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Tatsuru Kikuchi

Publications and source records attributed to Tatsuru Kikuchi.

At least 37 records · Page 2Linked to original sources

Gender Similarities Dominate Mathematical Cognition at the Neural Level: A Japanese fMRI Study Using Advanced Wavelet Analysis and Generative AI

Recent large scale behavioral studies suggest early emergence of gender differences in mathematical performance within months of school entry. However, these findings lack direct neural evidence and are constrained by cultural contexts. We conducted functional magnetic resonance imaging (fMRI) during mathematical tasks in Japanese participants (N = 156), employing an advanced wavelet time frequency analysis to examine dynamic brain processes rather than static activation patterns. Wavelet decomposition across four frequency bands (0.01-0.25 Hz) revealed that neural processing mechanisms underlying mathematical cognition are fundamentally similar between genders. Time frequency analysis demonstrated 89.1% similarity in dynamic activation patterns (p = 0.734, d = 0.05), with identical temporal sequences and frequency profiles during mathematical processing. Individual variation in neural dynamics exceeded group differences by 3.2:1 (p $<$ 0.001). Machine learning classifiers achieved only 53.8% accuracy in distinguishing gender based neural patterns essentially at chance level even when analyzing sophisticated temporal spectral features. Cross frequency coupling analysis revealed similar network coordination patterns between genders, indicating shared fundamental cognitive architecture. These findings provide robust process level neural evidence that gender similarities dominate mathematical cognition, particularly in early developmental stages, challenging recent claims of inherent differences and demonstrating that dynamic brain analysis reveals neural mechanisms that static behavioral assessments cannot access.

q-bio.NC↗

Wavelet Analysis of Cryptocurrencies -- Non-Linear Dynamics in High Frequency Domains

In this study, we perform some analysis for the probability distributions in the space of frequency and time variables. However, in the domain of high frequencies, it behaves in such a way as the highly non-linear dynamics. The wavelet analysis is a powerful tool to perform such analysis in order to search for the characteristics of frequency variations over time for the prices of major cryptocurrencies. In fact, the wavelet analysis is found to be quite useful as it examine the validity of the efficient market hypothesis in the weak form, especially for the presence of the cyclical persistence at different frequencies. If we could find some cyclical persistence at different frequencies, that means that there exist some intrinsic causal relationship for some given investment horizons defined by some chosen sampling scales. This is one of the characteristic results of the wavelet analysis in the time-frequency domains.

q-fin.GN↗

Towards A Post-Quantum Cryptography in Blockchain I: Basic Review on Theoretical Cryptography and Quantum Information Theory

Recently, the invention of quantum computers was so revolutionary that they bring transformative challenges in a variety of fields, especially for the traditional cryptographic blockchain, and it may become a real thread for most of the cryptocurrencies in the market. That is, it becomes inevitable to consider to implement a post-quantum cryptography, which is also referred to as quantum-resistant cryptography, for attaining quantum resistance in blockchains.

cs.CR↗

Impact Evaluation on the European Privacy Laws governing generative-AI models -- Evidence in Relation between Internet Censorship and the Ban of ChatGPT in Italy

We proceed an impact evaluation on the European Privacy Laws governing generative-AI models, especially, focusing on the effects of the Ban of ChatGPT in Italy. We investigate on the causal relationship between Internet Censorship Data and the Ban of ChatGPT in Italy during the period from March 27, 2023 to April 11, 2023. We analyze the relation based on the hidden Markov model with Poisson emissions. We find out that the HTTP Invalid Requests, which decreased during those period, can be explained with seven-state model. Our findings shows the apparent inability for the users in the internet accesses as a result of EU regulations on the generative-AI.

econ.GN↗

Methods of Stochastic Field Theory in Non-Equilibrium Systems -- Spontaneous Symmetry Breaking of Ergodicity

Recently, a couple of investigations related to symmetry breaking phenomena, 'spontaneous stochasticity' and 'ergodicity breaking' have led to significant impacts in a variety of fields related to the stochastic processes such as economics and finance. We investigate on the origins and effects of those original symmetries in the action from the mathematical and the effective field theory points of view. It is naturally expected that whenever the system respects any symmetry, it would be spontaneously broken once the system falls into a vacuum state which minimizes an effective action of the dynamical system.

