1,340 research outputs found
Where does curvaton reside? Differences between bulk and brane frames
Some classes of inflationary models naturally introduce two distinct
metrics/frames, and their equivalence in terms of observables has often been
put in question. D-brane inflation proposes candidates for an inflaton embedded
in the string theory and possesses descriptions on the brane and bulk
metrics/frames, which are connected by a conformal/disformal transformation
that depends on the inflaton and its derivatives. It has been shown that
curvature perturbations generated by the inflaton are identical in both frames,
meaning that observables such as the spectrum of cosmic microwave background
(CMB) anisotropies are independent of whether matter fields---including those
in the standard model of particle physics---minimally couple to the brane or
the bulk metric/frame. This is true despite the fact that the observables are
eventually measured by the matter fields and that the total action including
the matter fields is different in the two cases. In contrast, in curvaton
scenarios, the observables depend on the frame to which the curvaton minimally
couples. Among all inflationary scenarios, we focus on two models motivated by
the KKLMMT fine-tuning problem: a slow-roll inflation with an inflection-point
potential and a model of a rapidly rolling inflaton that conformally couples to
gravity. In the first model, the difference between the frames in which the
curvaton resides is encoded in the spectral index of the curvature
perturbations, depicting the nature of the frame transformation. In the second
model, the curvaton on the brane induces a spectral index significantly
different from that in the bulk and is even falsified by the observations. This
work thus demonstrates that two frames connected by a conformal/disformal
transformation lead to different physical observables such as CMB anisotropies
in curvaton models.Comment: 16 pages, v2: published versio
Spin-state transition and phase separation in multi-orbital Hubbard model
We study spin-state transition and phase separation involving this transition
based on the milti-orbital Hubbard model. Multiple spin states are realized by
changing the energy separation between the two orbitals and the on-site Hund
coupling. By utilizing the variational Monte-Carlo simulation, we analyze the
electronic and magnetic structures in hole doped and undoped states. Electronic
phase separation occurs between the low-spin band insulating state and the
high-spin ferromagnetic metallic one. Difference of the band widths in the two
orbitals is of prime importance for the spin-state transition and the phase
separation.Comment: 5 pages, 5 figure
Simple Estimation Model and Energy-efficient Virtual Machine Migration Algorithm in a Server Cluster
In this thesis, we propose a virtual machine migration approach to reducing the electric energy consumption of servers. In our previous algorithms, one virtual machine migrates from a host server to a guest server. While the electric energy consumption of servers can be reduced by migrating some number b of processes, there might not be a virtual machine with the same number b of processes on a host server. In this thesis, we newly propose an ISEAM2T algorithm where multiple virtual machines can migrate from a host server to a guest server. Here, multiple virtual machines on a host server are selected so that the total number of processes on the virtual machines can be more easily adjusted to the optimal number b of processes. In the evaluation, we show the total electric energy consumption and active time of the servers can be reduced in the proposed algorithm
A rule for anticipatory action planning for stepping onto two potential targets
東京都立大学Tokyo Metropolitan University博士(学術)doctoral thesi
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