1,085 research outputs found
Holographic Floquet states II: Floquet condensation of vector mesons in nonequilibrium phase diagram
With the aim to reveal universal features of hadronic matter and correlated
Dirac insulators in strong AC-electric fields, we study the
supersymmetric QCD with a finite quark mass driven by a rotating electric field
. The analysis is done in the
holographically dual D3/D7 system in the co-rotating frame, effectively. The
nonequilibrium phase diagram is determined from the threshold electric field at
which the insulator phase breaks down to a conductive phase due to the AC
version of the Schwinger mechanism. The external field induces a rotating
current originating from
vacuum polarization and dissipative current in the insulating and conductive
phases respectively. Intriguing features are observed as the frequency
approaches resonance with the meson excitation energy .
There, the threshold minimizes and a condensate of vector mesons with
oscillating current exists even in the zero driving field limit. This state,
which we call Floquet condensate of vector mesons, is expected to be
dynamically stable realizing a non-thermal fixed point that breaks time
translational and reversal symmetries. Our finding has many similarities with
exciton BEC discussed in solid state systems, where the semiconductor is to be
replaced by materials hosting gapped Dirac electrons, e.g. 3D topological
insulators or bismuth. Vector meson Floquet condensate may also have
implications in the pre-thermalized dynamics in heavy ion collision
experiments.Comment: 36 pages, 15 figure
Holographic Floquet states: (I) A strongly coupled Weyl semimetal
Floquet states can be realized in quantum systems driven by continuous
time-periodic perturbations. It is known that a state known as the Floquet Weyl
semimetal can be realized when free Dirac fermions are placed in a rotating
electric field. What will happen if strong interaction is introduced to this
system? Will the interaction wash out the characteristic features of Weyl
semimetals such as the Hall response? Is there a steady state and what is its
thermodynamic behavior? We answer these questions using AdS/CFT correspondence
in the supersymmetric massless QCD in a rotating electric field
in the large limit realizing the first example of a "holographic Floquet
state". In this limit, gluons not only mediate interaction, but also act as an
energy reservoir and stabilize the nonequilibrium steady state (NESS). We
obtain the electric current induced by a rotating electric field: In the high
frequency region, the Ohm's law is satisfied, while we recover the DC nonlinear
conductivity at low frequency, which was obtained holographically in a previous
work. The thermodynamic properties of the NESS, e.g., fluctuation-dissipation
relation, is characterized by the effective Hawking temperature that is defined
from the effective horizon giving a holographic meaning to the "periodic
thermodynamic" concept. In addition to the strong (pump) rotating electric
field, we apply an additional weak (probe) electric field in the spirit of the
pump-probe experiments done in condensed matter experiments. Weak DC and AC
probe analysis in the background rotating electric field shows Hall currents as
a linear response, therefore the Hall response of Floquet Weyl semimetals
survives at the strong coupling limit. We also find frequency mixed response
currents, i.e., a heterodyning effect, characteristic to periodically driven
Floquet systems.Comment: 30 pages, 12 figure
Meson turbulence at quark deconfinement from AdS/CFT
Based on the QCD string picture at confining phase, we conjecture that the
deconfinement transition always accompanies a condensation of higher meson
resonances with a power-law behavior, "meson turbulence". We employ the AdS/CFT
correspondence to calculate the meson turbulence for
supersymmetric QCD at large and at strong coupling limit, and find that
the energy distribution to each meson level scales as with the
universal scaling . The universality is checked for various ways to
attain the quark deconfinement: a static electric field below/around the
critical value, a time-dependent electric field quench, and a time-dependent
quark mass quench, all result in the turbulent meson condensation with the
universal power around the deconfinement.Comment: 20 pages, 17 figure
Electric Field Quench in AdS/CFT
An electric field quench, a suddenly applied electric field, can induce
nontrivial dynamics in confining systems which may lead to thermalization as
well as a deconfinement transition. In order to analyze this nonequilibrium
transitions,we use the AdS/CFT correspondence for
supersymmetric QCD that has a confining meson sector. We find that the electric
field quench causes the deconfinement transition even when the magnitude of the
applied electric field is smaller than the critical value for the static case
(which is the QCD Schwinger limit for quark-antiquark pair creation). The time
dependence is crucial for this phenomenon, and the gravity dual explains it as
an oscillation of a D-brane in the bulk AdS spacetime. Interestingly, the
deconfinement time takes only discrete values as a function of the magnitude of
the electric field. We advocate that the new deconfinement phenomenon is
analogous to the exciton Mott transition.Comment: 43 pages, 21 figure
Turbulent meson condensation in quark deconfinement
In a QCD-like strongly coupled gauge theory at large N_c, using the AdS/CFT
correspondence, we find that heavy quark deconfinement is accompanied by a
coherent condensation of higher meson resonances. This is revealed in
non-equilibrium deconfinement transitions triggered by static, as well as,
quenched electric fields even below the Schwinger limit. There, we observe a
"turbulent" energy flow to higher meson modes, which finally results in the
quark deconfinement. Our observation is consistent with seeing deconfinement as
a condensation of long QCD strings.Comment: 5 pages, 5 figure
Forensic voice comparison using sub-band cepstral distances as features: A first attempt with vowels from 306 Japanese speakers under channel mismatch conditions
This study presents the latter part of an exploratory study of the potential of sub-band parametric cepstral distance (PCD) as an alternative forensic voice comparison (FVC) feature to formants and cepstral coefficients. Using 5 Japanese vowels produced by 306 male Japanese speakers, we conducted LRbased FVC experiments under a channel mismatch condition, with sub-bands selected in reference to the expected formant locations. Combining 3 sub-band PCDs from F1, F2, and F3 ranges, sub-band PCDs outperformed the full-band PCDs in speaker classification, demonstrating their promise as an automatically extractable, robust, and linguistically interpretable acoustic feature for FVC. Index Terms: Sub-band cepstral distance, likelihood ratio, forensic voice comparison, channel mismatch, Japanese vowelsThe work presented here was partly supported by JSPS KAKENHI Grant Number JP18H01671, JP25350488
Multiple-system atrophy and anesthesia
Multiple-system atrophy is an adult-onset progressive neurodegenerative disease affecting the central nervous system, including the spinal cord. There has been no perioperative guideline of the muscle relaxants used in multiple-system atrophy, although a recent article recommends anesthesiologists to use shorter-acting drugs at the lowest possible doses in the patients. Here, we document the first case with multiple-system atrophy undergoing surgery managed with a combination of rocuronium and sugammadex. The recovery time to the train-of-four count 2 after intravenous rocuronium 0.6 mg / kg, or the time from the start of sugammadex 2 mg / kg intravenously to the train-of-four ratio over 0.9 was prolonged in our case more than 20 and 2 minutes compared with those in healthy subjects, respectively. Neuromuscular monitoring, in addition to the careful vigilance in the perioperative period, seems mandatory in the patients
Exploring sub-band cepstral distances for more robust speaker classification
This paper presents the first of two-part exploration into the potential of parametric cepstral distance (PCD) as a forensic voice comparison feature, based on Japanese vowel data collected from 306 male native speakers under microphone and mobile transmission conditions. The behaviours of PCDs were closely examined by altering sub-band settings, and we found the behaviour of PCDs to correspond well to what is known about formants, which suggests that PCDs are relatable to articulatory gestures. Comparison between sub-band and full-band PCD revealed that limiting the band range to a specific frequency region makes the feature more robust against channel mismatch, encouraging further examination of this potential feature.The work presented here was partly supported by JSPS KAKENHI Grant Number JP18H01671, JP25350488
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