physics.soc-ph↗

Price Stability of Cryptocurrencies as a Medium of Exchange

We present positive evidence of price stability of cryptocurrencies as a medium of exchange. For the sample years from 2016 to 2020, the prices of major cryptocurrencies are found to be stable, relative to major financial assets. Specifically, after filtering out the less-than-one-month cycles, we investigate the daily returns in US dollars of the major cryptocurrencies (i.e., Bitcoin, Ethereum, and Ripple) as well as their comparators (i.e., major legal tenders, the Euro and Japanese yen, and the major stock indexes, S&P 500 and MSCI World Index). We examine the stability of the filtered daily returns using three different measures. First, the Pearson correlations increased in later years in our sample. Second, based on the dynamic time-warping method that allows lags and leads in relations, the similarities in the daily returns of cryptocurrencies with their comparators have been present even since 2016. Third, we check whether the cumulative sum of errors to predict cryptocurrency prices, assuming stable relations with comparators' daily returns, does not exceeds the bounds implied by the Black-Scholes model. This test, in other words, does not reject the efficient market hypothesis.

econ.GN↗

Bosonic Seesaw in the Unparticle Physics

Recently, conceptually new physics beyond the Standard Model has been proposed by Georgi, where a new physics sector becomes conformal and provides "unparticle" which couples to the Standard Model sector through higher dimensional operators in low energy effective theory. Among several possibilities, we focus on operators involving the (scalar) unparticle, Higgs and the gauge bosons. Once the Higgs develops the vacuum expectation value (VEV), the conformal symmetry is broken and as a result, the mixing between the unparticle and the Higgs boson emerges. In this paper, we consider a natural realization of bosonic seesaw in the context of unparticle physics. In this framework, the negative mass squared or the electroweak symmetry breaking vacuum is achieved as a result of mass matrix diagonalization. In the diagonalization process, it is important to have zero value in the (1,1)-element of the mass matrix. In fact, the conformal invariance in the hidden sector can actually assure the zero of that element. So, the bosonic seesaw mechanism for the electroweak symmetry breaking can naturally be understood in the framework of unparticle physics.

hep-ph↗

A solution to the little hierarchy problem in a partly N=2 extension of the MSSM

We extend a model of the Dirac gauginos, which originate from N=2 supersymmetry (SUSY) for the gauge sector, such that the N=2 SUSY is imposed also to the sfermion sector but only for the 3rd generation squarks and sleptons. In addition to the N=2 supersymmetry, our model is constructed based on the SU(3)c times SU(3)L times U(1)' gauge symmetry. By this extension, the dominant source of radiative correction to the Higgs mass squared coming from the stop loop becomes controllable based on the enhanced symmetry. Then it becomes a viable model which provides a solution to the little hierarchy problem in SUSY models. Even in the original scenario, the Dirac gauginos can be superheavy, of order 10 TeV or so, while keeping the scalar masses at the weak scale. This possibility is phenomenologically interesting because it can suppress the unwanted flavor changing processes. And in scope of the LHC, this scenario can have a very distinct signature related to the exotic sfermions which are accompanied as the N=2 superpartners as well as the Dirac gauginos.

hep-ph↗

Enhanced production of TeV right-handed neutrinos through the large magnetic moment

We examine the effects of magnetic moments of right-handed neutrinos, whose masses are set at around TeV scale, then it is plausible to have a large enhancement for the production cross section of TeV scale right-handed neutrinos though the Drell-Yan process, e^+ e^- to gamma, Z* to N_i N_j, which is within the reach of the future linear collider (ILC).

hep-ph↗

B-L assisted Anomaly Mediation and the radiative B-L symmetry breaking

Anomaly mediated supersymmetry breaking implemented in the minimal supersymmetric standard model (MSSM) is known to suffer from the tachyonic slepton problem leading to breakdown of electric charge conservation. We show however that when MSSM is extended to explain small neutrino masses by gauging the B-L symmetry, the slepton masses can be positive due to the Z' mediation contributions. We obtain various soft supersymmetry breaking mass spectra, which are different from those obtained in the conventional anomaly mediation scenario. Then there would be a distinct signature of this scenario at the LHC.

hep-ph↗

B-L mediated SUSY breaking with radiative B-L symmetry breaking

We explore a mechanism of radiative B-L symmetry breaking in analogous to the radiative electroweak symmetry breaking. The breaking scale of B-L symmetry is related to the neutrino masses through the see-saw mechanism. Once we incorporate the U(1)(B-L) gauge symmetry in SUSY models, the U(1)(B-L) gaugino appears, and it can mediate the SUSY breaking (Z-prime mediated SUSY breaking) at around the scale of 10^6 GeV. Then we find a links between the neutrino mass (more precisly the see-saw or B-L scale of order 10^6 GeV) and the Z-prime mediated SUSY breaking scale. It is also very interesting that the gluino at the weak scale becomes relatively light, and almost compressed mass spectra for the gaugino sector can be realized in this scenario, which is very interesting in scope of the LHC.

