61,393 research outputs found
GRBs and fundamental physics
Gamma-ray bursts (GRBs) are short and intense flashes at the cosmological
distances, which are the most luminous explosions in the Universe. The high
luminosities of GRBs make them detectable out to the edge of the visible
universe. So, they are unique tools to probe the properties of high-redshift
universe: including the cosmic expansion and dark energy, star formation rate,
the reionization epoch and the metal evolution of the Universe. First, they can
be used to constrain the history of cosmic acceleration and the evolution of
dark energy in a redshift range hardly achievable by other cosmological probes.
Second, long GRBs are believed to be formed by collapse of massive stars. So
they can be used to derive the high-redshift star formation rate, which can not
be probed by current observations. Moreover, the use of GRBs as cosmological
tools could unveil the reionization history and metal evolution of the
Universe, the intergalactic medium (IGM) properties and the nature of first
stars in the early universe. But beyond that, the GRB high-energy photons can
be applied to constrain Lorentz invariance violation (LIV) and to test
Einstein's Equivalence Principle (EEP). In this paper, we review the progress
on the GRB cosmology and fundamental physics probed by GRBs.Comment: 38 pages, 18 figures, Review based on ISSI workshop "Gamma-Ray
Bursts: a Tool to Explore the Young Universe" (2015, Beijing, China),
accepted for publication in Space Science Review
Small radii of neutron stars as an indication of novel in-medium effects
At present, neutron star radii from both observations and model predictions
remain very uncertain. Whereas different models can predict a wide range of
neutron star radii, it is not possible for most models to predict radii that
are smaller than about 10 km, thus if such small radii are established in the
future they will be very difficult to reconcile with model estimates. By
invoking a new term in the equation of state that enhances the energy density,
but leaves the pressure unchanged we simulate the current uncertainty in the
neutron star radii. This new term can be possibly due to the exchange of the
weakly interacting light U-boson with appropriate in-medium parameters, which
does not compromise the success of the conventional nuclear models. The
validity of this new scheme will be tested eventually by more precise
measurements of neutron star radii.Comment: EPJA (2015) in pres
Primary-Filling e/3 Quasiparticle Interferometer
We report experimental realization of a quasiparticle interferometer where
the entire system is in 1/3 primary fractional quantum Hall state. The
interferometer consists of chiral edge channels coupled by quantum-coherent
tunneling in two constrictions, thus enclosing an Aharonov-Bohm area. We
observe magnetic flux and charge periods h/e and e/3, equivalent to creation of
one quasielectron in the island. Quantum theory predicts a 3h/e flux period for
charge e/3, integer statistics particles. Accordingly, the observed periods
demonstrate the anyonic statistics of Laughlin quasiparticles
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