arXiv subjects

Masahiro Morikawa

Publications and source records attributed to Masahiro Morikawa.

At least 19 recordsLinked to original sources

arXiv2026

Infrared Divergences as Itinerant Vacua

Infrared divergences (IRDs) are usually treated as pathologies to be cancelled, regularized, or hidden in dressed asymptotic states. This paper develops a complementary and constructive viewpoint: an IRD is the signature of an \emph{itinerant vacuum} -- a quantum vacuum that wanders continuously through a family of inequivalent states as a classical order parameter evolves. Each value of the order parameter carries its own coherent vacuum, so moving the order parameter means traversing a succession of orthogonal vacua. The IRD is the field-theoretic cost of this wandering, and the $1/f$ noise, gravitational memory, and non-Gaussian fluctuations that emerge from it are its observable classical remnants. The technical core is an exact separation in the real-time closed-time-path (CTP) effective action. The infrared-divergent imaginary part of the influence functional must not be left as a divergent coefficient in a deterministic equation of motion; it is instead converted, by a Hubbard--Stratonovich identity, into a classical stochastic source. This step is an algebraic identity of the generating functional and requires no prior coarse graining or decoherence assumption: the retarded kernel encodes the memory of past vacuum transitions, while the noise kernel encodes the quantum uncertainty of the next one. We apply this construction to four parallel arenas -- soft QED, scalar fields in de Sitter space, soft gravitons, and non-equilibrium phase transitions -- and show that the same itinerant-vacuum mechanism underlies $1/f$ current noise, the primordial power spectrum, gravitational memory, and order-parameter dynamics. A geometric formulation in terms of a Hilbert-space bundle over the vacuum manifold is outlined as an outlook.

hep-th↗

arXiv2026

Pink Noise in Economic Time Series from Synchronization and Amplitude Demodulation

Pink noise, characterized by a power spectral density $S(ω)\proptoω^β$ with $β\simeq -1$, appears in economic indices as well as in many natural systems. We summarize a unified mesoscopic interpretation in which pink spectra arise from repeated synchronization, amplitude modulation, and demodulation. In economic time series, we identify two kinds of pink-noise behavior: one that appears in the raw data (property A), and another that appears only after detrending and demodulation (property B). A stochastic Kuramoto model provides a minimal dynamical model of repeated synchronization and desynchronization among many economic circulations. It produces approximate $1/f$ spectra over a broad coupling--system-size domain and gives variance--mean scaling, Taylor's law. The same amplitude-modulation/demodulation mechanism also gives a compact explanation of pink spectra in music, earthquakes, variable stars, solar flares, and black-hole accretion systems. Pink noise is therefore interpreted not merely as a statistical regularity, but as a diagnostic of slowly modulated collective coherence in complex flow systems.

nlin.AO↗

arXiv2026

A Synchronized Spin Model for Black-Hole Accretion Systems

Black-hole accretion systems exhibit a characteristic coexistence of activities: broad-band X-ray variability, hot coronae, wide-angle winds, and both steady and discrete jets. This coexistence suggests a persistently time-dependent magnetic background in which noisy fluctuations and explosive release are both essential. In this paper, we connect them all to intermittent magnetic reconnection and propose a Synchronized Spin Model (SSM) in which multiple local dynamos in a rotating accretion flow are represented as interacting macro-spins. Their synchronization, partial synchronization, excursion, and reversal define a compact set of collective variables that organize both timing statistics and large-scale morphology. In this picture, multiscale magnetic reconnection sustains coronal heating, flares, intermittent outflows, and discrete jet activity, while the same synchronization dynamics produce amplitude modulation and demodulation, providing a route to $1/f$-like variability, rms--flux/Taylor-like scaling, and approximately log-normal statistics of the demodulated envelope. We further argue that, although the continuous flux distribution in black-hole systems is more naturally discussed in multiplicative or log-normal terms, broader event-catalog statistics remain useful for describing suitably defined burst hierarchies, particularly by analogy with solar and stellar flare systems. The hard/soft cycle of X-ray binaries is then interpreted as motion through magnetic state space.

astro-ph.HE↗

arXiv2025

Pink noise in Electric Current from Amplitude Modulations

We recently proposed that the general origin of 1/f fluctuation, or pink noise, is the amplitude modulation (or beat) of many waves with accumulating frequencies. In this paper, we verify this proposal in the electric current system. We use the classical Langevin equation to describe the electron wave packets flowing in the (semi-)conductor, affected by the back reaction of soft photon emission. If this were amplitude modulation, a demodulation process is needed to extract the fluctuation features. We first square the wave packet, which corresponds to the electric current, and obtain the 1/f fluctuation in this current data. We further speculate that this wave packet, after demodulation by thresholding, triggers the time sequence of the nerve firing. In our model, this also shows 1/f fluctuations, which is quite robust.

