136,058 research outputs found
On the origin of the hard X-Ray excess of high-synchrotron-peaked BL Lac object Mrk 421
For the first time, Kataoka \& Stawarz reported a clear detection of a hard
X-ray excess, above 20 keV, in the high-synchrotron-peaked BL Lac
object Mrk 421. We find that this feature may not be produced by the low-energy
part of the same electron population that produced the Fermi/LAT -ray.
Because of that it is required that the power-law electron energy go down to
, which predicts a very strong radio emission (radio
flux larger than the observed) even considering the synchrotron self-absorption
effect. We investigate the possibility of this excess being produced from the
spine/layer jet structure, which has been clearly detected in Mrk 421. We find
that (1) similar to one-zone modeling, the spine emissions provide good
modeling of the broadband spectral energy distribution, except for the hard
X-ray excess; and (2) the hard X-ray excess can be well represented by the
synchrotron photons (from the layer) being inverse Compton scattered by the
spine electrons.Comment: 20 pages, 3 figures, published versio
Exploring the framework of assemblage moment matrices and its applications in device-independent characterizations
In a recent work [Phys. Rev. Lett. 116, 240401 (2016)], a framework known by
the name of "assemblage moment matrices" (AMMs) has been introduced for the
device-independent quantification of quantum steerability and measurement
incompatibility. In other words, even with no assumption made on the
preparation device nor the measurement devices, one can make use of this
framework to certify, directly from the observed data, the aforementioned
quantum features. Here, we further explore the framework of AMM and provide
improved device-independent bounds on the generalized robustness of
entanglement, the incompatibility robustness and the incompatibility weight. We
compare the tightness of our device-independent bounds against those obtained
from other approaches. Along the way, we also provide an analytic form for the
generalized robustness of entanglement for an arbitrary two-qudit isotropic
state. When considering a Bell-type experiment in a tri- or more-partite
scenario, we further show that the framework of AMM provides a natural way to
characterize a superset to the set of quantum correlations, namely, one which
also allows post-quantum steering.Comment: 17 pages, 6 figures. Comments welcome
Natural Framework for Device-Independent Quantification of Quantum Steerability, Measurement Incompatibility, and Self-Testing
We introduce the concept of assemblage moment matrices, i.e., a collection of
matrices of expectation values, each associated with a conditional quantum
state obtained in a steering experiment. We demonstrate how it can be used for
quantum states and measurements characterization in a device-independent
manner, i.e., without invoking any assumption about the measurement or the
preparation device. Specifically, we show how the method can be used to lower
bound the steerability of an underlying quantum state directly from the
observed correlation between measurement outcomes. Combining such
device-independent quantifications with earlier results established by Piani
and Watrous [Phys. Rev. Lett. 114, 060404 (2015)], our approach immediately
provides a device-independent lower bound on the generalized robustness of
entanglement, as well as the usefulness of the underlying quantum state for a
type of subchannel discrimination problem. In addition, by proving a
quantitative relationship between steering robustness and the recently
introduced incompatibility robustness, our approach also allows for a
device-independent quantification of the incompatibility between various
measurements performed in a Bell-type experiment. Explicit examples where such
bounds provide a kind of self-testing of the performed measurements are
provided.Comment: The core of these results were already presented at the Workshop on
Quantum Nonlocality, Causal Structure and Device-independent Quantum
Information on 14/12/2016; v2: closely approximates journal version; v3:
title is updated as journal versio
Cultivating Contemplative Mind in the Classroom
In Fall 2019, we showed video interviews of successful (i.e., graduated) alumni to first-year seminar students in the hope that incoming students would be inspired to adopt similar success strategies leading to increased retention and completion of their UNLV degree. The Academic Success Center filmed interviews with ten UNLV graduates who took our first-year seminar, COLA 100E. These COLA 100E Success Stories were then edited into three videos, each focusing on a particular theme, such as the first-year transition, the major selection process, and the key tips for graduation. The goal was that these successfully-graduated students would serve as motivational role models for UNLV’s diverse first-year student population. Though the alumni echoed concepts taught in the class, we imagined these peers would be more relatable than the instructor alone, encouraging students to identify with and potentially adopt new approaches to and perspectives of success early in their college careers.https://digitalscholarship.unlv.edu/btp_expo/1090/thumbnail.jp
New classes of topological crystalline insulators with unpinned surface Dirac cones
We theoretically predict two new classes of three-dimensional topological
crystalline insulators (TCIs), which have an odd number of unpinned surface
Dirac cones protected by crystal symmetries. The first class is protected by a
single glide plane symmetry; the second class is protected by a composition of
a twofold rotation and time-reversal symmetry. Both classes of TCIs are
characterized by a quantized Berry phase associated with surface states
and a topological invariant associated with the bulk bands. In the
presence of disorder, these TCI surface states are protected against
localization by the average crystal symmetries, and exhibit critical
conductivity in the universality class of the quantum Hall plateau transition.
These new TCIs exist in time-reversal-breaking systems with or without
spin-orbital coupling, and their material realizations are discussed.Comment: 4 pages plus supplementary material
- …