Gravity and the Quantum: Are they Reconcilable?

General relativity and quantum mechanics are conflicting theories. The seeds of discord are the fundamental principles on which these theories are grounded. General relativity, on one hand, is based on the equivalence principle, whose strong version establishes the local equivalence between gravitation and inertia. Quantum mechanics, on the other hand, is fundamentally based on the uncertainty principle, which is essentially nonlocal in the sense that a particle does not follow one trajectory, but infinitely many trajectories, each one with a different probability. This difference precludes the existence of a quantum version of the strong equivalence principle, and consequently of a quantum version of general relativity. Furthermore, there are compelling experimental evidences that a quantum object in the presence of a gravitational field violates the weak equivalence principle. Now it so happens that, in addition to general relativity, gravitation has an alternative, though equivalent description, given by teleparallel gravity, a gauge theory for the translation group. In this theory torsion, instead of curvature, is assumed to represent the gravitational field. These two descriptions lead to the same classical results, but are conceptually different. In general relativity, curvature geometrizes the interaction, while torsion in teleparallel gravity acts as a force, similar to the Lorentz force of electrodynamics. Because of this peculiar property, teleparallel gravity describes the gravitational interaction without requiring any of the equivalence principles. The replacement of general relativity by teleparallel gravity may, in consequence, lead to a conceptual reconciliation of gravitation with quantum mechanics.Comment: 15 pages, 2 figures. Talk presented at the conference "Quantum Theory: Reconsideration of Foundations-3", June 6-11, 2005, Vaxjo University, Vaxjo, Swede

Gravitation without the equivalence principle

In the general relativistic description of gravitation, geometry replaces the concept of force. This is possible because of the universal character of free fall, and would break down in its absence. On the other hand, the teleparallel version of general relativity is a gauge theory for the translation group and, as such, describes the gravitational interaction by a force similar to the Lorentz force of electromagnetism, a non-universal interaction. Relying on this analogy it is shown that, although the geometric description of general relativity necessarily requires the existence of the equivalence principle, the teleparallel gauge approach remains a consistent theory for gravitation in its absence.Comment: Latex, 11 pages, no figures. Minor presentation changes. Version to appear in Gen. Rel. Grav. (2004

Doing without the Equivalence Principle

In Einstein's general relativity, geometry replaces the concept of force in the description of the gravitation interaction. Such an approach rests on the universality of free-fall--the weak equivalence principle--and would break down without it. On the other hand, the teleparallel version of general relativity, a gauge theory for the translation group, describes the gravitational interaction by a force similar to the Lorentz force of electromagnetism, a non-universal interaction. It is shown that, similarly to the Maxwell's description of electromagnetism, the teleparallel gauge approach provides a consistent theory for gravitation even in the absence of the weak equivalence principle.Comment: 7 pages, no figures. Talk presented at the "Tenth Marcel Grossmann Meeting", July 20 to 26, 2003, Rio de Janeiro, Brazil; to be published in the Proceedings (World Scientific, Singapore, 2005

Bringing Together Gravity and the Quanta

Due to its underlying gauge structure, teleparallel gravity achieves a separation between inertial and gravitational effects. It can, in consequence, describe the isolated gravitational interaction without resorting to the equivalence principle, and is able to provide a tensorial definition for the energy-momentum density of the gravitational field. Considering the conceptual conflict between the local equivalence principle and the nonlocal uncertainty principle, the replacement of general relativity by its teleparallel equivalent can be considered an important step towards a prospective reconciliation between gravitation and quantum mechanics.Comment: 9 pages. Contribution to the proceedings of the Albert Einstein Century International Conference, Paris, 18-22 July, 200

Kinetic-Ion Simulations Addressing Whether Ion Trapping Inflates Stimulated Brillouin Backscattering Reflectivities

An investigation of the possible inflation of stimulated Brillouin backscattering (SBS) due to ion kinetic effects is presented using electromagnetic particle simulations and integrations of three-wave coupled-mode equations with linear and nonlinear models of the nonlinear ion physics. Electrostatic simulations of linear ion Landau damping in an ion acoustic wave, nonlinear reduction of damping due to ion trapping, and nonlinear frequency shifts due to ion trapping establish a baseline for modeling the electromagnetic SBS simulations. Systematic scans of the laser intensity have been undertaken with both one-dimensional particle simulations and coupled-mode-equations integrations, and two values of the electron-to-ion temperature ratio (to vary the linear ion Landau damping) are considered. Three of the four intensity scans have evidence of SBS inflation as determined by observing more reflectivity in the particle simulations than in the corresponding three-wave mode-coupling integrations with a linear ion-wave model, and the particle simulations show evidence of ion trapping.Comment: 56 pages, 20 figure

Grassroots facilitators as agents of change for promoting sustainable forest management: lessons learned from REDD+ capacity development in Asia

This article aims to provide policymakers and other key stakeholders with insights into the issues and concerns of grassroots stakeholders with regards to REDD+2 policy and programme development. The lessons shared spring from experiences in REDD+ capacity development in South and South-East Asia, covering Indonesia, Lao People's Democratic Republic, Myanmar, Nepal and Viet Nam. Extensive participatory and contextualized discussions and a series of training events contributed to building a cadre of hundreds of REDD+ trainers and facilitators at different levels and reached out to thousands of grassroots communities in project countries.The opportunities and challenges involved in strengthening communication between policymakers and local stakeholders are highlighted

