101 research outputs found
Atomic collapse, Lorentz boosts, Klein scattering, and other quantum-relativistic phenomena in graphene
Electrons in graphene, behaving as massless relativistic Dirac particles,
provide a new perspective on the relation between condensed matter and
high-energy physics. We discuss atomic collapse, a novel state of superheavy
atoms stripped of their discrete energy levels, which are transformed into
resonant states. Charge impurities in graphene provide a convenient condensed
matter system in which this effect can be explored. Relativistic dynamics also
manifests itself in another system, graphene p-n junctions. We show how the
transport problem in the presence of magnetic field can be solved with the help
of a Lorentz transformation, and use it to investigate magnetotransport in p-n
junctions. Finally, we review recent proposal to use Fabry-Perot resonances in
p-n-p structures as a vehicle to investigate Klein scattering, another hallmark
phenomenon of relativistic dynamics.Comment: minireview, 9 pg
SRGeJ045359.9+622444: A 55-min Period Eclipsing AM CVn Discovered from a Joint SRG/eROSITA + ZTF Search
AM CVn systems are ultra-compact binaries where a white dwarf accretes from a
helium-rich degenerate or semi-degenerate donor. Some AM CVn systems will be
among the loudest sources of gravitational waves for the upcoming Laser
Interferometer Space Antenna (LISA), yet the formation channel of AM CVns
remains uncertain. We report the study and characterisation of a new eclipsing
AM CVn, SRGeJ045359.9+622444 (hereafter SRGeJ0453), discovered from a joint
SRG/eROSITA and ZTF program to identify cataclysmic variables (CVs). We
obtained optical photometry to confirm the eclipse of SRGeJ0453 and determine
the orbital period to be min. We
constrain the binary parameters by modeling the high-speed photometry and
radial velocity curves and find
and . The X-ray spectrum is
approximated by a power-law model with an unusually flat photon index of
previously seen in magnetic CVs with SRG/eROSITA, but verifying
the magnetic nature of SRGeJ0453 requires further investigation. Optical
spectroscopy suggests that the donor star of SRGeJ0453 could have initially
been a He star or a He white dwarf. SRGeJ0453 is the ninth eclipsing AM CVn
system published to date, and its lack of optical outbursts have made it
elusive in previous surveys. The discovery of SRGeJ0453 using joint X-ray and
optical surveys highlights the potential for discovering similar systems in the
near future.Comment: Submitted to Ap
PERESTROIKA, PEMIKIRAN BARU UNTUK KAMI DAN DUNIA
xii; 199 hlm;15,5 x 24 c
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