8,868 research outputs found
Ge Nanowires Anode sheathed with Amorphous Carbon for Rechargeable Lithium batteries
Interdisciplinary School of Green EnergyThe composite electrode composed of single crystalline Ge NWs sheathed with amorphous carbon showed excellent electrochemical properties of large reversible capacity, high coulombic efficiency, excellent rate capability and stable cycle performance. c-Ge NWs synthesized by using thermal decomposition of C2H2 gas at 700 ยฐC under Ar atmosphere after SLS (solution-liquid-solid) growth were found to have good performance during cycling with Li. The rate capability for charging was shown reversible capacity of 963 mAh/g with a coulombic efficiency of 90% and 700 mAh/g at the rate of 6C (= 4800mA/g). Capacity retention after 100 cycles was 72% at the rate of 0.5C. The improved electrochemical performance of c-Ge-NWs fabricated in our experiment was attributed to the formation of amorphous Ge NWs during cycling and a homogenous carbon coating on Ge NWs. Thus, these results suggest that the use of nanowires structure can be promising for alloy anode materials in lithium ion batteries
Communication with SIMP dark mesons via Z'-portal
We consider a consistent extension of the SIMP models with dark mesons by
including a dark U(1)_D gauge symmetry. Dark matter density is determined by a
thermal freeze-out of the self-annihilation process, thanks to the
Wess-Zumino-Witten term. In the presence of a gauge kinetic mixing between the
dark photon and the SM hypercharge gauge boson, dark mesons can undergo a
sufficient scattering off the Standard Model particles and keep in kinetic
equilibrium until freeze-out in this SIMP scenario. Taking the
SU(N_f)xSU(N_f)/SU(N_f) flavor symmetry under the SU(N_c) confining group, we
show how much complementary the SIMP constraints on the parameters of the dark
photon are for current experimental searches for dark photon.Comment: 16 pages, 6 figures, To appear in Phys. Lett.
SIMP dark matter and its cosmic abundances
We give a review on the thermal average of the annihilation cross-sections
for and general higher-order processes. Thermal average of
higher order annihilations highly depend on the velocity of dark matter,
especially, for the case with resonance poles. We show such examples for scalar
dark matter in gauged models.Comment: 5 pages, 2 figures, Prepared for the proceedings of the 13th
International Conference on Gravitation, 3-7 July 201
Cosmic abundances of SIMP dark matter
Thermal production of light dark matter with sub-GeV scale mass can be
attributed to self-annihilation processes. We consider the
thermal average for annihilation cross sections of dark matter at and general higher-order interactions. A correct thermal average for initial
dark matter particles is important, in particular, for annihilation cross
sections with overall velocity dependence and/or resonance poles. We apply our
general results to benchmark models for SIMP dark matter and discuss the
effects of the resonance pole in determining the relic density.Comment: 21 pages, 6 figures, Version to appear in Journal of High Energy
Physic
Consistency relations in multi-field inflation
We study the consequences of spatial coordinate transformation in multi-field
inflation. Among the spontaneously broken de Sitter isometries, only dilatation
in the comoving gauge preserves the form of the metric and thus results in
quantum-protected Slavnov-Taylor identities. We derive the corresponding
consistency relations between correlation functions of cosmological
perturbations in two different ways, by the connected and
one-particle-irreducible Green's functions. The lowest-order consistency
relations are explicitly given, and we find that even in multi-field inflation
the consistency relations in the soft limit are independent of the detail of
the matter sector.Comment: 24 pages, version to appear in JCA
A solvent-free Diels-Alder reaction of graphite into functionalized graphene nanosheets
A solvent-free Diels-Alder reaction was carried out by heating a mixture of graphite and a typical dienophile, maleic anhydride (MA) or maleimide (MI), in a sealed glass ampoule of argon. The functionalization of graphite with dienophiles was confirmed by various characterization techniques, suggesting the efficient functionalization and delamination of graphite into a few layers of graphitic nanosheets.close0
Quantum non-linear evolution of inflationary tensor perturbations
We study the quantum mechanical evolution of the tensor perturbations during
inflation with non-linear tensor interactions. We first obtain the Lindblad
terms generated by non-linear interactions by tracing out unobservable
sub-horizon modes. Then we calculate explicitly the reduced density matrix for
the super-horizon modes, and show that the probability of maintaining the
unitarity of the squeezed state decreases in time. The decreased probability is
transferred to other elements of the reduced density matrix including
off-diagonal ones, so the evolution of the reduced density matrix describes the
quantum-to-classical transition of the tensor perturbations. This is different
from the classicality accomplished by the squeezed state, the suppression of
the non-commutative effect, which is originated from the quadratic, linear
interaction, and also maintains the unitarity. The quantum-to-classical
transition occurs within 5 - 10 e-folds, faster than the curvature
perturbation.Comment: (v1) 39 pages, (v2) typos corrected, to be published in Journal of
High Energy Physic
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