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The clock is ticking! Executive temporal depth, industry velocity, and competitive aggressiveness
We examine how the interplay between executive temporal depth (time horizons that executives consider when contemplating past and future events) and industry velocity (the rate at which new opportunities emerge and disappear in an industry) shapes competitive aggressiveness (a firm's propensity to challenge rivals directly and intensely in order to maintain or improve its market position) and firm performance. Based on panel data (from 1995 to 2000) from 258 firms in 23 industries, we found that executive temporal depth exhibited different patterns of relationships with competitive aggressiveness in low- and high-velocity industries. Moreover, competitive aggressiveness had a positive main effect on firm performance, but this effect was stronger in high-velocity industries than in low-velocity industries
Asymptotic Behavior of the Correlator for Polyakov Loops
The asymptotic behavior of the correlator for Polyakov loop operators
separated by a large distance is determined for high temperature QCD. It is
dominated by nonperturbative effects related to the exchange of magnetostatic
gluons. To analyze the asymptotic behavior, the problem is formulated in terms
of the effective field theory of QCD in 3 space dimensions. The Polyakov loop
operator is expanded in terms of local gauge-invariant operators constructed
out of the magnetostatic gauge field, with coefficients that can be calculated
using resummed perturbation theory. The asymptotic behavior of the correlator
is , where is the mass of the lowest-lying glueball in
-dimensional QCD. This result implies that existing lattice calculations
of the Polyakov loop correlator at the highest temperatures available do not
probe the true asymptotic region in .Comment: 10 pages, NUHEP-TH-94-2
Monteverde: Ecology and Conservation of a Tropical Cloud Forest - 2014 Updated Chapters
The Monteverde Cloud Forest Reserve has captured the worldwide attention of biologists, conservationists, and ecologists and has been the setting for extensive investigation over the past 40 years. Roughly 40,000 ecotourists visit the Cloud Forest each year, and it is often considered the archetypal high-altitude rain forest. âMonteverde: Ecology and Conservation of a Tropical Cloud Forestâ, edited by Nalini Nadkarni and Nathaniel T. Wheelwright (Oxford University Press, 2000 and Bowdoinâs Scholarâs Bookshelf. Book 1 ), features synthetic chapters and specific accounts written by more than 100 biologist and local residents, presenting in a single volume everything known in 2000 about the biological diversity of Monteverde, Costa Rica, and how to protect it. The new short chapters written in 2014 by original contributors, and presented here update and expand that knowledge through 2014.https://digitalcommons.bowdoin.edu/scholars-bookshelf/1004/thumbnail.jp
Ants mediate the structure of phytotelm communities in an ant-garden bromeliad
The main theories explaining the biological diversity of rain forests often confer a limited understanding of the contribution of interspecific interactions to the observed patterns. We show how two-species mutualisms can affect much larger segments of the invertebrate community in tropical rain forests. Aechmea mertensii (Bromeliaceae) is both a phytotelm (plant-held water) and an ant-garden epiphyte. We studied the influence of its associated ant species (Pachycondyla goeldii and Camponotus femoratus) on the physical characteristics of the plants, and, subsequently, on the diversity of the invertebrate communities that inhabit their tanks. As dispersal agents for the bromeliads, P. goeldii and C. femoratus influence the shape and size of the bromeliad by determining the location of the seedling, from exposed to partially shaded areas. By coexisting on a local scale, the two ant species generate a gradient of habitat conditions in terms of available resources (space and food) for aquatic invertebrates, the diversity of the invertebrate communities increasing with greater volumes of water and fine detritus. Two-species mutualisms are widespread in nature, but their influence on the diversity of entire communities remains largely unexplored. Because macroinvertebrates constitute an important part of animal production in all ecosystem types, further investigations should address the functional implications of such indirect effects
3d SU(N) + adjoint Higgs theory and finite temperature QCD
We study to what extent the three-dimensional SU(N)+adjoint Higgs theory can
be used as an effective theory for finite temperature SU(N) gauge theory, with
N=2,3. The parameters of the 3d theory are computed in 2-loop perturbation
theory in terms of T/Lambda_MSbar,N,N_f. The perturbative effective potential
of the 3d theory is computed to two loops for N=2. While the Z(N) symmetry
probably driving the 4d confinement-deconfinement phase transition (for N_f=0)