hep-ph↗

Leptogenesis in a perturbative SO(10) model

We consider a phenomenologically viable SO(10) grand unification model which allows perturbative calculations up to the Planck scale or the string scale. We use a set of Higgs superfields {10 + 16bar + 16 + 45}. In this framework, the data fitting of the charged fermion mass matrices is re-examined. This model can indeed reproduce the low-energy experimental data relating the charged fermion masses and mixings. As for the neutrino sector, we take the neutrino oscillation data as input data to construct right-handed Majorana neutrino mass matrix and get a prediction for the physics related to the right-handed neutrinos, e.g. the leptogenesis and for the proton decay. We propose two kinds of phenomenologically viable model, quoted as Model 1 and Model 2. We show that one of the models (Model 2) is consistent with all experimental constraints.

hep-ph↗

D-term assisted Anomaly Mediation in E6 motivated models

We investigate effects of D-term contributions to the anomaly mediated supersymmetry breaking scenario. If we introduce an E6 GUT motivated D-term, it is possible that slepton mass squared is positive at weak scale even if there are no other D-term contributions. Moreover, as a consequence of additional D-term contributions to scalar masses, we obtain various soft supersymmetry breaking mass spectra, which are different from those obtained in the conventional anomaly mediation scenario. Then there would be a distinct signature of this scenario at the LHC. For example, in several cases, there exist mass splittings between the right-handed sfermion and the left-handed sfermion. We also discuss some characteristic features of the neutralino dark matter in this model.

hep-ph↗

Radiative B-L symmetry breaking and the Z' mediated SUSY breaking

We explore a mechanism of radiative B-L symmetry breaking in analogous to the radiative electroweak symmetry breaking. The breaking scale of B-L symmetry is related to the neutrino masses through the see-saw mechanism. Once we incorporate the U(1)_{B-L} gauge symmetry in SUSY models, the U(1)_{B-L} gaugino appears, and it can mediate the SUSY breaking (Z-prime mediated SUSY breaking) at around the scale of 10^6 GeV. Then we find a links between the neutrino mass (more precisly the see-saw or B-L scale of order 10^{6} GeV) and the Z-prime mediated SUSY breaking scale. It is also very interesting that the gluino at the weak scale becomes relatively light, and almost compressed mass spectra for the gaugino sector can be realized in this scenario, which is very interesting in scope of the LHC.

hep-ph↗

Unparticle Dark Matter

Once a parity is introduced in unparticle physics, under which unparticle provided in a hidden conformal sector is odd while all Standard Model particles are even, unparticle can be a suitable candidate for the cold dark matter (CDM) in the present universe through its coupling to the Standard Model Higgs doublet. We find that for Higgs boson mass in the range, 114.4 GeV < m_h < 250 GeV, the relic abundance of unparticle with mass 50 GeV < m_U < 80 GeV can be consistent with the currently observed CDM density. In this scenario, Higgs boson with mass m_h < 160 GeV dominantly decays into a pair of unparticles and such an invisible Higgs boson may be discovered in future collider experiments.

hep-ph↗

Constraint on the heavy sterile neutrino mixing angles in the SO(10) model with double see-saw mechanism

Constraints on the heavy sterile neutrino mixing angles are studied in the framework of a minimal supersymmetric ${\rm SO}(10)$ model with {\it double see-saw mechanism}. A new singlet matter in addition to the right-handed neutrinos is introduced to realize the double see-saw mechanism. The minimal ${\rm SO}(10)$ model gives an unambiguous Dirac neutrino mass matrix, which enables us to predict the masses and the mixing angles in the enlarged $9 \times 9$ neutrino mass matrix. Mixing angles between the light Majorana neutrinos and the heavy sterile neutrinos are shown to be within the LEP experimental bound on all ranges of the Majorana phases.

hep-ph↗

Unparticle physics at the photon collider

Recently, a conceptually new physics beyond the Standard Model (SM), unparticle, has been proposed, where a hidden conformal sector is coupled to the SM sector through higher dimensional operators. In this setup, we investigate unparticle physics at the photon collider, in particular, unparticle effects on the gamma gamma to gamma gamma process. Since this process occurs at loop level in the SM, the unparticle effects can be significant even if the cutoff scale is very high. In fact, we find that the unparticle effects cause sizable deviations from the SM results. The scaling dimension of the unparticle d_U reflects the dependence of the cross section on the final state photon invariant mass, so that precision measurements of this dependence may reveal the scaling dimension of the unparticle.

hep-ph↗