cond-mat.stat-mech↗

arXiv2025

Dynamic Synchronization and Resonance as a Universal Origin of 1/f Fluctuations -- Amplitude Modulation Across Music and Nature

We propose a universal physical mechanism for the emergence of 1/f fluctuations, observed across a wide range of systems. In particular, we verify this on acoustic cases. The mechanism is based on amplitude modulation (AM) and demodulation (DM), where the 1/f spectral law arises not in the raw waveform but in its demodulated amplitude envelope. Two distinct yet complementary processes generate the required AM: (i) stochastic synchronization among oscillators, modeled via an extended Kuramoto framework that captures perpetual synchronization-desynchronization cycles, and (ii) frequency-selective resonance, modeled by spectral accumulation of eigenmodes in acoustic or structural environments. Numerical simulations demonstrate that both mechanisms, acting separately or in combination, robustly produce 1/f spectra over several decades when DM is applied, and that the classical Kuramoto critical point is not necessary for their emergence. We demonstrate the cross-domain relevance of this AM/DM framework through analyses of musical performances, seismic records, and astrophysical time series, revealing a common underlying structure. This work establishes demodulation as a general route to 1/f fluctuations, providing a simple and scalable explanation for its ubiquity in both natural and engineered systems. Keywords: 1/f fluctuation, amplitude modulation, synchronization, resonance, Kuramoto model, music, natural noise, demodulation

cs.SD↗

arXiv2023

Seismic 1/f Fluctuations from Amplitude Modulated Earth's Free Oscillation

We first report that the seismic time-sequence data from around the world, excluding major earthquakes, consistently yield the power spectral density inversely proportional to the frequency f. This is the 1/f fluctuation that appears ubiquitously in nature. We investigate the origin of this 1/f fluctuation based on our recent proposal: 1/f noise is amplitude modulation and demodulation. We hypothesize that the amplitude modulation is linked to resonance with Earth's Free Oscillations (EFO), with demodulation occurring during fault ruptures. We provide partial validation of this hypothesis through an analysis of EFO eigenmodes. Additionally, we outline potential methods for the future verification of our theory relating 1/f fluctuations to EFO.

physics.geo-ph↗

arXiv2023

Solar Flare 1/f Fluctuations from Amplitude Modulated Five Minute Oscillation

We first study the solar flare time sequence based on the GOES16 data. We find that the power spectrum density of the low-energy (E\leq E_{mean}) flare shows 1/f fluctuations, but the high-energy (E>E_{mean}) flare shows a flat spectrum. Further, we found that the flare timing time-sequence shows 1/f fluctuations clearer. These facts indicate that the solar flare 1/f fluctuations are associated with low-energy phenomena. We investigate the origin of this 1/f fluctuations based on our recent proposal: 1/f fluctuations arise from amplitude modulation and demodulation. We speculate that this amplitude modulation is encoded by the resonance with the Solar Five-minute Oscillation (SFO) and demodulated by magnetic reconnection. We partially demonstrate this scenario by analyzing the SFO eigenmodes resolving the frequency degeneracy in the azimuthal order number m by solar rotation and resonance. Since 1/f fluctuation is robust, we speculate that the solar flare 1/f fluctuations may be inherited by the various phenomena around the Sun, such as the sunspot numbers and the cosmic rays. Finally, we compare the solar flares and the earthquakes, both showing 1/f fluctuations. Interestingly, the same analysis for solar flares is possible for earthquakes if we read SFO as Earth's Free Oscillation, and magnetic reconnection as fault rupture. Furthermore, we point out the possibility that the same analysis also applies to the activity of the black hole/disk system if we read SFO as the Quasi-Periodic Oscillation of a black hole.

astro-ph.SR↗

arXiv2023

A simple model for pink noise from amplitude modulations

We propose a simple model for the origin of pink noise (or 1/f fluctuation) based on the beat of cooperative waves. These cooperative waves arise spontaneously in a system with synchronization, resonance, and infrared divergence. Many cooperative waves with close frequencies can produce signals of arbitrary small frequencies from a system of small size. This beat mechanism can be understood as amplitude modulation. The pink noise can appear after the demodulation process, which produces a variety of pink noise in many fields. The pink noise thus formed from the beat has nothing to do with dissipation or long-time memory. We also suggest new ways of looking at pink noise in shallow earthquakes, solar flares, and stellar activities.

eess.AS↗

arXiv2021

Supermassive Black Holes from Bose-Einstein Condensed Dark Matter -- or Black and Dark Separation by Angular Momentum

