8,139 research outputs found
Quantifying the impact of weak, strong, and super ties in scientific careers
Scientists are frequently faced with the important decision to start or
terminate a creative partnership. This process can be influenced by strategic
motivations, as early career researchers are pursuers, whereas senior
researchers are typically attractors, of new collaborative opportunities.
Focusing on the longitudinal aspects of scientific collaboration, we analyzed
473 collaboration profiles using an ego-centric perspective which accounts for
researcher-specific characteristics and provides insight into a range of
topics, from career achievement and sustainability to team dynamics and
efficiency. From more than 166,000 collaboration records, we quantify the
frequency distributions of collaboration duration and tie-strength, showing
that collaboration networks are dominated by weak ties characterized by high
turnover rates. We use analytic extreme-value thresholds to identify a new
class of indispensable `super ties', the strongest of which commonly exhibit
>50% publication overlap with the central scientist. The prevalence of super
ties suggests that they arise from career strategies based upon cost, risk, and
reward sharing and complementary skill matching. We then use a combination of
descriptive and panel regression methods to compare the subset of publications
coauthored with a super tie to the subset without one, controlling for
pertinent features such as career age, prestige, team size, and prior group
experience. We find that super ties contribute to above-average productivity
and a 17% citation increase per publication, thus identifying these
partnerships - the analog of life partners - as a major factor in science
career development.Comment: 13 pages, 5 figures, 1 Tabl
Easy and nearly simultaneous proofs of the Ergodic Theorem and Maximal Ergodic Theorem
We give a short proof of a strengthening of the Maximal Ergodic Theorem which
also immediately yields the Pointwise Ergodic Theorem.Comment: Published at http://dx.doi.org/10.1214/074921706000000266 in the IMS
Lecture Notes--Monograph Series
(http://www.imstat.org/publications/lecnotes.htm) by the Institute of
Mathematical Statistics (http://www.imstat.org
A step towards the Alekseevskii Conjecture
We provide a reduction in the classification problem for non-compact,
homogeneous, Einstein manifolds. Using this work, we verify the (Generalized)
Alekseevskii Conjecture for a large class of homogeneous spaces.Comment: 12 pages, proof of main result simplified, final version to appear in
Math. Annale
Investment and Capital Constraints: Repatriations Under the American Jobs Creation Act
The American Jobs Creation Act (AJCA) significantly lowered US firms' tax cost when accessing their unrepatriated foreign earnings. Using this temporary shock to the cost of internal financing, we examine the role of capital constraints in firms' investment decisions. Controlling for the capacity to repatriate foreign earnings under the AJCA, we find that a majority of the funds repatriated by capital constrained firms were allocated to approved domestic investment. While unconstrained firms account for a majority of repatriated funds, no increase in investment resulted. Contrary to other examinations of the AJCA, we find little change in leverage and equity payouts.
Isomorphism and embedding of Borel systems on full sets
A Borel system consists of a measurable automorphism of a standard Borel
space. We consider Borel embeddings and isomorphisms between such systems
modulo null sets, i.e. sets which have measure zero for every invariant
probability measure. For every t>0 we show that in this category there exists a
unique free Borel system (Y,S) which is strictly t-universal in the sense that
all invariant measures on Y have entropy <t, and if (X,T) is another free
system obeying the same entropy condition then X embeds into Y off a null set.
One gets a strictly t-universal system from mixing shifts of finite type of
entropy at least t by removing the periodic points and "restricting" to the
part of the system of entropy <t. As a consequence, after removing their
periodic points the systems in the following classes are completely classified
by entropy up to Borel isomorphism off null sets: mixing shifts of finite type,
mixing positive-recurrent countable state Markov chains, mixing sofic shifts,
beta shifts, synchronized subshifts, and axiom-A diffeomorphisms. In particular
any two equal-entropy systems from these classes are entropy conjugate in the
sense of Buzzi, answering a question of Boyle, Buzzi and Gomez.Comment: 17 pages, v2: correction to bibliograph
Patterns of remnant discrete symmetries
We analyze patterns of remnant discrete symmetries that arise from U(1)^N
theories by spontaneous breaking. We describe a simple, geometrical way to
understand these patterns and provide methods for identifying the discrete
symmetries and bringing them to the simplest possible form. Applications in GUT
and string model building are briefly discussed.Comment: 14 pages, 2 figures, a related Mathematica package can be downloaded
from http://einrichtungen.physik.tu-muenchen.de/T30e/codes/DiscreteBreaking
Germany’s Current Account and Trade Surpluses A Technical Debate Enters the Geopolitical Limelight. Bertelsmann Stiftung GED Study April 2018
During the past decade, macroeconomic imbalances – typified by countries’ surplus
or deficit of exports, currency, or capital – have moved to the fore of international
economic policy debates. Global events and developments, such as China’s
integration into the world economy, the 2008 financial crisis, and the Eurozone crisis,
have created, and in some cases, compounded longstanding trade and investment
asymmetries around the world. These imbalances have no single cause, but are fostered
and magnified by the competitiveness of a country’s industries, domestic demand,
corporate investment decisions, and tax and monetary policy, among other factors. In
recent years, the widening gaps in countries’ trade relationships have become highly
politicized, prompting policymakers to respond with measures ranging from formalized
monitoring to punitive tariffs
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