Quantum Transport and Integrability of the Anderson Model for a Quantum Dot with Multiple Leads

We show that an Anderson Hamiltonian describing a quantum dot connected to multiple leads is integrable. A general expression for the non-linear conductance is obtained by combining the Bethe ansatz exact solution with Landauer-B\"uttiker theory. In the Kondo regime, a closed form expression is given for the matrix conductance at zero temperature and when all the leads are close to the symmetric point. A bias-induced splitting of the Kondo resonance is possible for three or more leads. Specifically, for $N$ leads, with each at a different chemical potential, there can be $N-1$ Kondo peaks in the conductance.Comment: 5 pages, 2 figure

Minimum Distance and Parameter Ranges of Locally Recoverable Codes with Availability from Fiber Products of Curves

We construct families of locally recoverable codes with availability $t\geq 2$ using fiber products of curves, determine the exact minimum distance of many families, and prove a general theorem for minimum distance of such codes. The paper concludes with an exploration of parameters of codes from these families and the fiber product construction more generally. We show that fiber product codes can achieve arbitrarily large rate and arbitrarily small relative defect, and compare to known bounds and important constructions from the literature

Nonspatial sequence coding in CA1 neurons

The hippocampus is critical to the memory for sequences of events, a defining feature of episodic memory. However, the fundamental neuronal mechanisms underlying this capacity remain elusive. While considerable research indicates hippocampal neurons can represent sequences of locations, direct evidence of coding for the memory of sequential relationships among nonspatial events remains lacking. To address this important issue, we recorded neural activity in CA1 as rats performed a hippocampus-dependent sequencememory task. Briefly, the task involves the presentation of repeated sequences of odors at a single port and requires rats to identify each item as “in sequence” or “out of sequence”. We report that, while the animals’ location and behavior remained constant, hippocampal activity differed depending on the temporal context of items—in this case, whether they were presented in or out of sequence. Some neurons showed this effect across items or sequence positions (general sequence cells), while others exhibited selectivity for specific conjunctions of item and sequence position information (conjunctive sequence cells) or for specific probe types (probe-specific sequence cells). We also found that the temporal context of individual trials could be accurately decoded from the activity of neuronal ensembles, that sequence coding at the single-cell and ensemble level was linked to sequence memory performance, and that slow-gamma oscillations (20–40 Hz) were more strongly modulated by temporal context and performance than theta oscillations (4–12 Hz). These findings provide compelling evidence that sequence coding extends beyond the domain of spatial trajectories and is thus a fundamental function of the hippocampus

Quantum Entanglement in the Two Impurity Kondo Model

In order to quantify quantum entanglement in two impurity Kondo systems, we calculate the concurrence, negativity, and von Neumann entropy. The entanglement of the two Kondo impurities is shown to be determined by two competing many-body effects, the Kondo effect and the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, $I$. Due to the spin-rotational invariance of the ground state, the concurrence and negativity are uniquely determined by the spin-spin correlation between the impurities. It is found that there exists a critical minimum value of the antiferromagnetic correlation between the impurity spins which is necessary for entanglement of the two impurity spins. The critical value is discussed in relation with the unstable fixed point in the two impurity Kondo problem. Specifically, at the fixed point there is no entanglement between the impurity spins. Entanglement will only be created (and quantum information processing (QIP) be possible) if the RKKY interaction exchange energy, $I$, is at least several times larger than the Kondo temperature, $T_K$. Quantitative criteria for QIP are given in terms of the impurity spin-spin correlation.Comment: 7 pages, 3 figures, 1 tabl

Enhancing Childrens Social-Emotional Learning Skills Through Mindfulness Practices

