Weak gravity conjecture constraints on inflation

We consider the gravitational correction to the coupling of the scalar fields. Weak gravity conjecture says that the gravitational correction to the running of scalar coupling should be less than the contribution from scalar fields. For instance, a new scale $\Lambda=\lambda_4^{1/2}M_p$ sets a UV cutoff on the validity of the effective $\lambda_4 \phi^4$ theory. Furthermore, this conjecture implies a possible constraint on the inflation model, e.g. the chaotic inflation model might be in the swampland.Comment: 11 pages, 3 figs; monor corrections; some clarifying remarks added and the final version for publication in JHE

Interacting non-minimally coupled canonical, phantom and quintom models of holographic dark energy in non-flat universe

Motivated by our recent work \cite{set1}, we generalize this work to the interacting non-flat case. Therefore in this paper we deal with canonical, phantom and quintom models, with the various fields being non-minimally coupled to gravity, within the framework of interacting holographic dark energy. We employ the holographic model of interacting dark energy to obtain the equation of state for the holographic energy density in non-flat (closed) universe enclosed by the event horizon measured from the sphere of horizon named $L$.Comment: 18 pages, 3 figures. Accepted for publication in IJMPD (2010

Gravitational Correction and Weak Gravity Conjecture

We consider the gravitational correction to the running of gauge coupling. Weak gravity conjecture implies that the gauge theories break down when the gravitational correction becomes greater than the contribution from gauge theories. This observation can be generalized to non-Abelian gauge theories in diverse dimensions and the cases with large extra dimensions.Comment: 8 pages; minor correction and refs adde

Holographic interacting dark energy in the braneworld cosmology

We investigate a model of brane cosmology to find a unified description of the radiation-matter-dark energy universe. It is of the interacting holographic dark energy with a bulk-holographic matter $\chi$. This is a five-dimensional cold dark matter, which plays a role of radiation on the brane. Using the effective equations of state $\omega^{\rm eff}_{\rm \Lambda}$ instead of the native equations of state $\omega_{\rm \Lambda}$, we show that this model cannot accommodate any transition from the dark energy with $\omega^{\rm eff}_{\rm \Lambda}\ge-1$ to the phantom regime $\omega^{\rm eff}_{\rm \Lambda}<-1$. Furthermore, the case of interaction between cold dark matter and five dimensional cold dark matter is considered for completeness. Here we find that the redshift of matter-radiation equality $z_{\rm eq}$ is the same order as $z^{\rm ob}_{\rm eq}=2.4\times10^{4} \Omega_{\rm m}h^2$. Finally, we obtain a general decay rate $\Gamma$ which is suitable for describing all interactions including the interaction between holographic dark energy and cold dark matter.Comment: 17 pages, 4 figure

The Measure for the Multiverse and the Probability for Inflation

We investigate the measure problem in the framework of inflationary cosmology. The measure of the history space is constructed and applied to inflation models. Using this measure, it is shown that the probability for the generalized single field slow roll inflation to last for $N$ e-folds is suppressed by a factor $\exp(-3N)$, and the probability for the generalized $n$-field slow roll inflation is suppressed by a much larger factor $\exp(-3nN)$. Some non-inflationary models such as the cyclic model do not suffer from this difficulty.Comment: 16 page

Eternal Chaotic Inflation is Prohibited by Weak Gravity Conjecture

We investigate whether the eternal chaotic inflation can be achieved when the weak gravity conjecture is taken into account. We show that even the assisted chaotic inflation with potential $\lambda\phi^4$ or $m^2\phi^2$ can not be eternal. The effective field theory description for the inflaton field breaks down before inflation reaches the eternal regime. We also find that the total number of e-folds is still bounded by the inflationary entropy for the assisted inflation.Comment: 10 page

Fe-based superconductors: unity or diversity?

Does the high temperature superconductivity observed in the newly discovered iron-pnictide materials represent another example of the same essential physics responsible for superconductivity in the cuprates, or does it embody a new mechanism?Comment: Some minor errors in the figure and in the reference in the published version are corrected. 2 pages, 2 figure

Formation of Long Single Quantum Dots in High Quality InSb Nanowires Grown by Molecular Beam Epitaxy

We report on realization and transport spectroscopy study of single quantum dots (QDs) made from InSb nanowires grown by molecular beam epitaxy (MBE). The nanowires employed are 50-80 nm in diameter and the QDs are defined in the nanowires between the source and drain contacts on a Si/SiO$_2$ substrate. We show that highly tunable QD devices can be realized with the MBE-grown InSb nanowires and the gate-to-dot capacitance extracted in the many-electron regimes is scaled linearly with the longitudinal dot size, demonstrating that the devices are of single InSb nanowire QDs even with a longitudinal size of ~700 nm. In the few-electron regime, the quantum levels in the QDs are resolved and the Land\'e g-factors extracted for the quantum levels from the magnetotransport measurements are found to be strongly level-dependent and fluctuated in a range of 18-48. A spin-orbit coupling strength is extracted from the magnetic field evolutions of a ground state and its neighboring excited state in an InSb nanowire QD and is on the order of ~300 $\mu$eV. Our results establish that the MBE-grown InSb nanowires are of high crystal quality and are promising for the use in constructing novel quantum devices, such as entangled spin qubits, one-dimensional Wigner crystals and topological quantum computing devices.Comment: 19 pages, 5 figure