Many supermassive black holes (SMBH) of mass $10^{6\sim9}M_{\odot}$ are observed at the center of each galaxy even in the high redshift ($z\approx7$) Universe. To explain the early formation and the common existence of SMBH, we proposed previously the SMBH formation scenario by the gravitational collapse of the coherent dark matter (DM) composed from the Bose-Einstein Condensed (BEC) objects. A difficult problem in this scenario is the inevitable angular momentum which prevents the collapse of BEC. To overcome this difficulty, in this paper, we consider the very early Universe when the BEC-DM acquires its proper angular momentum by the tidal torque mechanism. The balance of the density evolution and the acquisition of the angular momentum determines the mass of the SMBH as well as the mass ratio of BH and the surrounding dark halo (DH). This ratio turns out to be $M_{BH}/M_{DH}\approx10^{-3\sim-5}(M_{tot}/10^{12}\mathrm{M}_{\odot})^{-1/2}$ assuming simple density profiles of the initial DM cloud. This estimate turns out to be consistent with the observations at $z\approx0$ and $z\approx6$, although the data scatter is large. Thus the angular momentum determines the separation of black and dark, \textsl{i.e. }SMBH and DH, in the original DM cloud.

astro-ph.GA↗

arXiv2021

Low-Frequency Characterization of Music Sounds -- Ultra-Bass Richness from the Sound Wave Beats

The orchestra performance is full of sublime rich sounds. In particular, the unison of violins sounds different from the solo violin. We try to clarify this difference and similarity of unison and solo numerically analyzing the beat of `violins` with timbre, vibrato, melody, and resonance. Characteristic properties appear in the very low-frequency part in the power spectrum of the wave amplitude squared. This ultra-buss richness (UBR) can be a new characteristic of sound on top of the well-known pitch, loudness, and timbre, although being inaudible directly. We find this UBR is always characterized by a power-law at low-frequency with the index around -1 and appears everywhere in music and thus being universal. Furthermore, we explore this power-law property towards much smaller frequency regions and suggest possible relation to the 1/f noise often found in music and many other fields in nature.

cs.SD↗

arXiv2020

Planetary System from the Outer Edge of the Inner Void -- Classes and Populations of Variety

Planets are common objects in the Universe, observationally as well as theoretically. However, the standard theory of their formation encounters many difficulties, such as dust fall and disk lifetime problems. We positively analyze them, expecting that those problems as a whole may indicate some consistent effective model. Thus we propose a dynamical model of the planet formation based on the assumption that the inner void of gas is commonly formed in the disk without specifying any Physical origin. The basic processes of this model are the dust fall, the accumulation, and the slingshots. The dust in the protoplanetary disk rapidly falls as it grows to the meter size. Then, all of them stops at the outer edge of the void where the gas friction disappears. Such dust clusters rapidly coalesce with each other and easily cause the runaway in the dense and coherent environment. Then the huge clusters are formed there and they are the first generation planets Hot-Jupiters. They immediately slingshot smaller clusters around them towards the outer regions. They are Rockey-Planets, Cold-Gas-Giants, Ice-Giants, and `Trans Neptunian objects including `Kuiper belt/Oort cloud objects`, depending on the original core mass or the distance blown. Combining numerical calculations of the slingshots and coagulation equations, we obtain the planet population diagram, including the possibility of the massive thermal metamorphosis, the origin of the variety of planetary systems, and the possibility of stray planets/objects.

astro-ph.EP↗

arXiv2018

Transient Dynamics from Quantum to Classical- From the Developed Coherent State via Extreme Squeezing -

We explore the transient dynamics associated with the emergence of the classical signal in the full quantum system. We start our study from the instability which promotes the squeezing of the quantum system. This is often interpreted as the particle production though being reversible in time. We associate this state a non-dissipative classical fluctuations and study their trigger to develop the coherent state which can be classical if sufficiently developed. The Schwinger-Keldysh in-in formalism yields the classical Langevin equation including the fluctuation force which faithfully reflects the particle production property of the original quantum system. This formalism is applied to some transient process; the initiation of the spontaneous symmetry breaking, appearance of the off-diagonal long-range order in Bose-Einstein condensation, a transient process of the classicalization of the quantum fluctuations in the inflationary cosmology,... and gives some implications on the origin of the irreversibility associated with the transition from quantum to classical.