Background: The Kalamazoo Eastside neighborhood has been subject to a great deal of economic and functional instability, particularly impacting the youth. Local demographic studies indicate that 90% of children are eligible for free or reduced lunch due to low income, 58% of households are single-female households, and 29% of parents do not have a high school diploma. Eastside Youth Strong (EYS) is a local organization focused on improving the lives of these children. This study will be investigating the EYS afterschool program’s mindfulness initiative. Purpose: Social and emotional learning were chosen to be studied because these skills are critical for children’s success in academic environments and personal lives. We hypothesize that implementing mindfulness practices at EYS will improve social and emotional learning outcomes because feasible outcomes were reported at other afterschool programs with similar interventions.1,2,3 Materials and Methods: This retrospective study explores the benefits of mindfulness techniques conducted on EYS children as measured through the Devereux Student Strengths Assessment (DESSA). The DESSA is a standardized measurement of competencies and social-emotional needs of each participating child compared to similarly aged children nationally. EYS staff were trained by a mindfulness expert on how to administer 10-minute mindful immersion, breathing exercises, body scanning, and meditation sessions Monday-Wednesday during the afterschool program. The DESSA is administered at the beginning (September), middle (March), and end (May) of the school year. We will analyze the data with the help of the WMed Biostatistics team. Results: In the first DESSA administration, 20 children were evaluated, and their ratings of the social-emotional composite were 0 Strength (0%), 7 Typical (35%), and 13 Need (65%). Conclusion: The results and data for this project are still in progress, but the upcoming DESSA results from March and May of the 2016-2017 school year will be analyzed and compared to the initial data. Furthermore, students’ progress over the year can be compared to students from past years. From the initial data and anecdotal observations of the EYC staff, there has been improvement in students’ overall attention span and patience in the afterschool program after the implementation of mindfulness; however, statistical improvement will be determined when all DESSA surveys have been completed

Piloting the Digital Experience Insights Service (November 2018): The University of Queensland

In 2018 a\ua0partnership between staff in the Institute for Teaching and Learning Innovation (ITaLI) and the UQ Library facilitated an institutional survey to investigate students' digital experiences and perspectives whilst studying at the University.\ua0The team engaged with other universities globally to pilot the survey instrument 'Digital experience insights survey' developed by JISC in the UK. Nearly 10,000 UQ students responded.\ua0This survey was very timely in allowing the University to understand the digital affordances and needs of the students and build these into upcoming digital initiatives. The case study url is\ua0https://digitalinsights.jisc.ac.uk/case-study-listing/university-queensland

Thermal and electrical currents in nanoscale electronic interferometers

We theoretically study thermal transport in an electronic interferometer comprising a parallel circuit of two quantum dots, each of which has a tunable single electronic state which are connected to two leads at different temperature. As a result of quantum interference, the heat current through one of the dots is in the opposite direction to the temperature gradient. An excess heat current flows through the other dot. Although locally, heat flows from cold to hot, globally the second law of thermodynamics is not violated because the entropy current associated with heat transfer through the whole device is still positive. The temperature gradient also induces a circulating electrical current, which makes the interferometer magnetically polarized

Exploring extensions to the standard cosmological model and the impact of baryons on small scales

It has been claimed that the standard model of cosmology (ΛCDM) cannot easily account for a number of observations on relatively small scales, motivating extensions to the standard model. Here, we introduce a new suite of cosmological simulations that systematically explores three plausible extensions: warm dark matter, self-interacting dark matter, and a running of the scalar spectral index of density fluctuations. Current observational constraints are used to specify the additional parameters that come with these extensions. We examine a large range of observable metrics on small scales, including the halo mass function, density, and circular velocity profiles, the abundance of satellite subhaloes, and halo concentrations. For any given metric, significant degeneracies can be present between the extensions. In detail, however, the different extensions have quantitatively distinct mass and radial dependencies, suggesting that a multiprobe approach over a range of scales can be used to break the degeneracies. We also demonstrate that the relative effects on the radial density profiles in the different extensions (compared to the standard model) are converged down to significantly smaller radii than are the absolute profiles. We compare the derived cosmological trends with the impact of baryonic physics using the EAGLE and ARTEMIS simulations. Significant degeneracies are also present between baryonic physics and cosmological variations (with both having similar magnitude effects on some observables). Given the inherent uncertainties both in the modelling of galaxy formation physics and extensions to ΛCDM, a systematic and simultaneous exploration of both is strongly warranted