590 research outputs found
Thermoelectric DC conductivities with momentum dissipation from higher derivative gravity
We present a mechanism of momentum relaxation in higher derivative gravity by
adding linear scalar fields to the Gauss-Bonnet theory. We analytically
computed all of the DC thermoelectric conductivities in this theory by adopting
the method given by Donos and Gauntlett in [arXiv:1406.4742]. The results show
that the DC electric conductivity is not a monotonic function of the effective
impurity parameter : in the small limit, the DC conductivity is
dominated by the coherent phase, while for larger , pair creation
contribution to the conductivity becomes dominant, signaling an incoherent
phase. In addition, the DC heat conductivity is found independent of the
Gauss-Bonnet coupling constant.Comment: 1+19 pages, 2 figures,typos in Eq.(40) correcte
Astrocytic expression of Parkinson's disease-related A53T α-synuclein causes neurodegeneration in mice
<p>Abstract</p> <p>Background</p> <p>Parkinson's disease (PD) is the most common movement disorder. While neuronal deposition of α-synuclein serves as a pathological hallmark of PD and Dementia with Lewy Bodies, α-synuclein-positive protein aggregates are also present in astrocytes. The pathological consequence of astrocytic accumulation of α-synuclein, however, is unclear.</p> <p>Results</p> <p>Here we show that PD-related A53T mutant α-synuclein, when selectively expressed in astrocytes, induced rapidly progressed paralysis in mice. Increasing accumulation of α-synuclein aggregates was found in presymptomatic and symptomatic mouse brains and correlated with the expansion of reactive astrogliosis. The normal function of astrocytes was compromised as evidenced by cerebral microhemorrhage and down-regulation of astrocytic glutamate transporters, which also led to increased inflammatory responses and microglial activation. Interestingly, the activation of microglia was mainly detected in the midbrain, brainstem and spinal cord, where a significant loss of dopaminergic and motor neurons was observed. Consistent with the activation of microglia, the expression level of cyclooxygenase 1 (COX-1) was significantly up-regulated in the brain of symptomatic mice and in cultured microglia treated with conditioned medium derived from astrocytes over-expressing A53T α-synuclein. Consequently, the suppression of COX-1 activities extended the survival of mutant mice, suggesting that excess inflammatory responses elicited by reactive astrocytes may contribute to the degeneration of neurons.</p> <p>Conclusions</p> <p>Our findings demonstrate a critical involvement of astrocytic α-synuclein in initiating the non-cell autonomous killing of neurons, suggesting the viability of reactive astrocytes and microglia as potential therapeutic targets for PD and other neurodegenerative diseases.</p
Tidal Love numbers of Axion stars
We investigate the tidal deformability of spherically symmetric axion stars
on the stable branches, including the Newtonian and relativistic branches. The
results suggest that on the stable branch, the electric Love numbers of axion
star are positive, while the magnetic Love numbers are negative. On the
Newtonian stable branch, the electric tidal Love numbers are much larger than
the magnetic ones, while on the relativistic stable branch, they are slightly
larger. Furthermore, the relativistic stable branch has much smaller tidal Love
numbers than the Newtonian stable branch, indicating weaker deformability of
axion stars on the relativistic stable branch. This could be attributed to the
fact that on the relativistic branch, axion stars are more compact, resulting
hardly distorted by tidal forces.Comment: 22 pages, 5 figure
Excited Dirac stars with higher azimuthal harmonic index
In this paper, we investigate the properties of the first excited state Dirac
stars (DSs) with higher azimuthal harmonic index (specifically, the azimuthal
harmonic indexes = , , ), as well as the relationship
between the ADM mass and angular momentum of Dirac stars with respect to
frequency. Moreover, We find that the ergospheres of DSs appear at lower spinor
field frequencies, and both the ergospheres and the distribution of the spinor
field functions are asymmetric about the equatorial plane. Furthermore, we
introduce the ground state scalar field and examine its impact on this system,
which is known as the multi-state Dirac-boson stars (DBSs) model. We show
various types of solution families for DBSs under both synchronized frequency
and nonsynchronized frequencies and find that similar to DSs, the
spinor field and the ergospheres of DBSs are also asymmetric about the
equatorial plane, but the ergospheres appear at higher spinor field
frequencies.Comment: 22 pages, 8 figure
Quantum Andreev effect in 2D HgTe/CdTe quantum well-superconductor systems
The Andreev reflection (AR) in 2D HgTe/CdTe quantum well-superconductor
hybrid systems is studied. A quantized AR with AR coefficient equal to one is
predicted, which is due to the multi-Andreev reflection near the interface of
the hybrid system. Importantly, this quantized AR is not only universal, i.e.,
independent of any system parameters and quality of the coupling of the hybrid
system, it is also robust against disorder as well. As a result of this quantum
Andreev effect, the conductance exhibits a quantized plateau when the external
bias is less the superconductor gap.Comment: submit to Phys. Rev. Lett. on Jul. 16, 201
Symmetries and Lie algebra of the differential-difference Kadomstev-Petviashvili hierarchy
By introducing suitable non-isospectral flows we construct two sets of
symmetries for the isospectral differential-difference Kadomstev-Petviashvili
hierarchy. The symmetries form an infinite dimensional Lie algebra.Comment: 9 page
Emergency of black holes from wormholes
In this paper, we study the spherically symmetric Dirac star model in the
presence of a phantom field, obtaining a traversable wormhole solution in
non-trivial topological spacetime. This solution exhibits asymmetry in both the
field configuration and the metric and possesses a finite ADM mass and
Noether charge . Furthermore, we find that due to the presence of a wormhole
at the center, this solution exhibits many differences from the Dirac star
under trivial spacetime. Notably, when the wormhole throat size is small, our
numerical calculations indicate the emergence of an extremely approximate black
hole solution on one side of the wormhole spacetime, a phenomenon unexplored.
At this time, the Kretschmann scalar near the throat tends to infinity,
indicating the wormhole becomes untraversable.Comment: 32 pages, 23 figure
Nuclear structure of 178Hf related to the spin-16, 31-year isomer
The projected shell model is used to study the multi-quasiparticle and
collective excitations of 178Hf. With an axially symmetric basis, the spin-16
isomer at 2.4 MeV appears to be well separated in energy/spin space from other
configurations. However, projected energy surface calculations suggest that
178Hf has significant softness to axially asymmetric shapes, which can strongly
modify the level distribution. The implications for photodeexitation of the
isomer are discussed.Comment: 8 pages, 4 figure
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