836 research outputs found
Advanced Technologies in Energy-Economy Models for Climate Change Assessment
Considerations regarding the roles of advanced technologies are crucial in energy-economic modeling, as these technologies, while usually not yet commercially viable, could substitute for fossil energy when relevant policies are in place. To improve the representation of the penetration of advanced technologies, we present a formulation that is parameterized based on observations, while capturing elements of rent and real cost increases if high demand suddenly appears due to large policy shock. The formulation is applied to a global economy-wide model to study the roles of low carbon alternatives in the power sector. While other modeling approaches often adopt specific constraints on expansion, our approach is based on the assumption and observation that these constraints are not absolute—the rate at which advanced technologies will expand is endogenous to economic incentives. The policy simulations are designed to illustrate the response under sudden increased demand for the advanced technologies, and are not intended to represent necessarily realistic price paths for greenhouse gas emissions.The authors gratefully acknowledge the financial support for this work provided by the MIT Joint Program on the Science and Policy of Global Change through a consortium of industrial sponsors and Federal grants. Suggestions and feedback from participants of the MIT EPPA meeting and Jamie Bartholomay are highly appreciated
The MIT EPPA6 Model: Economic Growth, Energy Use, and Food Consumption
The MIT Economic Projection and Policy Analysis (EPPA) model has been broadly applied on energy and climate policy analyses. In this paper, we provide an updated version of the model based on the most recent global economic database with the base year data of 2007. Also new in this version of the model are non-homothetic preferences, a revised capital vintaging structure, separate accounting of residences, and an improved model structure that smooths its functioning and makes future extensions easier. We compare reference (“business-as-usual”) and policy results for the latest model to the previous version. We also present how projections for the final consumption of food and agricultural products are improved with non-homothetic preferences, and how various assumptions for reference GDP growth, elasticity of substitution between energy and non-energy input, and autonomous energy efficiency improvement may change CO2 emissions and prices.We gratefully acknowledge the financial support for this work provided by the MIT Joint Program on the Science and Policy of Global Change through a consortium of industrial sponsors and Federal grants
Prevalent Behavior of Strongly Order Preserving Semiflows
Classical results in the theory of monotone semiflows give sufficient
conditions for the generic solution to converge toward an equilibrium or
towards the set of equilibria (quasiconvergence). In this paper, we provide new
formulations of these results in terms of the measure-theoretic notion of
prevalence. For monotone reaction-diffusion systems with Neumann boundary
conditions on convex domains, we show that the set of continuous initial data
corresponding to solutions that converge to a spatially homogeneous equilibrium
is prevalent. We also extend a previous generic convergence result to allow its
use on Sobolev spaces. Careful attention is given to the measurability of the
various sets involved.Comment: 18 page
On Traversable Lorentzian Wormholes in the Vacuum Low Energy Effective String Theory in Einstein and Jordan Frames
Three new classes (II-IV) of solutions of the vacuum low energy effective
string theory in four dimensions are derived. Wormhole solutions are
investigated in those solutions including the class I case both in the Einstein
and in the Jordan (string) frame. It turns out that, of the eight classes of
solutions investigated (four in the Einstein frame and four in the
corresponding string frame), massive Lorentzian traversable wormholes exist in
five classes. Nontrivial massless limit exists only in class I Einstein frame
solution while none at all exists in the string frame. An investigation of test
scalar charge motion in the class I solution in the two frames is carried out
by using the Plebanski-Sawicki theorem. A curious consequence is that the
motion around the extremal zero (Keplerian) mass configuration leads, as a
result of scalar-scalar interaction, to a new hypothetical "mass" that confines
test scalar charges in bound orbits, but does not interact with neutral test
particles.Comment: 18 page
Scalar Levin-Type Sequence Transformations
