Primordial Galaxy Formation and IGM Reionization

In this talk I will present a model for primordial galaxy formation. In particular, I will review the feedback effects that regulate the process: (i) radiative (i.e. ionizing and H_2-photodissociating photons) and (ii) stellar (i.e. SN explosions) feedback produced by massive stars. I will show the results of a model for galaxy formation and IGM reionization, which includes a self-consistent treatment of the above feedback effects. Finally, I will describe a Monte Carlo method for the radiative transfer of ionizing photons through the IGM and discuss its application to the IGM reionization problem.Comment: 4 pages, 3 figures. To appear in "A New Era in Cosmology", (ASP Conference Proceedings), eds. T. Shanks and N. Metcalf

Effects of hanyu pinyin on pronunciation in learners of Chinese as a foreign language

This paper provides evidence that the hanyu pinyin representation of the phonology of Chinese affects the production of Chinese phonology in instructed learners of Chinese as a Foreign Language. Pinyin generally has a one-to-one correspondence between graphemes and phonemes, but its transcription of some Chinese rimes does not represent the main vowel. As a consequence, learners of Chinese as a Foreign Language have non-target-like phonological representations of Chinese rimes, which in turn lead to non-target-like pronunciations. A hanzi reading-aloud task was used to elicit syllables containing the three rimes /iou/, /uei/ and /uən/ from final-year CFL students. Results show that learners often delete the vowels that are not represented in the pinyin transcription, but they produce the same vowels in the same rimes when the pinyin transcription represents them. It is concluded that the pinyin orthographic input interacts with the phonological input in shaping the phonological representations and pronunciation of Chinese syllables in intermediate as well as beginner CFL learners. Language teachers should therefore be aware of the effects of the pinyin orthography

Orthographic input and phonological representations in learners of Chinese as a foreign language.

This paper provides evidence that the second language orthographic input affects the mental representations of L2 phonology in instructed beginner L2 learners. Previous research has shown that orthographic representations affect monolinguals' performance in phonological awareness tasks; in instructed L2 learners such representations could also affect pronunciation. This study looked at the phonological representations of Chinese rimes in beginner learners of Chinese as a foreign language, using a phoneme counting task and a phoneme segmentation task. Results show that learners do not count or segment the main vowel in those syllables where it is not represented in the pinyin (romanisation) orthographic representations. It appears that the pinyin orthographic input is reinterpreted according to L1 phonology-orthography correspondences, and interacts with the phonological input in shaping the phonological representations of Chinese syllables in beginner learners. This explains previous findings that learners of Chinese do not pronounce the main vowel in these syllables

Unbounded critical points for a class of lower semicontinuous functionals

In this paper we prove existence and multiplicity results of unbounded critical points for a general class of weakly lower semicontinuous functionals. We will apply a suitable nonsmooth critical point theory

A p-Laplacian supercritical Neumann problem

For $p>2$, we consider the quasilinear equation $-\Delta_p u+|u|^{p-2}u=g(u)$ in the unit ball $B$ of $\mathbb R^N$, with homogeneous Neumann boundary conditions. The assumptions on $g$ are very mild and allow the nonlinearity to be possibly supercritical in the sense of Sobolev embeddings. We prove the existence of a nonconstant, positive, radially nondecreasing solution via variational methods. In the case $g(u)=|u|^{q-2}u$, we detect the asymptotic behavior of these solutions as $q\to\infty$.Comment: 34 pages, 1 figur

Binary Hypothesis Testing Game with Training Data

We introduce a game-theoretic framework to study the hypothesis testing problem, in the presence of an adversary aiming at preventing a correct decision. Specifically, the paper considers a scenario in which an analyst has to decide whether a test sequence has been drawn according to a probability mass function (pmf) P_X or not. In turn, the goal of the adversary is to take a sequence generated according to a different pmf and modify it in such a way to induce a decision error. P_X is known only through one or more training sequences. We derive the asymptotic equilibrium of the game under the assumption that the analyst relies only on first order statistics of the test sequence, and compute the asymptotic payoff of the game when the length of the test sequence tends to infinity. We introduce the concept of indistinguishability region, as the set of pmf's that can not be distinguished reliably from P_X in the presence of attacks. Two different scenarios are considered: in the first one the analyst and the adversary share the same training sequence, in the second scenario, they rely on independent sequences. The obtained results are compared to a version of the game in which the pmf P_X is perfectly known to the analyst and the adversary

Nodal sets of magnetic Schroedinger operators of Aharonov-Bohm type and energy minimizing partitions

In this paper we consider a stationary Schroedinger operator in the plane, in presence of a magnetic field of Aharonov-Bohm type with semi-integer circulation. We analyze the nodal regions for a class of solutions such that the nodal set consists of regular arcs, connecting the singular points with the boundary. In case of one magnetic pole, which is free to move in the domain, the nodal lines may cluster dissecting the domain in three parts. Our main result states that the magnetic energy is critical (with respect to the magnetic pole) if and only if such a configuration occurs. Moreover the nodal regions form a minimal 3-partition of the domain (with respect to the real energy associated to the equation), the configuration is unique and depends continuously on the data. The analysis performed is related to the notion of spectral minimal partition introduced in [20]. As it concerns eigenfunctions, we similarly show that critical points of the Rayleigh quotient correspond to multiple clustering of the nodal lines.Comment: 32 page