DSpace Community:
http://hdl.handle.net/2433/48878
2019-08-24T00:16:35ZA random matrix model with non-pairwise contracted indices
http://hdl.handle.net/2433/243192
Title: A random matrix model with non-pairwise contracted indices
Authors: Lionni, Luca; Sasakura, Naoki
Abstract: We consider a random matrix model with both pairwise and non-pairwise contracted indices. The partition function of the matrix model is similar to that appearing in some replicated systems with random tensor couplings, such as the p-spin spherical model for the spin glass. We analyze the model using Feynman diagrammatic expansions, and provide an exhaustive characterization of the graphs that dominate when the dimensions of the pairwise and (or) non-pairwise contracted indices are large. We apply this to investigate the properties of the wave function of a toy model closely related to a tensor model in the Hamilton formalism, which is studied in a quantum gravity context, and obtain a result in favor of the consistency of the quantum probabilistic interpretation of this tensor model.2019-07-01T00:00:00ZHeterotic string field theory and new relations extending L ∞ algebra
http://hdl.handle.net/2433/241557
Title: Heterotic string field theory and new relations extending L ∞ algebra
Authors: Kunitomo, Hiroshi
Abstract: Based on the Wess-Zumino-Witten-like formulation, a gauge invariant action for heterotic string field theory is constructed at the sixth and eighth order of the Ramond field Ψ. A key relation is a kind of extension of the L ∞ algebra including another type of string products called the gauge products. Some general structure of a complete action is also discussed.
Description: The 32nd International Colloquium on Group Theoretical Methods in Physics (Group32): 9-13 July 2018, Prague, Czech Republic2019-04-24T00:00:00ZCosmological models with the energy density of random fluctuations and the Hubble-constant problem
http://hdl.handle.net/2433/237299
Title: Cosmological models with the energy density of random fluctuations and the Hubble-constant problem
Authors: Tomita, Kenji
Abstract: 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
Title: Canonical tensor model through data analysis: Dimensions, topologies, and geometries
Authors: Kawano, Taigen; Obster, Dennis; Sasakura, Naoki
Abstract: 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.2018-06-15T00:00:00Z