Yuki Sato

Electronic state of every solid is basically classified into two categories according to its electrical responses: insulator or metal. A textbook of modern solid state physics explains that shape of a Fermi surface plays a key role in most physical properties in metals. One of the well-established experimental methods to detect a Fermi surface is measurement of quantum oscillations that is a periodic response of physical quantities with respect to external magnetic fields. As insulators do not host Fermi surface, it is believed that they do not exhibit any quantum oscillations. This book presents a comprehensive review of recent observations of quantum oscillations in the Kondo insulators, SmB6 and YbB12, and discusses how the observations are demonstrated by a newly proposed mechanism where emergent charge-neutral fermions exhibit quantum oscillations instead of bare electrons. It also focuses on topological properties of Kondo insulators, and demonstrates that YbB12 hosts asurface metallic conduction owing to its non-trivial band structure. Further it presents the experiments of specific heat and thermal conductivity in YbB12 down to ultra-low temperature to discuss the possible low-energy excitations from a Fermi surface of neutral fermions. The demonstrated gapless and itinerant fermionic excitations, that is the significant contribution from charge neutral fermions, violates Wiedemann-Franz law. The discoveries point out a highly unconventional phase of quantum state—electrically insulating but thermally metallic—realized in the bulk of topological Kondo insulators.

Electronic state of every solid is basically classified into two categories according to its electrical responses: insulator or metal. A textbook of modern solid state physics explains that shape of a Fermi surface plays a key role in most physical properties in metals. One of the well-established experimental methods to detect a Fermi surface is measurement of quantum oscillations that is a periodic response of physical quantities with respect to external magnetic fields. As insulators do not host Fermi surface, it is believed that they do not exhibit any quantum oscillations. This book presents a comprehensive review of recent observations of quantum oscillations in the Kondo insulators, SmB6 and YbB12, and discusses how the observations are demonstrated by a newly proposed mechanism where emergent charge-neutral fermions exhibit quantum oscillations instead of bare electrons. It also focuses on topological properties of Kondo insulators, and demonstrates that YbB12 hosts asurface metallic conduction owing to its non-trivial band structure. Further it presents the experiments of specific heat and thermal conductivity in YbB12 down to ultra-low temperature to discuss the possible low-energy excitations from a Fermi surface of neutral fermions. The demonstrated gapless and itinerant fermionic excitations, that is the significant contribution from charge neutral fermions, violates Wiedemann-Franz law. The discoveries point out a highly unconventional phase of quantum state—electrically insulating but thermally metallic—realized in the bulk of topological Kondo insulators.

In this thesis, the author considers quantum gravity to investigate the mysterious origin of our universe and its mechanisms. He and his collaborators have greatly improved the analyticity of two models: causal dynamical triangulations (CDT) and n-DBI gravity, with the space-time foliation which is one common factor shared by these two separate models. In the first part, the analytic method of coupling matters to CDT in 2-dimensional toy models is proposed to uncover the underlying mechanisms of the universe and to remove ambiguities remaining in CDT. As a result, the wave function of the 2-dimensional universe where matters are coupled is derived. The behavior of the wave function reveals that the Hausdorff dimension can be changed when the matter is non-unitary. In the second part, the n-DBI gravity model is considered. The author mainly investigates two effects driven by the space-time foliation: the appearance of a new conserved charge in black holes and an extra scalar mode of the graviton. The former implies a breakdown of the black-hole uniqueness theorem while the latter does not show any pathological behavior.

In this thesis, the author considers quantum gravity to investigate the mysterious origin of our universe and its mechanisms. He and his collaborators have greatly improved the analyticity of two models: causal dynamical triangulations (CDT) and n-DBI gravity, with the space-time foliation which is one common factor shared by these two separate models. In the first part, the analytic method of coupling matters to CDT in 2-dimensional toy models is proposed to uncover the underlying mechanisms of the universe and to remove ambiguities remaining in CDT. As a result, the wave function of the 2-dimensional universe where matters are coupled is derived. The behavior of the wave function reveals that the Hausdorff dimension can be changed when the matter is non-unitary. In the second part, the n-DBI gravity model is considered. The author mainly investigates two effects driven by the space-time foliation: the appearance of a new conserved charge in black holes and an extra scalar mode of the graviton. The former implies a breakdown of the black-hole uniqueness theorem while the latter does not show any pathological behavior.

Takeru loves dogs, so he heads to the pound to adopt one. When he gets there, he notices a dog who doesn't play or interact with the other dogs - and he brings the dog home. Then he starts to hear voices... But he's not crazy. It's just that the legendary detective Sherlock Holmes has been reincarnated in the body of this small pup, and only Takeru can hear his human voice! Taking on the role of Watson, Takeru and Holmes (a.k.a., Sherlock Bones) work to solve crimes across modern day Tokyo!

Karvainen mestarietsivä vauhdissa! Takeru ja Sherdock ovat asiakkaansa murhanneen plastiikkakirurgin kintereillä. Etsivä Munakata alkaa kummastella Takerun tapaa ottaa Sherdock mukaan rikospaikoille ja tämä taantuu tavalliseksi koiraksi. Onko etsiväkaksikkomme taru lopussa ja ehtiikö paha saada palkkansa? Ikäsuositus: 12+

Takeru loves dogs, so he heads to the pound to adopt one. When he gets there, he notices a dog who doesn't play or interact with the other dogs - and he brings the dog home. Then he starts to hear voices... But he's not crazy. It's just that the legendary detective Sherlock Holmes has been reincarnated in the body of this small pup, and only Takeru can hear his human voice! Taking on the role of Watson, Takeru and Holmes (aka, Sherlock Bones) work to solve crimes across modern day Tokyo!

Karvainen mestarietsivä vauhdissa! Sherdock ja Takeru jatkavat rikosten ratkomista. Tuskin on neito ehditty pelastaa pulasta, kun on aika napata lompakkovaras käpälälautaan. Myös Sherlock Holmesin arkkivihollinen James Moriarty tassuttelee mukaan kuvioihin! Ikäsuositus: 12+

Karvainen mestarietsivä vauhdissa! Kuvankaunis pormestari murhaa entisen rakastajansa ja peittelee jälkensä huolellisesti... Paikalle sattuneet Sherdock ja Takeru ovat jälleen valmiita laittamaan syyllisen ahtaalle, mutta saako pormestari etsiväkaksikosta sen sijaan täydellisen alibin itselleen? Luvassa on kihelmöivää jännitystä ja hersyvää huumoria! Ikäsuositus: 12+

Karvainen mestarietsivä vauhdissa! Takeru luuli saavansa suloisesta koiranpennusta mukavan lemmikin, mutta Sherdock onkin jotain aivan muuta... Lehteä lukeva ja piippua poltteleva etsiväkoira aiheuttaa Takerun äidille harmaita hiuksia, mutta suurempi järkytys on varattuna kauniin näyttelijättären murhanneelle konnalle, sillä rikoksen silminnäkijäksi sattuu kukas muu kuin Sherdock. Ikäsuositus: 12+

Karvainen mestarietsivä vauhdissa! Takeru pelastaa koiratarhasta pennun, joka saa nimekseen Sherdock. Sherlock Holmesiin viittaava nimi osoittautuu pian osuvaksi, sillä pennulla on uskomaton vainu rikosten ratkomisen suhteen. Eikä siinä kaikki! Pian Takeru huomaa joutuneensa Watsoniksi Watsonin paikalle... Ikäsuositus: 12+