSIM) index as well as the widely used peak signal-to-noise ratio (PSNR) as metrics and compare the two in the context of solar EUV images. In addition, we perform tests to validate the scientific use of the lossily compressed images by analysing examples of an on-disk and off-limb coronal-loop oscillation time-series observed by AIA/SDO.Comment: 25 pages, published in Solar Physic

New Results on Quantum Property Testing

We present several new examples of speed-ups obtainable by quantum algorithms in the context of property testing. First, motivated by sampling algorithms, we consider probability distributions given in the form of an oracle $f:[n]\to[m]$. Here the probability \PP_f(j) of an outcome $j\in[m]$ is the fraction of its domain that $f$ maps to $j$. We give quantum algorithms for testing whether two such distributions are identical or $\epsilon$-far in $L_1$-norm. Recently, Bravyi, Hassidim, and Harrow \cite{BHH10} showed that if \PP_f and \PP_g are both unknown (i.e., given by oracles $f$ and $g$), then this testing can be done in roughly $\sqrt{m}$ quantum queries to the functions. We consider the case where the second distribution is known, and show that testing can be done with roughly $m^{1/3}$ quantum queries, which we prove to be essentially optimal. In contrast, it is known that classical testing algorithms need about $m^{2/3}$ queries in the unknown-unknown case and about $\sqrt{m}$ queries in the known-unknown case. Based on this result, we also reduce the query complexity of graph isomorphism testers with quantum oracle access. While those examples provide polynomial quantum speed-ups, our third example gives a much larger improvement (constant quantum queries vs polynomial classical queries) for the problem of testing periodicity, based on Shor's algorithm and a modification of a classical lower bound by Lachish and Newman \cite{lachish&newman:periodicity}. This provides an alternative to a recent constant-vs-polynomial speed-up due to Aaronson \cite{aaronson:bqpph}.Comment: 2nd version: updated some references, in particular to Aaronson's Fourier checking proble

Knowledge convergence in collaborative learning

In collaborative learning the question has been raised as to how learners in small groups influence one another and converge or diverge with respect to knowledge. Knowledge convergence can be conceptualised as knowledge equivalence and as shared knowledge prior to, during, and subsequent to collaborative learning. Knowledge equivalence refers to learners becoming more similar to their learning partners with regard to the extent of their individual knowledge. Shared knowledge means that learners have knowledge on the very same concepts as their learning partners. In this article, we provide measures for assessing both, knowledge equivalence and shared knowledge

Spread and Control of Rift Valley Fever virus after accidental introduction in the Netherlands: a modelling study.

Rift Valley Fever (RVF) is a zoonotic vector-borne infection and causes a potentially severe disease in both humans and young animals. The Ministry of Economic Affairs, Agriculture and Innovation (EL&I) is interested in the risk of an outbreak of Rift Valley Fever virus (RVFV) for the Netherlands, and more knowledge is needed about the risk of introduction of the virus, the risk of spread (transmission) of the virus in the country once introduced, and the methods for control and surveillance. For this purpose, a mathematical model was developed to study (1) the probability of a RVF outbreak at different days of introduction during the year, (2) the probability of persistence of the infection during the entire year, and (3) outbreak size and duration at different days of introduction during the year