Performance Evaluation of Traveling Wave Fault Locator for a 220kV Hoa Khanh-Thanh My Transmission Line

This paper presents the traveling wave based fault location methods of SEL-400L, and SFL-2000 available on the market for a 66.9km, 220kV Hoa Khanh-Thanh My transmission line in Central Viet Nam, such as single-ended, and double-ended, all of which rely on measurements from inductive CTs and capacitive VTs. Focus was given on the building process of a Matlab Simulink model to evaluate these methods. Current and voltage signals were sent to an analog Chebyshev type II filter which passes higher frequency signals at 3kHz and rejects low frequencies signal at 50Hz. After that, these output signals are used in Clarke's transformation for getting 0 and α components. The detail coefficient of the selected components after DWT using Db4 wavelet at decomposition level 1 can be used to determine the fault types, the direction of fault and propose a crest-wave comparison solution to identify exactly the adjacent bus' reflected wave from the fault point's reflected wave for the fault location. Finally, the accuracy of fault location on the transmission line is reviewed by varying various parameters like fault type, fault location and fault resistance on a given power system model

Mental Health Services Provision in Primary Care and Emergency Department Settings: Analysis of Blended Fee-for-Service and Blended Capitation Models in Ontario, Canada.

Treating mental illnesses in primary care is increasingly emphasized to improve access to mental health services. Although family physicians (FPs) or general practitioners are in an ideal position to provide the bulk of mental health care, it is unclear how best to remunerate FPs for the adequate provision of mental health services. We examined the quantity of mental health services provided in Ontario\u27s blended fee-for-service and blended capitation models. We evaluated the impact of FPs switching from blended fee-for-service to blended capitation on the provision of mental health services in primary care and emergency department using longitudinal health administrative data from 2007 to 2016. We accounted for the differences between those who switched to blended capitation and non-switchers in the baseline using propensity score weighted fixed-effects regressions to compare remuneration models. We found that switching from blended fee-for-service to blended capitation was associated with a 14% decrease (95% CI 12-14%) in the number of mental health services and an 18% decrease (95% CI 15-20%) in the corresponding value of services. This result was driven by the decrease in services during regular-hours. During after-hours, the number of services increased by 20% (95% CI 10-32%) and the corresponding value increased by 35% (95% CI 17-54%). Switching was associated with a 4% (95% CI 1-8%) decrease in emergency department visits for mental health reasons. Blended capitation reduced provision of mental health services without increasing emergency department visits, suggesting potential efficiency gain in the blended capitation model in Ontario

Physician remuneration schemes, psychiatric hospitalizations and follow-up care: Evidence from blended fee-for-service and capitation models.

Psychiatric hospitalizations could be reduced if mental illnesses were detected and treated earlier in the primary care setting, leading to the World Health Organization recommendation that mental health services be integrated into primary care. The mental health services provided in primary care settings may vary based on how physicians are incentivized. Little is known about the link between physician remuneration and psychiatric hospitalizations. We contribute to this literature by studying the relationship between physician remuneration and psychiatric hospitalizations in Canada\u27s most populous province, Ontario. Specifically, we study family physicians (FPs) who switched from blended fee-for-service (FFS) to blended capitation remuneration model, relative to those who remained in the blended FFS model, on psychiatric hospitalizations. Outcomes included psychiatric hospitalizations by enrolled patients and the proportion of hospitalized patients who had a follow-up visit with the FP within 14 days of discharge. We used longitudinal health administrative data from a cohort of practicing physicians from 2006 through 2016. Because physicians practicing in these two models are likely to be different, we employed inverse probability weighting based on estimated propensity scores to ensure that switchers and non-switchers were comparable at the baseline. Using inverse probability weighted fixed-effects regressions controlling for relevant confounders, we found that switching from blended FFS to blended capitation was associated with a 6.2% decrease in the number of psychiatric hospitalizations and a 4.7% decrease in the number of patients with a psychiatric hospitalization. No significant effect of remuneration on follow-up visits within 14 days of discharge was observed. Our results suggest that the blended capitation model is associated with fewer psychiatric hospitalizations relative to blended FFS

Latitudinal Variation in Top-Down and Bottom-Up Control of a Salt Marsh Food Web

The shrub Iva frutescens, which occupies the terrestrial border of U.S. Atlantic Coast salt marshes, supports a food web that varies strongly across latitude. We tested whether latitudinal variation in plant quality (higher at high latitudes), consumption by omnivores (a crab, present only at low latitudes), consumption by mesopredators (ladybugs, present at all latitudes), or the life history stage of an herbivorous beetle could explain continental-scale field patterns of herbivore density. In a mesocosm experiment, crabs exerted strong top-down control on herbivorous beetles, ladybugs exerted strong top-down control on aphids, and both predators benefited plants through trophic cascades. Latitude of plant origin had no effect on consumers. Herbivorous beetle density was greater if mesocosms were stocked with beetle adults rather than larvae, and aphid densities were reduced in the “adult beetle” treatment. Treatment combinations representing high and low latitudes produced patterns of herbivore density similar to those in the field. We conclude that latitudinal variation in plant quality is less important than latitudinal variation in top consumers and competition in mediating food web structure. Climate may also play a strong role in structuring high-latitude salt marshes by limiting the number of herbivore generations per growing season and causing high overwintering mortality