Echo of the Quantum Bounce

We identify a signature of quantum gravitational effects that survives from the early universe to the current era: Fluctuations of quantum fields as seen by comoving observers are significantly influenced by the history of the early universe. In particular we show how the existence (or not) of a quantum bounce leaves a trace in the background quantum noise that is not damped and would be non-negligible even nowadays. Furthermore, we estimate an upper bound for the typical energy and length scales where quantum effects are relevant. We discuss how this signature might be observed and therefore used to build falsifiability tests of quantum gravity theories.Comment: Revtex4.1. 2 Figures. V2: Content extended and edited to match published versio

The Quantum Echo of the Early Universe

We show that the fluctuations of quantum fields as seen by late comoving observers are significantly influenced by the history of the early Universe, and therefore they transmit information about the nature of spacetime in timescales when quantum gravitational effects were non-negligible. We discuss how this may be observable even nowadays, and thus used to build falsifiability tests of quantum gravity theories.Comment: 3 pages. 2 Figures. Proceedings Theory Canada 9. Published in Canadian Journal of Physics. (http://www.nrcresearchpress.com/doi/abs/10.1139/cjp-2014-0567

Violation of the strong Huygen's principle and timelike signals from the early Universe

We analyze the implications of the violations of the strong Huygens principle in the transmission of information from the early universe to the current era via massless fields. We show that much more information reaches us through timelike channels (not mediated by real photons) than it is carried by rays of light, which are usually regarded as the only carriers of information.Comment: 5 pages, 2 figures. RevTeX 4.1. V2: Updated to match published version. Previous title "A glimpse of the early universe without real light" modified to match Physical Review Letters published versio

Graph theory analysis of resting-state functional magnetic resonance imaging in essential tremor.

Essential tremor (ET) is a neurological disease with both motor and non-motor manifestations; however, little is known about its underlying brain basis. Furthermore, the overall organization of the brain network in ET remains largely unexplored. We investigated the topological properties of brain functional network, derived from resting-state functional MRI data, in 23 ET patients vs. 23 healthy controls. Graph theory analysis was used to assess the functional network organization. At the global level, the functional network of ET patients was characterized by lower small-world values than healthy controls - less clustered functionality of the brain. At the regional level, compared with the healthy controls, ET patients showed significantly higher values of global efficiency, cost and degree, and a shorter average path length in the left inferior frontal gyrus (pars opercularis), right inferior temporal gyrus (posterior division and temporo-occipital part), right inferior lateral occipital cortex, left paracingulate, bilateral precuneus bilaterally, left lingual gyrus, right hippocampus, left amygdala, nucleus accumbens bilaterally, and left middle temporal gyrus. In addition, ET patients showed significant higher local efficiency and clustering coefficient values in the frontal medial cortex bilaterally, subcallosal cortex, posterior cingulate, parahippocampal gyri bilaterally (posterior division), right lingual gyrus, right cerebellar flocculus, right postcentral gyrus, right inferior semilunar lobule of cerebellum and culmen of vermis. In conclusion, the efficiency of the overall brain functional network in ET is disrupted. Further, our results support the concept that ET is a disorder that disrupts widespread brain regions, including those outside of the brain regions responsible for tremor.pre-print1168 K

Entangling nuclear spins in distant quantum dots via an electron bus

We propose a protocol for the deterministic generation of entanglement between two ensembles of nuclear spins surrounding two distant quantum dots. The protocol relies on the injection of electrons with definite polarization, their sequential interaction with the nuclear ensembles of each quantum dot for a short time, and the coherent transfer of each electron from one quantum dot to the other. Computing the exact dynamics for small systems, and using an effective master equation and approximate nonlinear equations of motion for larger systems, we are able to confirm that our protocol indeed produces entanglement for both homogeneous and inhomogeneous systems. Last, we analyze the feasibility of our protocol in several current experimental platforms

Entangling nuclear spins in distant quantum dots via an electron bus

We propose a protocol for the deterministic generation of entanglement between two ensembles of nuclear spins surrounding two distant quantum dots. The protocol relies on the injection of electrons with definite polarization in each quantum dot and the coherent transfer of electrons from one quantum dot to the other. Computing the exact dynamics for small systems, and using an effective master equation and approximate non-linear equations of motion for larger systems, we are able to confirm that our protocol indeed produces entanglement for both homogeneous and inhomogeneous systems. Last, we analyze the feasibility of our protocol in several current experimental platforms

Loop Quantum Gravity and the The Planck Regime of Cosmology

The very early universe provides the best arena we currently have to test quantum gravity theories. The success of the inflationary paradigm in accounting for the observed inhomogeneities in the cosmic microwave background already illustrates this point to a certain extent because the paradigm is based on quantum field theory on the curved cosmological space-times. However, this analysis excludes the Planck era because the background space-time satisfies Einstein's equations all the way back to the big bang singularity. Using techniques from loop quantum gravity, the paradigm has now been extended to a self-consistent theory from the Planck regime to the onset of inflation, covering some 11 orders of magnitude in curvature. In addition, for a narrow window of initial conditions, there are departures from the standard paradigm, with novel effects, such as a modification of the consistency relation involving the scalar and tensor power spectra and a new source for non-Gaussianities. Thus, the genesis of the large scale structure of the universe can be traced back to quantum gravity fluctuations \emph{in the Planck regime}. This report provides a bird's eye view of these developments for the general relativity community.Comment: 23 pages, 4 figures. Plenary talk at the Conference: Relativity and Gravitation: 100 Years after Einstein in Prague. To appear in the Proceedings to be published by Edition Open Access. Summarizes results that appeared in journal articles [2-13

Transit times and mean ages for nonautonomous and autonomous compartmental systems

We develop a theory for transit times and mean ages for nonautonomous compartmental systems. Using the McKendrick-von F\"orster equation, we show that the mean ages of mass in a compartmental system satisfy a linear nonautonomous ordinary differential equation that is exponentially stable. We then define a nonautonomous version of transit time as the mean age of mass leaving the compartmental system at a particular time and show that our nonautonomous theory generalises the autonomous case. We apply these results to study a nine-dimensional nonautonomous compartmental system modeling the terrestrial carbon cycle, which is a modification of the Carnegie-Ames-Stanford approach (CASA) model, and we demonstrate that the nonautonomous versions of transit time and mean age differ significantly from the autonomous quantities when calculated for that model

Chondrule sizes within the CM carbonaceous chondrites and measurement methodologies

The sizes of chondrules are a valuable tool for understanding relationships between meteorite groups and the affinity of ungrouped chondrites, documenting temporal/spatial variability in the solar nebula, and exploring the effects of parent body processing. Many of the recently reported sizes of chondrules within the CM carbonaceous chondrites differ significantly from the established literature average and are more closely comparable to those of chondrules within CO chondrites. Here, we report an updated analysis of chondrule dimensions within the CM group based on data from 1937 chondrules, obtained across a suite of CM lithologies ranging from petrologic subtypes CM2.2 to CM2.7. Our revised average CM chondrule size is 194 μm. Among the samples examined, a relationship was observed between petrologic subtype and chondrule size such that chondrule long‐axis lengths are greater in the more highly aqueously altered lithologies. These findings suggest a greater similarity between the CM and CO chondrites than previously thought and support arguments for a genetic link between the two groups (i.e., the CM‐CO clan). Using the 2‐D and 3‐D data gathered, we also apply numerous stereological corrections to examine their usefulness in correcting 2‐D chondrule measurements within the CM chondrites. Alongside this analysis, we present the details of a standardized methodology for 2‐D chondrule size measurement to facilitate more reliable inter‐study comparisons