51,015 research outputs found

    Weak gravity conjecture constraints on inflation

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    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 Λ=λ41/2Mp\Lambda=\lambda_4^{1/2}M_p sets a UV cutoff on the validity of the effective λ4ϕ4\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

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    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 LL.Comment: 18 pages, 3 figures. Accepted for publication in IJMPD (2010

    Gravitational Correction and Weak Gravity Conjecture

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    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

    The Measure for the Multiverse and the Probability for Inflation

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    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 NN e-folds is suppressed by a factor exp(3N)\exp(-3N), and the probability for the generalized nn-field slow roll inflation is suppressed by a much larger factor exp(3nN)\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

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    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 λϕ4\lambda\phi^4 or m2ϕ2m^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?

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    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

    Parity independence of the zero-bias conductance peak in a nanowire based topological superconductor-quantum dot hybrid device

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    We explore the signatures of Majorana fermions in a nanowire based topological superconductor-quantum dot-topological superconductor hybrid device by charge transport measurements. The device is made from an epitaxially grown InSb nanowire with two superconductor Nb contacts on a Si/SiO2_2 substrate. At low temperatures, a quantum dot is formed in the segment of the InSb nanowire between the two Nb contacts and the two Nb contacted segments of the InSb nanowire show superconductivity due to the proximity effect. At zero magnetic field, well defined Coulomb diamonds and the Kondo effect are observed in the charge stability diagram measurements in the Coulomb blockade regime of the quantum dot. Under the application of a finite, sufficiently strong magnetic field, a zero-bias conductance peak structure is observed in the same Coulomb blockade regime. It is found that the zero-bias conductance peak is present in many consecutive Coulomb diamonds, irrespective of the even-odd parity of the quasi-particle occupation number in the quantum dot. In addition, we find that the zero-bias conductance peak is in most cases accompanied by two differential conductance peaks, forming a triple-peak structure, and the separation between the two side peaks in bias voltage shows oscillations closely correlated to the background Coulomb conductance oscillations of the device. The observed zero-bias conductance peak and the associated triple-peak structure are in line with the signatures of Majorana fermion physics in a nanowire based topological superconductor-quantum dot-topological superconductor system, in which the two Majorana bound states adjacent to the quantum dot are hybridized into a pair of quasi-particle states with finite energies and the other two Majorana bound states remain as the zero-energy modes located at the two ends of the entire InSb nanowire.Comment: 6 pages, 4 figure
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