DSpace コレクション:
http://hdl.handle.net/2433/48879
2019-03-22T18:05:10ZCosmological models with the energy density of random fluctuations and the Hubble-constant problem
http://hdl.handle.net/2433/237299
タイトル: Cosmological models with the energy density of random fluctuations and the Hubble-constant problem
著者: Tomita, Kenji
抄録: The fluctuation energy is derived from adiabatic random fluctuations due to second-order perturbation theory, and the evolutionary relation for it is expressed in the form of ρf = ρf (ρ), where ρ and ρf are the densities of ordinary dust and the fluctuation energy, respectively. The pressureless matter as a constituent of the universe at the later stage is assumed to consist of ordinary dust and the fluctuation energy. Next, cosmological models including the fluctuation energy as a kind of dark matter are derived using the above relation, and it is found that the Hubble parameter and the other model parameters in the derived models can be consistent with the recent observational values. Moreover, the perturbations of ρ and ρf are studied.2017-08-01T00:00:00ZCanonical tensor model through data analysis: Dimensions, topologies, and geometries
http://hdl.handle.net/2433/236677
タイトル: Canonical tensor model through data analysis: Dimensions, topologies, and geometries
著者: Kawano, Taigen; Obster, Dennis; Sasakura, Naoki
抄録: The canonical tensor model (CTM) is a tensor model in Hamilton formalism and is studied as a model for gravity in both classical and quantum frameworks. Its dynamical variables are a canonical conjugate pair of real symmetric three-index tensors, and a question in this model was how to extract spacetime pictures from the tensors. We give such an extraction procedure by using two techniques widely known in data analysis. One is the tensor-rank (or CP etc.) decomposition, which is a certain generalization of the singular value decomposition of a matrix and decomposes a tensor into a number of vectors. By regarding the vectors as points forming a space, topological properties are extracted by using the other data analysis technique called persistent homology, and geometries by virtual diffusion processes over points. Thus, time evolutions of the tensors in the CTM can be interpreted as topological and geometric evolutions of spaces. We have performed some initial investigations of the classical equation of motion of the CTM in terms of these techniques for a homogeneous fuzzy circle and homogeneous two- and three-dimensional fuzzy spheres as spaces, and have obtained agreement with the general relativistic system obtained previously in a formal continuum limit of the CTM. It is also demonstrated by some concrete examples that the procedure is general for any dimensions and topologies, showing the generality of the CTM.2018-06-15T00:00:00ZMuon g-2 and α (MZ2): A new data-based analysis
http://hdl.handle.net/2433/236674
タイトル: Muon g-2 and α (MZ2): A new data-based analysis
著者: Keshavarzi, Alexander; Nomura, Daisuke; Teubner, Thomas
抄録: This work presents a complete reevaluation of the hadronic vacuum polarization contributions to the anomalous magnetic moment of the muon, aμhad, VP, and the hadronic contributions to the effective QED coupling at the mass of the Z boson, Δαhad(MZ2), from the combination of e+e-→hadrons cross section data. Focus has been placed on the development of a new data combination method, which fully incorporates all correlated statistical and systematic uncertainties in a bias free approach. All available e+e-→hadrons cross section data have been analyzed and included, where the new data compilation has yielded the full hadronic R-ratio and its covariance matrix in the energy range mπ≤s≤11.2 GeV. Using these combined data and perturbative QCD above that range results in estimates of the hadronic vacuum polarization contributions to g-2 of the muon of aμhad, LO VP=(693.26±2.46)×10-10 and aμhad, NLO VP=(-9.82±0.04)×10-10. The new estimate for the Standard Model prediction is found to be aμSM=(11659182.04±3.56)×10-10, which is 3.7σ below the current experimental measurement. The prediction for the five-flavor hadronic contribution to the QED coupling at the Z boson mass is Δαhad(5)(MZ2)=(276.11±1.11)×10-4, resulting in α-1(MZ2)=128.946±0.015. Detailed comparisons with results from similar related works are given2018-06-25T00:00:00ZAspects of massive gauge theories on three sphere in infinite mass limit
http://hdl.handle.net/2433/236426
タイトル: Aspects of massive gauge theories on three sphere in infinite mass limit
著者: Shimizu, Kazuma
抄録: We study the S3 partition function of three-dimensional supersymmetric N=4 U(N) SQCD with massive matter multiplets in the infinite mass limit with the so-called Coulomb branch localization. We show that in the infinite mass limit a specific point of the Coulomb branch is selected and contributes dominantly to the partition function. Therefore, we can argue whether each multiplet included in the theory is effectively massless in this limit, even on S3, and conclude that the partition function becomes that of the effective theory on the specific point of the Coulomb branch in the infinite mass limit. In order to investigate which point of the Coulomb branch is dominant, we use the saddle point approximation in the large N limit because the solution of the saddle point equation can be regarded as a specific point of the Coulomb branch. Then, we calculate the partition functions for small rank N and confirm that their behaviors in the infinite mass limit are consistent with the conjecture from the results in the large N limit. Our result suggests that the partition function in the infinite mass limit corresponds to that of an interacting superconformal field theory.2019-01-01T00:00:00Z