iTHEMS Weekly News Letter

Featured Paper of the Week

Distance between collapsing matter and trapping horizon in evaporating black holes


How deep can an apple fall into the horizon of a black hole? Of course, in the case of a classic black hole, the apple reaches the center. However, the real world is described by quantum theory, and black holes evaporate by Hawking radiation. This changes the fate of the apple. Negative energy due to vacuum quantum fluctuations is generated near black holes, which enters the black holes and reduces their energy. If there is a horizon, the negative energy will make the horizon smaller. Then, the horizon becomes timelike (while it is null in the classical case). In this paper, we solved approximately the Einstein equation in the vicinity of the horizon and examined the physical (proper) distance between the falling apple and the horizon. It turned out that the distance is a few of the Planck length (due to the exponentially delayed time inside the horizon). This means that essentially no apples fall into the black hole. This result suggest that we should reconsider whether the black hole really has a horizon.

Pei-Ming Ho, Yoshinori Matsuo, Yuki Yokokura
"Distance between collapsing matter and trapping horizon in evaporating black holes"
arXiv: 1912.12863

Upcoming Events


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ABBL-iTHEMS Joint Seminar

ABBL/iTHEMS seminar - talk on neutron stars

January 24 at 14:00 - 15:00, 2020

Dr. Hajime Sotani (Research Scientist, iTHEMS / Research Scientist, Astrophysical Big Bang Laboratory, RIKEN Cluster for Pioneering Research (CPR))

Venue: Seminar Room #132

Event Official Language: English


CREST Tutorial Workshop

January 26 - 28, 2020

This workshop is co-organized by CREST Research Project "[Topology] Creation of Core Technology based on the Topological Materials Science for Innovative Devices" and RIKEN iTHEMS.

Venue: Graduate School of Mathematical Sciences, The University of Tokyo

Event Official Language: Japanese


ABBL-iTHEMS Joint Seminar

ABBL/iTHEMS seminar - talk on ultra-high energy cosmic rays

January 31 at 14:00 - 15:00, 2020

Dr. Eiji Kido (Astrophysical Big Bang Laboratory, RIKEN Cluster for Pioneering Research (CPR))

Venue: Seminar Room #132

Event Official Language: English


iTHEMS Math Seminar

Index of the Wilson-Dirac operator revisited: a discrete version of Dirac operator on a finite lattice

February 25 at 16:00 - 18:10, 2020

Dr. Mikio Furuta (Professor, The University of Tokyo)

Venue: Seminar Room #160, 1F Main Research Building, RIKEN

Event Official Language: English

Upcoming Visitor

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January 27 - February 3, 2020

Dr. Jason Chang

Research Scientist, iTHEMS / LBNL/UCB, USA

Research fields: Particle and Nuclear Physics

Visiting Place: #233, 2F, Main Research Building

Person of the Week

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Self-introduction: Martin Skrodzki


My name is Martin Skrodzki and I was born in Germany. I studied computer science and mathematics from 2008 to 2011 at TU Dortmund University in Germany where I obtained two Bachelor's degrees. Afterwards, I spend two terms on a Fulbright travel grant at the Texas A&M International University in Laredo, Texas, USA continuing with graduate studies in mathematics. I finishes these with a Master's degree at Freie Universität Berlin, Germany in 2014. My focus in the coursework and in my Master's thesis was on discrete geometry and discrete mathematics.

In early 2015, I started work on my PhD with Prof. Polthier at Freie Universität Berlin in the group "Mathematical Geometry Processing". My thesis, titled "Neighborhood Data Structures, Manifold Properties, and Processing of Point Set Surfaces" covers three topics all centered in the context of point set processing. Please find the thesis via the link shown below. I graduated with the title of "Dr. rer. nat" (doctor of the natural sciences) in July 2019. Immediately after my graduation, I started a first postdoc at the Institute of Computational and Experimental Research in Mathematics (ICERM), Brown University, Providence, RI, USA. The position was part of the topical semester program "Illustrating Mathematics" which was concerned about finding new, exciting visualizations of mathematical structures and objects, see the link shown below for some of the results obtained.

My research interests are set between computer science and mathematics. I am currently very interested in visualization of high-dimensional data via dimension-reduction methods. Memberships in the Society of Applied and Industrial Mathematics (SIAM), the Solid Modeling Association (SMA), and Eurographics (EG) form my professional network. Finally, I am also an associate editor of the Journal of Mathematics and the Arts (JMA).

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