quant-ph↗

arXiv2017

Spontaneous Super-Rotation on Planets

Super-rotations of the planetary atmosphere are reconsidered from the dynamical point of view. In particular, we emphasize that the super-rotation appears spontaneously without any explicit force. Although the super-rotation violates the bilateral symmetry (east-west reflection symmetry) of the system, this violation is spontaneous. Constructing a minimal model that derives the super-rotation, we clarify the condition for the super-rotation to appear. We find that the flow is always determined autonomously so that the flow speed becomes maximum or the temperature difference smallest. After constraining the parameters of the model from observations, we compare our model with the others most of which demand the explicit symmetry violation due to the planetary rotation.

astro-ph.EP↗

arXiv2016

Infrared Divergence Separated for Stochastic Force - Langevin Evolution in the Inflationary Era

Inflation in the early Universe is a grand phase transition which have produced the seeds of all the structures we now observe. We focus on the non-equilibrium aspect of this phase transition especially the inevitable infrared (IR) divergence associated to the the quantum and classical fields during the inflation. There is a long history of research for removing this IR divergence for healthy perturbation calculations. On the other hand, the same IR divergence is quite relevant and have developed the primordial density fluctuations in the early Universe. We develop a unified formalism in which the IR divergence is clearly separated from the microscopic quantum field theory but only appear in the statistical classical structure. We derive the classical Langevin equation for the order parameter within the quantum field theory through the instability of the de Sitter vacuum during the inflation. This separation process is relevant in general to develop macroscopic structures and to derive the basic properties of statistical mechanics in the quantum field theory.

hep-th↗

arXiv2016

Galaxies nurtured by mature black holes

Supermassive black holes (SMBH) of size $10^{6-10}M_{\odot}$ are common in the Universe and they define the center of the galaxies. A galaxy and the SMBH are generally thought to have co-evolved. However, the SMBH cannot evolve so fast as commonly observed even at redshift $z>6$. Therefore SMBH must form first before galaxy. Our goal is to clarify how this mature SMBH forms galaxy. Furthermore we clarify the mechanism how the SMBH designs variety of structures of galaxies. We explore a natural hypothesis that the SMBH has been formed mature at $z\approx10$ before stars and galaxies. The SMBH forms energetic jets and outflows which trigger massive star formation in the ambient gas. They eventually construct globular clusters and classical bulge as well as the body of elliptical galaxies. We propose simple models which implement these processes along with the standard $Λ$CDM-model. We point out that the globular clusters and classical bulges have a common origin but are in different phases. The same is true for the elliptical and spiral galaxies. Physics behind these phase division is the runaway star formation process with strong feedback to SMBH. This is similar to the forest-fire model that displays self-organized criticality. Finally we speculate several observational predictions that may help to test the present arguments.

astro-ph.GA↗

arXiv2014

Physics of quantum measurement and its interdisciplinary applications

Quantum dynamics of the collective mode and individual particles on a ring is studied as the simplest model of projective quantum measurement. In this model, the collective mode measures an individual single quantum system. The heart of the model is the wide separation of time scales which yields the distinction of classical and quantum degrees of freedom beyond the standard Gross-Pitaevskii equation. In some restricted cases we derive the Born probability rule. This model is the quantum mechanics version of the effective action method in quantum field theory, which describes the origin of the primordial density fluctuation as classical variables. It turns out that the classical version of this same model successfully describes the dynamics of geomagnetic variation including the polarity flips over 160 million years. The essence of this description is again the coexistence of the wide separated time scales.

quant-ph↗

arXiv2012

EPR measurement and the origin of cosmic density fluctuations

We explore consistent application of quantum mechanics to the objects in the Universe and in laboratories. The measurement dynamics in quantum mechanics is modeled as a physical process of spontaneous symmetry breaking (SSB) which is described by the generalized effective action method. A violation of the Bell inequality is observed in this model and the generation of the density fluctuations in the early Universe is described as the SSB process of the spatially translational symmetry.

quant-ph↗

arXiv2009

Scaling Relations for Collision-less Dark Matter Turbulence

Many scaling relations are observed for self-gravitating systems in the universe. We explore the consistent understanding of them from a simple principle based on the proposal that the collision-less dark matter fluid terns into a turbulent state, i.e. dark turbulence, after crossing the caustic surface in the non-linear stage. The dark turbulence will not eddy dominant reflecting the collision-less property. After deriving Kolmogorov scaling laws from Navier-Stokes equation by the method similar to the one for Smoluchowski coagulation equation, we apply this to several observations such as the scale-dependent velocity dispersion, mass-luminosity ratio, magnetic fields, and mass-angular momentum relation, power spectrum of density fluctuations. They all point the concordant value for the constant energy flow per mass: $0.3 cm^2/sec^3$, which may be understood as the speed of the hierarchical coalescence process in the cosmic structure formation.

astro-ph↗