The stability of modified gravity models

Conditions for the existence and stability of de Sitter space in modified gravity are derived by considering inhomogeneous perturbations in a gauge-invariant formalism. The stability condition coincides with the corresponding condition for stability with respect to homogeneous perturbations, while this is not the case in scalar-tensor gravity. The stability criterion is applied to various modified gravity models of the early and the present universe.Comment: 22 pages, LaTeX, to appear in Phys. Rev.

Development of singularities for the compressible Euler equations with external force in several dimensions

We consider solutions to the Euler equations in the whole space from a certain class, which can be characterized, in particular, by finiteness of mass, total energy and momentum. We prove that for a large class of right-hand sides, including the viscous term, such solutions, no matter how smooth initially, develop a singularity within a finite time. We find a sufficient condition for the singularity formation, "the best sufficient condition", in the sense that one can explicitly construct a global in time smooth solution for which this condition is not satisfied "arbitrary little". Also compactly supported perturbation of nontrivial constant state is considered. We generalize the known theorem by Sideris on initial data resulting in singularities. Finally, we investigate the influence of frictional damping and rotation on the singularity formation.Comment: 23 page

Low-Frequency Quantum Sensing

低周波信号の新規高感度量子センシング手法を開発 --NV量子センサを用いた核磁気共鳴（NMR）世界最小線幅を実証--. 京都大学プレスリリース. 2022-11-01.Exquisite sensitivities are a prominent advantage of quantum sensors. Ramsey sequences allow precise measurement of direct current fields, while Hahn-echo-like sequences measure alternating current fields. However, the latter are restrained for use with high-frequency fields (above approximately 1kHz) due to finite coherence times, leaving less-sensitive noncoherent methods for the low-frequency range. In this paper, we propose to bridge the gap with a fitting-based algorithm with a frequency-independent sensitivity to coherently measure low-frequency fields. As the algorithm benefits from coherence-based measurements, its demonstration with a single nitrogen-vacancy center gives a sensitivity of 9.4nT Hz⁻⁰.⁵ for frequencies below about 0.6kHz down to near-constant fields. To inspect the potential in various scenarios, we apply the algorithm at a background field of tens of nTs, and we measure low-frequency signals via synchronization

Infestação de plantas daninhas em cultivos de milho safrinha em função de híbridos e populações de plantas em espaçamento reduzido.

JIPE 2013

Fermi Surface of 3d^1 Perovskite CaVO3 Near the Mott Transition

We present a detailed de Haas van Alphen effect study of the perovskite CaVO3, offering an unprecedented test of electronic structure calculations in a 3d transition metal oxide. Our experimental and calculated Fermi surfaces are in good agreement -- but only if we ignore large orthorhombic distortions of the cubic perovskite structure. Subtle discrepancies may shed light on an apparent conflict between the low energy properties of CaVO3, which are those of a simple metal, and high energy probes which reveal strong correlations that place CaVO3 on the verge of a metal-insulator transition.Comment: 4 pages, 4 figures (REVTeX

Statistical properties of spectral fluctuations for a quantum system with infinitely many components

Extending the idea formulated in Makino {\it{et al}}[Phys.Rev.E {\bf{67}},066205], that is based on the Berry--Robnik approach [M.V. Berry and M. Robnik, J. Phys. A {\bf{17}}, 2413], we investigate the statistical properties of a two-point spectral correlation for a classically integrable quantum system. The eigenenergy sequence of this system is regarded as a superposition of infinitely many independent components in the semiclassical limit. We derive the level number variance (LNV) in the limit of infinitely many components and discuss its deviations from Poisson statistics. The slope of the limiting LNV is found to be larger than that of Poisson statistics when the individual components have a certain accumulation. This property agrees with the result from the semiclassical periodic-orbit theory that is applied to a system with degenerate torus actions[D. Biswas, M.Azam,and S.V.Lawande, Phys. Rev. A {\bf 43}, 5694].Comment: 6 figures, 10 page

