30,913 research outputs found
Mean field convergence of a model of multiple TCP connections through a buffer implementing RED
RED (Random Early Detection) has been suggested when multiple TCP sessions
are multiplexed through a bottleneck buffer. The idea is to detect congestion
before the buffer overflows by dropping or marking packets with a probability
that increases with the queue length. The objectives are reduced packet loss,
higher throughput, reduced delay and reduced delay variation achieved through
an equitable distribution of packet loss and reduced synchronization. Baccelli,
McDonald and Reynier [Performance Evaluation 11 (2002) 77--97] have proposed a
fluid model for multiple TCP connections in the congestion avoidance regime
multiplexed through a bottleneck buffer implementing RED. The window sizes of
each TCP session evolve like independent dynamical systems coupled by the queue
length at the buffer. The key idea in [Performance Evaluation 11 (2002) 77--97]
is to consider the histogram of window sizes as a random measure coupled with
the queue. Here we prove the conjecture made in [Performance Evaluation 11
(2002) 77--97] that, as the number of connections tends to infinity, this
system converges to a deterministic mean-field limit comprising the window size
density coupled with a deterministic queue.Comment: Published at http://dx.doi.org/10.1214/105051605000000700 in the
Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute
of Mathematical Statistics (http://www.imstat.org
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Getting By With The Advice Of Their Friends: Ceos' Advice Networks And Firms' Strategic Responses To Poor Performance
This paper theorizes that relatively poor firm performance can prompt chief executive officers (CEOs) to seek more advice from executives of other firms who are their friends or similar to them and less advice from acquaintances or dissimilar others and suggests how and why this pattern of advice seeking could reduce firms' propensity to change corporate strategy in response to poor performance. We test our hypotheses with large-sample survey data on the identities of CEOs' advice contacts and archival data on firm performance and corporate strategy. The results confirm our hypotheses and show that executives' social network ties can influence firms' responses to economic adversity, in particular by inhibiting strategic change in response to relatively poor firm performance. Additional findings indicate that CEOs' advice seeking in response to low performance may ultimately have negative consequences for subsequent performance, suggesting how CEOs' social network ties could play an indirect role in organizational decline and downward spirals in firm performance.Business Administratio
Z-Pencils
The matrix pencil (A,B) = {tB-A | t \in C} is considered under the
assumptions that A is entrywise nonnegative and B-A is a nonsingular M-matrix.
As t varies in [0,1], the Z-matrices tB-A are partitioned into the sets L_s
introduced by Fiedler and Markham. As no combinatorial structure of B is
assumed here, this partition generalizes some of their work where B=I. Based on
the union of the directed graphs of A and B, the combinatorial structure of
nonnegative eigenvectors associated with the largest eigenvalue of (A,B) in
[0,1) is considered.Comment: 8 pages, LaTe
Collide and Conquer: Constraints on Simplified Dark Matter Models using Mono-X Collider Searches
The use of simplified models as a tool for interpreting dark matter collider
searches has become increasingly prevalent, and while early Run II results are
beginning to appear, we look to see what further information can be extracted
from the Run I dataset. We consider three `standard' simplified models that
couple quarks to fermionic singlet dark matter: an -channel vector mediator
with vector or axial-vector couplings, and a -channel scalar mediator. Upper
limits on the couplings are calculated and compared across three alternate
channels, namely mono-jet, mono- (leptonic) and mono- (hadronic). The
strongest limits are observed in the mono-jet channel, however the
computational simplicity and absence of significant -channel model width
effects in the mono-boson channels make these a straightforward and competitive
alternative. We also include a comparison with relic density and direct
detection constraints.Comment: 32 pages, 8 figures; v2: minor changes, conclusion unchanged, matches
published versio
Thermodynamic constraints on the amplitude of quantum oscillations
Magneto-quantum oscillation experiments in high temperature superconductors
show a strong thermally-induced suppression of the oscillation amplitude
approaching critical dopings---in support of a quantum critical origin of their
phase diagrams. We suggest that, in addition to a thermodynamic mass
enhancement, these experiments may directly indicate the increasing role of
quantum fluctuations that suppress the oscillation amplitude through inelastic
scattering. We show that the traditional theoretical approaches beyond
Lifshitz-Kosevich to calculate the oscillation amplitude in correlated metals
result in a contradiction with the third law of thermodynamics and suggest a
way to rectify this problem.Comment: PRB Rapid commun. (2017
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