56 research outputs found
Lock-in transition of charge density waves in quasi-one-dimensional conductors: reinterpretation of McMillan's theory
We investigated the lock-in transition of charge density waves (CDWs) in
quasi-one-dimensional conductors, based on McMillan's free energy. The
higher-order umklapp terms play an essential role in this study. McMillan's
theory was extended by Nakanishi and Shiba in order to treat multiple CDW
vectors. Although their theories were aimed at understanding CDWs in
quasi-two-dimensional conductors, we applied them to the quasi-one-dimensional
conductors, including KMoO, NbSe, and -TaS, and
confirmed its validity for these cases. Then we discussed our previous
experimental result of -TaS, which revealed the coexistence of
commensurate and incommensurate states. We found that the coexistence of
multiple CDW vectors is essential for the lock-in transition to occur in
-TaS. The even- and odd-order terms in the free energy play roles for
amplitude development and phase modulation, respectively. Moreover,
consideration of the condition of being commensurate CDWs allowed us to relate
it with that of the weak localization in random media.Comment: 12 pages, 3 figure
Rotating black hole in extended Chern-Simons modified gravity
We investigate a slowly rotating black hole in four-dimensional extended
Chern-Simons modified gravity. We obtain an approximate solution that reduces
to the Kerr solution when a coupling constant vanishes. The Chern-Simons
correction effectively reduces the frame-dragging effect around a black hole in
comparison with that of the Kerr solution.Comment: 9 pages, 1 figure, to appear in Progress of Theoretical Physics,
typos correcte
Direct Observation of Mono-, Bi-, and Tri-layer Charge Density Waves in 1T-TaS_2 by Transmission Electron Microscopy without a Substrate
Charge-density-waves (CDW) which occur mainly in low-dimensional systems have
a macroscopic wave function similar to superfluids and superconductors.
Kosterlitz-Thouless (KT) transition is observed in superfluids and
superconductors, but the presence of KT transition in ultra-thin CDW systems
has been an open problem. We report the direct real-space observation of CDWs
with new order states in mono-, bi-, and tri-layer 1T-TaS_2 crystal by using a
low voltage scanning-transmission-electron-microscope (STEM) without a
substrate. This method is ideal to observe local atomic structures and possible
defects. We clearly observed that the mono-layer crystal has a new triclinic
stripe CDW order without the triple q condition q_1 + q_2 + q_3 = 0. A strong
electron-phonon interaction gives rise to new crevasse (line) type defects
instead of disclination (point) type defects due to the KT transition. These
results reaffirm the importance of the electron-phonon interaction in
mono-layer nanophysics.Comment: 5 figures, 1 tabl
Does a black hole rotate in Chern-Simons modified gravity?
Rotating black hole solutions in the (3+1)-dimensional Chern-Simons modified
gravity theory are discussed by taking account of perturbation around the
Schwarzschild solution. The zenith-angle dependence of a metric function
related to the frame-dragging effect is determined from a constraint equation
independently of a choice of the embedding coordinate. We find that at least
within the framework of the first-order perturbation method, the black hole
cannot rotate for finite black hole mass if the embedding coordinate is taken
to be a timelike vector. However, the rotation can be permitted in the limit of
(where is the black hole mass and is the radius). For a
spacelike vector, the rotation can also be permitted for any value of the black
hole mass.Comment: 4 pages, Accepted for publication in Phys. Rev.
Detect Kernel-Mode Rootkits via Real Time Logging & Controlling Memory Access
Modern malware and spyware platforms attack existing antivirus solutions and even Microsoft PatchGuard. To protect users and business systems new technologies developed by Intel and AMD CPUs may be applied. To deal with the new malware we propose monitoring and controlling access to the memory in real time using Intel VT-x with EPT. We have checked this concept by developing MemoryMonRWX, which is a bare-metal hypervisor. MemoryMonRWX is able to track and trap all types of memory access: read, write, and execute. MemoryMonRWX also has the following competitive advantages: fine-grained analysis, support of multi-core CPUs and 64-bit Windows 10. MemoryMonRWX is able to protect critical kernel memory areas even when PatchGuard has been disabled by malware. Its main innovative features are as follows: guaranteed interception of every memory access, resilience, and low performance degradation
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