5,013 research outputs found
Wave scattering and splitting by magnetic metamaterials
We study experimentally propagation of electromagnetic waves
through a slab of uniaxial magnetic metamaterial. We observe a range of
novel phenomena including partial focusing and splitting into multiple
transmitted beams.We demonstrate that while some of these experimentally
observed effects can be described within the approximation of an effective
medium, a deeper understanding of the experimental results requires a
rigorous study of internal eigenmodes of the lattice of resonators
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Tera-Hertz Coherent Radiation from Steady-State Microbunching in Storage Rings with X-band Radio-Frequency System
A Crucial Test for Color-Octet Production Mechanism in Z^0 Decays
The direct production rates of -wave charmonia in the decays of is
evaluated. The color-octet production processes are shown to have distinctively large branching ratios, the same order
of magnitude as that of prodution, as compared with other -wave
charmonium production mechanisms. This may suggest a crucial channel to test
the color-octet mechanism as well as to observe the -wave charmonium states
in decays. In addition, a signal for the charmonium as strong as
or with large transverse momentum at the Tevatron should
also be observed.Comment: 14 pages in LaTex (3 figures in PS-file
Review of HBT or Bose-Einstein correlations in high energy heavy ion collisions
A brief review is given on the discovery and the first five decades of the
Hanbury Brown - Twiss effect and its generalized applications in high energy
nuclear and particle physics, that includes a meta-review. Interesting and
inspiring new directions are also highlighted, including for example source
imaging, lepton and photon interferometry, non-Gaussian shape analysis as well
as many other new directions. Existing models are compared to two-particle
correlation measurements and the so-called RHIC HBT puzzle is resolved.
Evidence for a (directional) Hubble flow is presented and the conclusion is
confirmed by a successful description of the pseudorapidity dependence of the
elliptic flow as measured in Au+Au collisions by the PHOBOS Collaboration.Comment: 14 pages, 1 figure, 8 sub-figures, invited plenary talk at the
ICPA-QGP 2005 conference in Kolkata, Indi
A Survey of Air-to-Ground Propagation Channel Modeling for Unmanned Aerial Vehicles
In recent years, there has been a dramatic increase in the use of unmanned
aerial vehicles (UAVs), particularly for small UAVs, due to their affordable
prices, ease of availability, and ease of operability. Existing and future
applications of UAVs include remote surveillance and monitoring, relief
operations, package delivery, and communication backhaul infrastructure.
Additionally, UAVs are envisioned as an important component of 5G wireless
technology and beyond. The unique application scenarios for UAVs necessitate
accurate air-to-ground (AG) propagation channel models for designing and
evaluating UAV communication links for control/non-payload as well as payload
data transmissions. These AG propagation models have not been investigated in
detail when compared to terrestrial propagation models. In this paper, a
comprehensive survey is provided on available AG channel measurement campaigns,
large and small scale fading channel models, their limitations, and future
research directions for UAV communication scenarios
CMB-S4 Science Book, First Edition
This book lays out the scientific goals to be addressed by the
next-generation ground-based cosmic microwave background experiment, CMB-S4,
envisioned to consist of dedicated telescopes at the South Pole, the high
Chilean Atacama plateau and possibly a northern hemisphere site, all equipped
with new superconducting cameras. CMB-S4 will dramatically advance cosmological
studies by crossing critical thresholds in the search for the B-mode
polarization signature of primordial gravitational waves, in the determination
of the number and masses of the neutrinos, in the search for evidence of new
light relics, in constraining the nature of dark energy, and in testing general
relativity on large scales
Statistical mechanics of the vertex-cover problem
We review recent progress in the study of the vertex-cover problem (VC). VC
belongs to the class of NP-complete graph theoretical problems, which plays a
central role in theoretical computer science. On ensembles of random graphs, VC
exhibits an coverable-uncoverable phase transition. Very close to this
transition, depending on the solution algorithm, easy-hard transitions in the
typical running time of the algorithms occur.
We explain a statistical mechanics approach, which works by mapping VC to a
hard-core lattice gas, and then applying techniques like the replica trick or
the cavity approach. Using these methods, the phase diagram of VC could be
obtained exactly for connectivities , where VC is replica symmetric.
Recently, this result could be confirmed using traditional mathematical
techniques. For , the solution of VC exhibits full replica symmetry
breaking.
The statistical mechanics approach can also be used to study analytically the
typical running time of simple complete and incomplete algorithms for VC.
Finally, we describe recent results for VC when studied on other ensembles of
finite- and infinite-dimensional graphs.Comment: review article, 26 pages, 9 figures, to appear in J. Phys. A: Math.
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Hyperfine Spectroscopy of Isotopically Engineered Group-IV Color Centers in Diamond
A quantum register coupled to a spin-photon interface is a key component in
quantum communication and information processing. Group-IV color centers in
diamond (SiV, GeV, and SnV) are promising candidates for this application,
comprising an electronic spin with optical transitions coupled to a nuclear
spin as the quantum register. However, the creation of a quantum register for
these color centers with deterministic and strong coupling to the spin-photon
interface remains challenging. Here, we make first-principles predictions of
the hyperfine parameters of the group-IV color centers, which we verify
experimentally with a comprehensive comparison between the spectra of spin
active and spin neutral intrinsic dopant nuclei in single GeV and SnV emitters.
In line with the theoretical predictions, detailed spectroscopy on large sample
sizes reveals that hyperfine coupling causes a splitting of the optical
transition of SnV an order of magnitude larger than the optical linewidth and
provides a magnetic-field insensitive transition. This strong coupling provides
access to a new regime for quantum registers in diamond color centers, opening
avenues for novel spin-photon entanglement and quantum sensing schemes for
these well-studied emitters
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