249 research outputs found
Animal linguistics: Exploring referentiality and compositionality in bird calls
Establishing the theory of language evolution is an ongoing challenge in science. One profitable approach in this regard is to seek the origins of linguistic capabilities by comparing language with the vocal communication systems of closely related relatives (i.e., the great apes). However, several key capabilities of language appear to be absent in non-human primates, which limits the range of studies, such as direct phylogenetic comparison. A further informative approach lies in identifying convergent features in phylogenetically distant animals and conducting comparative studies. This approach is particularly useful with respect to establishing general rules for the evolution of linguistic capabilities. In this article, I review recent findings on linguistic capabilities in a passerine bird species, the Japanese tit (Parus minor). Field experiments have revealed that Japanese tits produce unique alarm calls when encountering predatory snakes, which serve to enhance the visual attention of call receivers with respect to snake-like objects. Moreover, tits often combine discrete types of meaningful calls into fixed-ordered sequences according to an ordering rule, conveying a compositional message to receivers. These findings indicate that two core capabilities of language, namely, referentiality and compositionality, have independently evolved in the avian lineage. I describe how these linguistic capabilities can be examined under field conditions and discuss how such research may contribute to exploring the origins and evolution of language
Experimental evidence for core-Merge in the vocal communication system of a wild passerine
シジュウカラに言語の核:2語を1つにまとめる力(併合)を確認. 京都大学プレスリリース. 2022-09-29.One of the cognitive capacities underlying language is core-Merge, which allows senders to combine two words into a sequence and receivers to recognize it as a single unit. Recent field studies suggest intriguing parallels in non-human animals, e.g., Japanese tits (Parus minor) combine two meaning-bearing calls into a sequence when prompting antipredator displays in other individuals. However, whether such examples represent core-Merge remains unclear; receivers may perceive a two-call sequence as two individual calls that are arbitrarily produced in close time proximity, not as a single unit. If an animal species has evolved core-Merge, its receivers should treat a two-call sequence produced by a single individual differently from the same two calls produced by two individuals with the same timing. Here, we show that Japanese tit receivers exhibit antipredator displays when perceiving two-call sequences broadcast from a single source, but not from two sources, providing evidence for core-Merge in animals
Neutrino oscillation and expected event rate of supernova neutrinos in adiabatic explosion model
We study how the influence of the shock wave appears in neutrino oscillations
and the neutrino spectrum using density profile of adiabatic explosion model of
a core-collapse supernova which is calculated in an implicit Lagrangian code
for general relativistic spherical hydrodynamics. We calculate expected event
rates of neutrino detection at SK and SNO for various theta_{13} values and
both normal and inverted hierarchies. The predicted event rates of bar{nu}_e
and nu_e depend on the mixing angle theta_{13} for the inverted and normal
hierarchies, respectively, and the influence of the shock appears for about 2 -
8 s when sin^2 2 theta_{13} is larger than 10^{-3}. These neutrino signals for
the shock propagation is decreased by < 30 % for bar{nu}_e in inverted (SK) or
by < 15 % for nu_e in normal hierarchy (SNO) compared with the case without
shock. The obtained ratio of the total event for high-energy neutrinos (20 MeV
< E_{nu} < 60 MeV) to low-energy neutrinos (5 MeV < E_{nu} < 20 MeV) is
consistent with the previous studies in schematic semi-analytic or other
hydrodynamic models of the shock propagation. The time dependence of the
calculated ratio of the event rates of high-energy to low-energy neutrinos is a
very useful observable which is sensitive to theta_{13} and hierarchies.
Namely, time-dependent ratio shows clearer signal of the shock propagation that
exhibits remarkable decrease by at most factor \sim 2 for bar{nu}_e in inverted
(SK), whereas it exhibits smaller change by \sim 10 % for nu_e in normal
hierarchy (SNO). Observing time-dependent high-energy to low-energy ratio of
the neutrino events thus would provide a piece of very useful information to
constrain theta_{13} and mass hierarchy, and eventually help understanding the
propagation how the shock wave propagates inside the star.Comment: 19 pages, 9 figures, accepted for publication in Physical Review
Evolution of Beryllium and Boron in the Inhomogeneous Early Galaxy
A model of supernova-driven chemical evolution of the Galactic halo, recently
proposed by Tsujimoto, Shigeyama, & Yoshii (1999, ApJL, 519, 64), is extended
in order to investigate the evolution of light elements such as Be and B (BeB),
which are produced mainly through spallative reactions with Galactic cosmic
rays. In this model each supernova sweeps up the surrounding interstellar gas
into a dense shell and directly enriches it with ejecta which consist of heavy
elements produced in each Type II supernova with different progenitor masses.
We propose a two-component source for GCRs such that both interstellar gas and
fresh SN ejecta engulfed in the shell are accelerated by the shock wave. Our
model results include: (1) a prediction of the intrinsic scatter in BeB and
[Fe/H] abundances within the model, (2) a successful prediction of the observed
linear trend between BeB and [Fe/H], (3) a proposal for using BeB as a cosmic
clock, as an alternative to [Fe/H], and (4) a method for possibly constraining
the BBN model from future observations of metal-poor stars.Comment: 3 color figures in 7 pages, accepted by ApJ Letter
Neutrino Nucleus Reactions based on New Shell Model Hamiltonians
A new shell model Hamiltonian for p-shell nuclei which properly takes into
account important roles of spin-isospin interactions is used to obtain cross
sections of neutrino-^12C reactions induced by decay-at-rest (DAR) neutrinos as
well as supernona neutrinos. Branching ratios to various decay channels are
calculated by the Hauser-Feshbach theory. Neutrino-^4He reactions are also
investigated by using recent shell model Hamiltonians. The reaction cross
sections are found to be enhanced for both ^12C and ^4He compared with previous
calculations. As an interesting consequence of this, a possible enhancement of
the production yields of light elements, ^7Li and ^11B, during supernova
explosions is pointed out.Comment: 11 pages, 14 eps-figures, to be published in Physical Review C (in
press
Impact of New beta-decay Half-lives on r-process Nucleosynthesis
We investigate the effects of newly measured beta-decay half-lives on
r-process nucleosynthesis. These new rates were determined by recent
experiments at the radioactive isotope beam factory facility in the RIKEN
Nishina Center. We adopt an r-process nucleosynthesis environment based on a
magnetohydrodynamic supernova explosion model that includes strong magnetic
fields and rapid rotation of the progenitor. A number of the new beta-decay
rates are for nuclei on or near the r-process path, and hence they affect the
nucleosynthesis yields and time scale of the r-process. The main effect of the
newly measured beta-decay half-lives is an enhancement in the calculated
abundance of isotopes with mass number A = 110 -- 120 relative to calculated
abundances based upon beta-decay rates estimated with the finite-range droplet
mass model. This effect slightly alleviates, but does not fully explain, the
tendency of r-process models to underproduce isotopes with A = 110 -- 120
compared to the solar-system r-process abundances.Comment: 9 pages, 3 figures, 1 table, published in PR
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