Suppression of maximal linear gluon polarization in angular asymmetries

We perform a phenomenological analysis of the $\cos 2 \phi$ azimuthal asymmetry in virtual photon plus jet production induced by the linear polarization of gluons in unpolarized $pA$ collisions. Although the linearly polarized gluon distribution becomes maximal at small $x$, TMD evolutionleads to a Sudakov suppression of the asymmetry with increasing invariant mass of the $\gamma^*$-jet pair. Employing a small-$x$ model input distribution, the asymmetry is found to be strongly suppressed under TMD evolution, but still remains sufficiently large to be measurable in the typical kinematical region accessible at RHIC or LHC at moderate photon virtuality, whereas it is expected to be negligible in $Z/W$-jet pair production at LHC. We point out the optimal kinematics for RHIC and LHC studies, in order to expedite the first experimental studies of the linearly polarized gluon distribution through this process. We further argue that this is a particularly clean process to test the $k_t$-resummation formalism in the small-$x$ regime.Comment: 11 pages, 6 figure

Gravity Waves as a Probe of Hubble Expansion Rate During An Electroweak Scale Phase Transition

Just as big bang nucleosynthesis allows us to probe the expansion rate when the temperature of the universe was around 1 MeV, the measurement of gravity waves from electroweak scale first order phase transitions may allow us to probe the expansion rate when the temperature of the universe was at the electroweak scale. We compute the simple transformation rule for the gravity wave spectrum under the scaling transformation of the Hubble expansion rate. We then apply this directly to the scenario of quintessence kination domination and show how gravity wave spectra would shift relative to LISA and BBO projected sensitivities.Comment: 28 pages, 2 figures

Planets in Spin-Orbit Misalignment and the Search for Stellar Companions

The discovery of giant planets orbiting close to their host stars was one of the most unexpected results of early exoplanetary science. Astronomers have since found that a significant fraction of these 'Hot Jupiters' move on orbits substantially misaligned with the rotation axis of their host star. We recently reported the measurement of the spin-orbit misalignment for WASP-79b by using data from the 3.9 m Anglo-Australian Telescope. Contemporary models of planetary formation produce planets on nearly coplanar orbits with respect to their host star's equator. We discuss the mechanisms which could drive planets into spin-orbit misalignment. The most commonly proposed being the Kozai mechanism, which requires the presence of a distant, massive companion to the star-planet system. We therefore describe a volume-limited direct-imaging survey of Hot Jupiter systems with measured spin-orbit angles, to search for the presence of stellar companions and test the Kozai hypothesis.Comment: Accepted for publication in the peer-reviewed proceedings of the 13th annual Australian Space Science Conferenc

The effect of allophonic variability on L2 contrast perception: Evidence from perception of English vowels

Current frameworks of L2 phonetic acquisition remain largely underspecified with respect to the role of L1 allophonic variability in acquisition. Examining the role of L1 allophonic variability, the current study compared the perceptual discrimination of English /i-I/ and /E-æ/ by L1 Korean and L1 Mandarin speakers. Korean and Mandarin vowel inventories differ in that Mandarin employs significantly greater allophonic variation of the mid-region /E/ vowel. Results demonstrated worse perceptual accuracy by L1 Mandarin speakers for the /E-æ/ contrast than L1 Korean speakers. These results suggest that both L1 phonemic inventories and allophonic variation play a role in L2 phonetic acquisition

Quantifying the Roles of Visual, Linguistic, and Visual-Linguistic Complexity in Verb Acquisition

Children typically learn the meanings of nouns earlier than the meanings of verbs. However, it is unclear whether this asymmetry is a result of complexity in the visual structure of categories in the world to which language refers, the structure of language itself, or the interplay between the two sources of information. We quantitatively test these three hypotheses regarding early verb learning by employing visual and linguistic representations of words sourced from large-scale pre-trained artificial neural networks. Examining the structure of both visual and linguistic embedding spaces, we find, first, that the representation of verbs is generally more variable and less discriminable within domain than the representation of nouns. Second, we find that if only one learning instance per category is available, visual and linguistic representations are less well aligned in the verb system than in the noun system. However, in parallel with the course of human language development, if multiple learning instances per category are available, visual and linguistic representations become almost as well aligned in the verb system as in the noun system. Third, we compare the relative contributions of factors that may predict learning difficulty for individual words. A regression analysis reveals that visual variability is the strongest factor that internally drives verb learning, followed by visual-linguistic alignment and linguistic variability. Based on these results, we conclude that verb acquisition is influenced by all three sources of complexity, but that the variability of visual structure poses the most significant challenge for verb learning