Changes in the long term intensity variations in Cyg X-2 and LMC X-3

We report the detection of changes in the long-term intensity variations in two X-ray binaries, Cyg X-2 and LMC X-3. In this work, we have used the long-term light curves obtained with the All-Sky Monitors (ASMs) of the Rossi X-Ray Timing Explorer (RXTE), Ginga, Ariel 5, and Vela 5B and the scanning modulation collimator of HEAO 1. It is found that in the light curves of both the sources, obtained with these instruments at various times over the last 30 years, more than one periodic or quasi-periodic component is always present. The multiple prominent peaks in the periodograms have frequencies unrelated to each other. In Cyg X-2, RXTE-ASM data show strong peaks at 40.4 and 68.8 days, and Ginga-ASM data show strong peaks at 53.7 and 61.3 days. Multiple peaks are also observed in LMC X-3. The various strong peaks in the periodograms of LMC X-3 appear at 104, 169, and 216 days (observed with RXTE-ASM) and 105, 214, and 328 days (observed with Ginga-ASM). The present results, when compared with the earlier observations of periodicities in these two systems, demonstrate the absence of any stable long period. The 78 day periodicity detected earlier in Cyg X-2 was probably due to the short time base in the RXTE data that were used, and the periodicity of 198 days in LMC X-3 was due to a relatively short duration of observation with HEAO 1.Comment: 11 pages, 7 postscript figures include

Chaotic inflation with running nonminimal coupling

We have found a successful model of chaotic inflation with an inflaton coupled nonminimally with gravity. The nonminimal coupling constant $\xi$ runs with the evolution of the inflaton. The running nature of the coupling leads naturally to the situations where the coupling becomes small enough to have sufficient period of the inflation to resolve the cosmological puzzles.Comment: 9 pages, Latex, 2 Figures. In Introduction and Discussion Comments on the related works are changed and added appropriately. References are added for completenes

Efficacy of conversion gastrectomy following docetaxel, cisplatin, and S-1 therapy in potentially resectable stage IV gastric cancer

AbstractBackgroundRecent advances in gastric cancer chemotherapy have made macroscopic complete resection possible in some patients with stage IV disease.MethodsWe retrospectively investigated the efficacy of multimodal therapy with combined docetaxel, cisplatin, and S-1 (DCS) and conversion gastrectomy in 57 patients with stage IV gastric cancer.ResultsOf the 57 patients, 15 patients were categorized into potentially resectable case, which is defined as patients with single incurable factor including the upper abdominal para-aortic lymph node metastasis (16a2b1 PAN metastasis) or fewer than three peripheral liver metastases. The other 42 were categorized as initially unresectable. All of patients underwent DCS therapy, and then 34 patients underwent conversion gastrectomy. The 3-year overall survival (OS) rate among the patients who underwent conversion gastrectomy was 50.1% with MST of 29.9 months. They had significantly longer OS than patients who underwent DCS therapy alone (p < 0.01). Univariate analysis among the patents with conversion gastrectomy identified 16a2b1PAN metastasis, peritoneal metastasis, potential resectable case, R0 resection as significant prognostic factors. A 3-year OS in potential resectable cases was 92.9%. Multivariate analysis identified potential resectability as the only independent prognostic factor contributing to OS (HR 0.133, 95%CI 0.024-0. 744, p = 0.021). In contrast, clinical response was selected as the only independent prognostic factor in the subgroup of initially unresectable cases (HR 0.354, 95%CI 0.151-0.783, p = 0.021).ConclusionPatients with potentially resectable disease had a remarkably good prognosis among stage IV gastric cancer patients, and might be ideal candidates for conversion gastrectomy following DCS therapy

Detection of Anthrax Spores from the Air by Real-Time PCR

炭疽菌によるエアロゾル汚染防止対策の一環として、炭疽菌芽胞を大気と共に吸引してメンブランフィルターに回収し、その検出をリアルタイムPCRで行った。本システムにより、10個の芽胞を1時間以内に検出することができ、その結果は培養試験による結果と完全に一致した