is not explicit in the effective Lagrangian, it is partly reinstated by
radiative effects in the 3d theory. Lattice simulations in the 3d theory are
carried out for N=2, and the static screening masses relevant for the
high-temperature phase of the 4d theory are measured. In particular, we measure
non-perturbatively the O(g^2 T) correction to the Debye screening mass. We find
that non-perturbative effects are much larger in the SU(2) + adjoint Higgs
theory than in the SU(2) + fundamental Higgs theory.Comment: 30 pages, 9 figure
On the Phase Diagram of the SU(2) Adjoint Higgs Model in 2+1 Dimensions
The phase diagram is investigated for SU(2) lattice gauge theory in d=3,
coupled to adjoint scalars. For small values of the quartic scalar coupling,
lambda, the transition separating Higgs and confinement phases is found to be
first-order, in agreement with earlier work by Nadkarni. The surface of
second-order transitions conjectured by Nadkarni, however, is shown instead to
correspond to crossover behaviour. This conclusion is based on a finite size
analysis of the scalar mass and susceptibility. The nature of the phase
transition at the termination of first-order behaviour is investigated and we
find evidence for a critical point at which the scalar mass vanishes. The
photon mass and confining string tension are measured and are found to be
negligibly small in the Higgs phase. This is correlated with the very small
density of magnetic monopoles in the Higgs phase. The string tension and photon
mass rise rapidly as the crossover is traversed towards the symmetric phase.Comment: LaTeX. Replaced with version to be published in Physics Letters B.
Minor changes onl
Effective Field Theory Approach to High-Temperature Thermodynamics
An effective field theory approach is developed for calculating the
thermodynamic properties of a field theory at high temperature and weak
coupling . The effective theory is the 3-dimensional field theory obtained
by dimensional reduction to the bosonic zero-frequency modes. The parameters of
the effective theory can be calculated as perturbation series in the running
coupling constant . The free energy is separated into the contributions
from the momentum scales and , respectively. The first term can be
written as a perturbation series in . If all forces are screened at the
scale , the second term can be calculated as a perturbation series in
beginning at order . The parameters of the effective theory satisfy
renormalization group equations that can be used to sum up leading logarithms
of . We apply this method to a massless scalar field with a
interaction, calculating the free energy to order and the
screening mass to order .Comment: 40 pages, LaTeX, 5 uuecoded figure
Next-to-leading Order Debye Mass for the Quark-gluon Plasma
The Debye screening mass for a quark-gluon plasma at high temperature is
calculated to next-to-leading order in the QCD coupling constant from the
correlator of two Polyakov loops. The result agrees with the screening mass
defined by the location of the pole in the gluon propagator as calculated by
Rebhan. It is logarithmically sensitive to nonperturbative effects associated
with the screening of static chromomagnetic fields.Comment: 8 pages, NUHEP-TH-94-1
Polyakov Loop Dynamics in the Center Symmetric Phase
A study of the center symmetric phase of SU(2) Yang Mills theory is
presented. Realization of the center symmetry is shown to result from
non-perturbative gauge fixing. Dictated by the center symmetry, this phase
exhibits already at the perturbative level confinement like properties. The
analysis is performed by investigating the dynamics of the Polyakov loops. The
ultralocality of these degrees of freedom implies significant changes in the
vacuum structure of the theory. General properties of the confined phase and of
the transition to the deconfined phase are discussed. Perturbation theory built
upon the vacuum of ultralocal Polyakov loops is presented and used to
calculate, via the Polyakov loop correlator, the static quark-antiquark
potential.Comment: 45 pages, LaTeX, 8 figure
Non-perturbative formulation of the static color octet potential
By dressing Polyakov lines with appropriate functionals of the gauge fields,
we construct observables describing a fundamental representation static
quark-antiquark pair in the singlet, adjoint and average channels of SU(N) pure
gauge theory. Each of the potentials represents a gauge invariant eigenvalue of
the Hamiltonian. Numerical simulations are performed for SU(2) in 2+1
dimensions. The adjoint channel is found to be repulsive at small and confining
at large separations, suggesting the existence of a metastable (N^2-1)-plet
bound state. For small distances and temperatures above the deconfinement
transition, the leading order perturbative prediction for the ratio of singlet
and adjoint potentials is reproduced by the lattice data.Comment: 10 pages, 3 figure
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