The Quantum Matter Study Group invited Prof. Rafael Nepomechie from the University of Miami to talk about the Bethe ansatz and realizing Bethe states in quantum computers. In the beginning, he used the Heisenberg chain to introduce the coordinate Bethe ansatz. In condensed matter physics, it is extremely difficult to solve many-body Hamiltonians. For this specific Heisenberg model, Bethe came up with a judicious method for finding the exact many-body wave function. The many-body problem is transformed to solving the Bethe equations. Unfortunately, it is also hard to solve these equations completely. Prof. Nepomechie presented an alternative approach to find the exact wave function and hence the solution to the Bethe equations through quantum computation. He found that, by using specific quantum operations, the exact wave function of the Heisenberg model can be presented in the quantum computer with a probability decaying as the factorial of the number magnons that make up the wave function. It is interesting to learn about this connection between the Bethe ansatz and quantum computing. Discussions were made how to increase the probability of the discussed scheme and how to extend it to find the complete set of Bethe roots for larger systems.

Reported by Thore Posske (University of Hamburg, Germany) and Ching-Kai Chiu

We successfully had a great time thanks to Dr. Kenta Ishimoto's fantastic talk, in which he talked about the basic background of fluid dynamics, followed by two topics of his own research. Thank you again for the fantastic talk!

Reported by Ryosuke Iritani

Weakly Interacting Massive Particles (WIMPs) have long been a leading candidate of dark matter(DM). However, no signatures are found in any kinds of experiments. Investigation of the alternatives is now rapidly growing. Primordial black holes (PBHs), which are formed in the early Universe and source the gravitational potential for baryonic components to evolve, are being widely discussed and searched now.

Recent progress of the gravitational, as well as electromagnetic, observations of the Universe already excludes a large portion of the parameter space of PBH as DM. So if it contributes to DM, it is natural to also consider contributions from other components such as WIMPs. In such a situation, PBHs are dressed with WIMP halos. Then WIMP annihilation proceeds in the vicinity of the central PBH and a cored structure is expected depending on the annihilation rate. This dependence of the core structure on the annihilation rate leads to a tricky behavior in the constraints for PBH-WIMP mixed scenarios.

Also, when PBHs are abundantly formed, we cannot neglect their clustering effects on the constraints obtained in the observable Universe because the dressed PBH with WIMP indicates the clustering of WIMP halos in host galaxies. In this case, the boost factor, which appears naturally in the scenario of pure WIMP DM models, needs to be evaluated in such a way that regarding the clustering of PBHs.

Those interesting phenomena are only a part of examples that we can expect in the PBH-WIMP mixed scenario for DM. Varieties of possibilities are waiting for our investigations. Discussions are blooming now!

Reported by Nagisa Hiroshima

Authors: Robert Poulin
Translation: Hirotaka Katahira, Ryota Kawanishi and Ryosuke Iritani
Language: Japanese

Translated from "Evolutionary Ecology of Parasites: Second Edition" ( Princeton University Press, 2007) by Robert Poulin

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