284 research outputs found
Atlas of Science Collaboration, 1971-2020
The evolving landscape of interinstitutional collaborative research across 15
natural science disciplines is explored using the open data sourced from
OpenAlex. This extensive exploration spans the years from 1971 to 2020,
facilitating a thorough investigation of leading scientific output producers
and their collaborative relationships based on coauthorships. The findings are
visually presented on world maps and other diagrams, offering a clear and
insightful portrayal of notable variations in both national and international
collaboration patterns across various fields and time periods. These visual
representations serve as valuable resources for science policymakers, diplomats
and institutional researchers, providing them with a comprehensive overview of
global collaboration and aiding their intuitive grasp of the evolving nature of
these partnerships over time.Comment: 6+121 pages, many figures, 49 M
A half-century of international research collaboration dynamism: Congregate or disperse?
The past decades have witnessed a dramatic change in researchers'
collaboration mode across borders. In addition to purely academia-driven
collaborations, various state-led initiatives have also been developed and are
underway, reflecting the rapidly changing geopolitical situation of the
contemporary world. In such multilayered cooperative and competitive
relationships among countries, it is of great interest to leaders in academia
and the policy arena to grasp the full scope of international research
collaboration and their country's place within it, along with its change over
time. However, evidence for such world-scale dynamism is scarce to date. This
paper provides unique evidence of how international collaboration clusters have
formed and evolved over the past half-century for a broad set of scientific
publications. Our analyses are based on data retrieved from OpenAlex, a
large-scale Open Bibliometrics platform launched in 2022. The science and
technology areas of focus include Quantum Science, Artificial Intelligence,
Biotechnology and others, totalling 15. We first review the top-tier countries'
global presence change for each discipline, measured by publication volumes and
international collaboration rates. Notably, the US and China are shown to have
rapidly moved closer together for decades but have started moving apart after
2019. Subsequently, we analyse and visualise the international collaboration
clusters for each discipline and period based on a hierarchical clustering
method. Finally, we provide global-scale quantitative evidence for a 'Shrinking
World' of the past half-century's research collaboration. These results provide
valuable insights into the big picture of past, present and future
international collaboration.Comment: 2+19 pages (5 figures) for Main Text; 21 pages (7 figures, 1 table)
for Supplementary Material
Large Winding Sector of AdS/CFT
We study a family of classical strings on R x S^3 subspace of the AdS_5 x S^5
background that interpolates between pulsating strings and single-spike
strings. They are obtained from the helical strings of hep-th/0609026 by
interchanging worldsheet time and space coordinates, which maps
rotating/spinning string states with large spins to oscillating states with
large winding numbers. From a finite-gap perspective, this transformation is
realised as an interchange of quasi-momentum and quasi-energy defined for the
algebraic curve. The gauge theory duals are also discussed, and are identified
with operators in the non-holomorphic sector of N=4 super Yang-Mills. They can
be viewed as excited states above the ``antiferromagnetic'' state, which is
``the farthest from BPS'' in the spin-chain spectrum. Furthermore, we
investigate helical strings on AdS_3 x S^1 in an appendix.Comment: 1+52 pages, 10 figures, v2: references and comments added, v3: minor
changes and a reference adde
Evolving landscape of US-China science collaboration: Convergence and divergence
International research collaboration among global scientific powerhouses has
exhibited a discernible trend towards convergence in recent decades. Notably,
the US and China have significantly fortified their collaboration across
diverse scientific disciplines, solidifying their status as a national-level
duopoly in global scientific knowledge production. However, recent reports hint
at a potential decline in collaboration between these two giants, even amidst
the backdrop of advancing global convergence. Understanding the intricate
interplay between cooperation and disparity within the US-China relationship is
vital for both academia and policy leaders, as it provides invaluable insights
into the potential future trajectory of global science collaboration. Despite
its significance, there remains a noticeable dearth of quantitative evidence
that adequately encapsulates the dynamism across disciplines and over time. To
bridge this knowledge gap, this study delves into the evolving landscape of
interaction between the US and China over recent decades. This investigation
employs two approaches, one based on paper identifiers and the other on
researcher identifiers, both obtained from bibliometric data sourced from
OpenAlex. From both approaches, our findings unveil the unique and dynamic
nature of the US-China relationship, characterised by a collaboration pattern
initially marked by rapid convergence, followed by a recent phase of
divergence.Comment: Main Text: 15 pages (4 figures); Supplementary Materials: 3 pages (3
figures
Dynamics of moire trion and its valley polarization in microfabricated WSe2/MoSe2 heterobilayer
The moire potential, induced by stacking two monolayer semiconductors with
slightly different lattice mismatches, acts as periodic quantum confinement for
optically generated excitons, resulting in spatially ordered zero-dimensional
quantum systems. However, there are limitations to exploring intrinsic optical
properties of moire excitons due to ensemble averaged and broadened emissions
from many peaks caused by the inhomogeneity of the moire potential. In this
study, we proposed a microfabrication technique based on focused Ga+ ion beams,
which enables us to control the number of peaks originating from the moire
potential and thus explore unknown moire optical characteristics of WSe2/MoSe2
heterobilayers. By taking advantage of this approach, we reveal emissions from
a single moire exciton and charged moire exciton (trion) under electrostatic
doping conditions. We show the momentum dark moire trion state above the bright
trion state with a splitting energy of approximately 4 meV and clarify that the
dynamics are determined by the initial trion population in the bright state.
Furthermore, the degree of negative circularly polarized emissions and their
valley dynamics of moire trions are dominated by a very long valley relaxation
process lasting ~700 ns. Our findings on microfabricated heterobilayers could
be viewed as an extension of our groundbreaking efforts in the field of quantum
optics application using moire superlattices.Comment: 41 pages, 4 figure
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