Sequence transformations are important tools for the convergence acceleration
of slowly convergent scalar sequences or series and for the summation of
divergent series. Transformations that depend not only on the sequence elements
or partial sums but also on an auxiliary sequence of so-called remainder
estimates are of Levin-type if they are linear in the , and
nonlinear in the . Known Levin-type sequence transformations are
reviewed and put into a common theoretical framework. It is discussed how such
transformations may be constructed by either a model sequence approach or by
iteration of simple transformations. As illustration, two new sequence
transformations are derived. Common properties and results on convergence
acceleration and stability are given. For important special cases, extensions
of the general results are presented. Also, guidelines for the application of
Levin-type sequence transformations are discussed, and a few numerical examples
are given.Comment: 59 pages, LaTeX, invited review for J. Comput. Applied Math.,
abstract shortene
Low Q^2 Jet Production at HERA and Virtual Photon Structure
The transition between photoproduction and deep-inelastic scattering is
investigated in jet production at the HERA ep collider, using data collected by
the H1 experiment. Measurements of the differential inclusive jet
cross-sections dsigep/dEt* and dsigmep/deta*, where Et* and eta* are the
transverse energy and the pseudorapidity of the jets in the virtual
photon-proton centre of mass frame, are presented for 0 < Q2 < 49 GeV2 and 0.3
< y < 0.6. The interpretation of the results in terms of the structure of the
virtual photon is discussed. The data are best described by QCD calculations
which include a partonic structure of the virtual photon that evolves with Q2.Comment: 20 pages, 5 Figure
Hadron Production in Diffractive Deep-Inelastic Scattering
Characteristics of hadron production in diffractive deep-inelastic
positron-proton scattering are studied using data collected in 1994 by the H1
experiment at HERA. The following distributions are measured in the
centre-of-mass frame of the photon dissociation system: the hadronic energy
flow, the Feynman-x (x_F) variable for charged particles, the squared
transverse momentum of charged particles (p_T^{*2}), and the mean p_T^{*2} as a
function of x_F. These distributions are compared with results in the gamma^* p
centre-of-mass frame from inclusive deep-inelastic scattering in the
fixed-target experiment EMC, and also with the predictions of several Monte
Carlo calculations. The data are consistent with a picture in which the
partonic structure of the diffractive exchange is dominated at low Q^2 by hard
gluons.Comment: 16 pages, 6 figures, submitted to Phys. Lett.
Energy Flow in the Hadronic Final State of Diffractive and Non-Diffractive Deep-Inelastic Scattering at HERA
An investigation of the hadronic final state in diffractive and
non--diffractive deep--inelastic electron--proton scattering at HERA is
presented, where diffractive data are selected experimentally by demanding a
large gap in pseudo --rapidity around the proton remnant direction. The
transverse energy flow in the hadronic final state is evaluated using a set of
estimators which quantify topological properties. Using available Monte Carlo
QCD calculations, it is demonstrated that the final state in diffractive DIS
exhibits the features expected if the interaction is interpreted as the
scattering of an electron off a current quark with associated effects of
perturbative QCD. A model in which deep--inelastic diffraction is taken to be
the exchange of a pomeron with partonic structure is found to reproduce the
measurements well. Models for deep--inelastic scattering, in which a
sizeable diffractive contribution is present because of non--perturbative
effects in the production of the hadronic final state, reproduce the general
tendencies of the data but in all give a worse description.Comment: 22 pages, latex, 6 Figures appended as uuencoded fil
A Search for Selectrons and Squarks at HERA
Data from electron-proton collisions at a center-of-mass energy of 300 GeV
are used for a search for selectrons and squarks within the framework of the
minimal supersymmetric model. The decays of selectrons and squarks into the
lightest supersymmetric particle lead to final states with an electron and
hadrons accompanied by large missing energy and transverse momentum. No signal
is found and new bounds on the existence of these particles are derived. At 95%
confidence level the excluded region extends to 65 GeV for selectron and squark
masses, and to 40 GeV for the mass of the lightest supersymmetric particle.Comment: 13 pages, latex, 6 Figure
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