3,810 research outputs found
Do We Really Know that Oil Caused the Great Stagflation? A Monetary Alternative
This paper argues that major oil price increases were not nearly as essential a part of the causal mechanism that generated the stagflation of the 1970s as is often thought. There is neither a theoretical presumption that oil supply shocks are stagflationary nor robust empirical evidence for this view. In contrast, we show that monetary expansions and contractions can generate stagflation of realistic magnitude even in the absence of supply shocks. Furthermore, monetary fluctuations help to explain the historical movements of the prices of oil and other commodities, including the surge in the prices of industrial commodities that preceded the 1973/74 oil price increase. Thus, they can account for the striking coincidence of major oil price increases and worsening stagflation.
Catastrophic forgetting: still a problem for DNNs
We investigate the performance of DNNs when trained on class-incremental
visual problems consisting of initial training, followed by retraining with
added visual classes. Catastrophic forgetting (CF) behavior is measured using a
new evaluation procedure that aims at an application-oriented view of
incremental learning. In particular, it imposes that model selection must be
performed on the initial dataset alone, as well as demanding that retraining
control be performed only using the retraining dataset, as initial dataset is
usually too large to be kept. Experiments are conducted on class-incremental
problems derived from MNIST, using a variety of different DNN models, some of
them recently proposed to avoid catastrophic forgetting. When comparing our new
evaluation procedure to previous approaches for assessing CF, we find their
findings are completely negated, and that none of the tested methods can avoid
CF in all experiments. This stresses the importance of a realistic empirical
measurement procedure for catastrophic forgetting, and the need for further
research in incremental learning for DNNs.Comment: 10 pages, 11 figures, Artificial Neural Networks and Machine Learning
- ICANN 201
Automated NLO QCD Corrections with WHIZARD
We briefly discuss the current status of NLO QCD automation in the Monte
Carlo event generator WHIZARD. The functionality is presented for the explicit
study of off-shell top quark production with associated backgrounds at a lepton
collider.Comment: 9 pages, 5 figures, to appear in the proceedings of the European
Physical Society Conference on High Energy Physics 2015 (EPS-HEP 2015),
Vienna, Austria, 22nd to 29th of July 201
Matching NLO QCD Corrections in WHIZARD with the POWHEG scheme
Building on the new automatic subtraction of NLO amplitudes in WHIZARD, we
present our implementation of the POWHEG scheme to match radiative corrections
consistently with the parton shower. We apply this general framework to two
linear collider processes, and
.Comment: 7 pages, 4 figures, to appear in the proceedings of the European
Physical Society Conference on High Energy Physics 2015 (EPS-HEP 2015),
Vienna, Austria, 22nd to 29th of July 201
QCD NLO with Powheg matching and top threshold matching in WHIZARD
We present the status of the automation of NLO processes within the event
generator WHIZARD. The program provides an automated FKS subtraction and phase
space integration over the FKS regions, while the (QCD) NLO matrix element is
accessed via the Binoth Les Houches Interface from an externally linked
one-loop program. Massless and massive test cases and validation are shown for
several e+e- processes. Furthermore, we discuss work in progress and future
plans. The second part covers the matching of the NRQCD prediction with NLL
threshold resummation to the NLO continuum top pair production at lepton
colliders. Both the S-wave and P-wave production of the top pair are taken into
account in the resummation. The inclusion in WHIZARD allows to study more
exclusive observables than just the total cross section and automatically
accounts for important electroweak and relativistic corrections in the
threshold region.Comment: 9 pages, 3 figures, Talk given at 12th International Symposium on
Radiative Corrections (Radcor 2015) and LoopFest XIV (Radiative Corrections
for the LHC and Future Colliders); v2: reference adde
Automation of NLO processes and decays and POWHEG matching in WHIZARD
We give a status report on the automation of next-to-leading order processes
within the Monte Carlo event generator WHIZARD, using GoSam and OpenLoops as
provider for one-loop matrix elements. To deal with divergences, WHIZARD uses
automated FKS subtraction, and the phase space for singular regions is
generated automatically. NLO examples for both scattering and decay processes
with a focus on e+e- processes are shown. Also, first NLO-studies of
observables for collisions of polarized leptons beams, e.g. at the ILC, will be
presented. Furthermore, the automatic matching of the fixed-order NLO
amplitudes with emissions from the parton shower within the POWHEG formalism
inside WHIZARD will be discussed. We also present results for top pairs at
threshold in lepton collisions, including matching between a resummed threshold
calculation and fixed-order NLO. This allows the investigation of more
exclusive differential observables.Comment: 5 pages, 3 figures, Talk presented at ACAT 2016 at UTFSM,
Valpara\'iso, Chil
Modern Particle Physics Event Generation with WHIZARD
We describe the multi-purpose Monte-Carlo event generator WHIZARD for the
simulation of high-energy particle physics experiments. Besides the
presentation of the general features of the program like SM physics, BSM
physics, and QCD effects, special emphasis will be given to the support of the
most accurate simulation of the collider environments at hadron colliders and
especially at future linear lepton colliders. On the more technical side, the
very recent code refactoring towards a completely object-oriented software
package to improve maintainability, flexibility and code development will be
discussed. Finally, we present ongoing work and future plans regarding
higher-order corrections, more general model support including the setup to
search for new physics in vector boson scattering at the LHC, as well as
several lines of performance improvements.Comment: 7 pages; contribution to the proceedings of the conference "ACAT 2014
(Advanced Computing and Analysis Techniques in physics)", Prague, Czech
Republic, September 201
Top Physics in WHIZARD
In this talk we summarize the top physics setup in the event generator
WHIZARD with a main focus on lepton colliders. This includes full six-, eight-
and ten-fermion processes, factorized processes and spin correlations. For
lepton colliders, QCD NLO processes for top quark physics are available and
will be discussed. A special focus is on the top-quark pair threshold, where a
special implementation combines a non-relativistic effective field theory
calculation augmented by a next-to-leading threshold logarithm resummation with
a continuum relativistic fixed-order QCD NLO simulation.Comment: 6 pages, 2 figures, Talk presented at the International Workshop on
Future Linear Colliders (LCWS15), Whistler, Canada, 2-6 November 201
Order from disorder: Quantum spin gap in magnon spectra of LaTiO_3
A theory of the anisotropic superexchange and low energy spin excitations in
a Mott insulator with t_{2g} orbital degeneracy is presented. We observe that
the spin-orbit coupling induces frustrating Ising-like anisotropy terms in the
spin Hamiltonian, which invalidate noninteracting spin wave theory. The
frustration of classical states is resolved by an order from disorder
mechanism, which selects a particular direction of the staggered moment and
generates a quantum spin gap. The theory explains well the observed magnon gaps
in LaTiO_3. As a test case, a specific prediction is made on the splitting of
magnon branches at certain momentum directions.Comment: 5 pages, 2 figures, final versio
Maximum rates of climate change are systematically underestimated in the geological record
D.B.K. was supported by NERC Fellowship grant NE/I02089X/1 and W.K. by DFG grant Ki 806/12-1. Jonny Beedell is thanked for his help in data compilation and Michael Joachimski for discussions.Peer reviewedPublisher PD
- …