Stochastic resonance in a gain-noise model of a single-mode laser driven by pump noise and quantum noise with cross-correlation between real and imaginary parts under direct signal modulation

Stochastic resonance （SR） is studied in a gain-noise model of a single-mode laser driven by a coloured pump noise and a quantum noise with cross-correlation between real and imaginary parts under a direct signal modulation. By using a linear approximation method, we find that the SR appears during the variation of signal-to-noise ratio （SNR） separately with the pump noise self-correlation time τ, the noise correlation coefficient between the real part and the imaginary part of the quantum noise λq, the attenuation coefficient γ＇ and the deterministic steady-state intensity I0. In addition, it is found that the SR can be characterized not only by the dependence of SNR on the noise variables of and λq, but also by the dependence of SNR on the laser system variables of γ and I0. Thus our investigation extends the characteristic quantity of SR proposed before.

Origin of Negative Imaginary Part of Effective Permittivity of Passive Materials

The anti-resonant phenomenon of effective electromagnetic parameters of metamaterials has aroused controversy due to negative imaginary permittivity or permeability. It is experimentally found that the negative imaginary permittivity can occur for the natural passive materials near the Fabry Perot resonances. We reveal the nature of negative imaginary permittivity, which is correlated with the magnetoelectric coupling. The anti-resonance of permittivity is a non-inherent feature for passive materials, while it can be inherent for devices or metamaterials. Our finding validates that the negative imaginary part of effective permittivity does not contradict the second law of thermodynamics for metamaterials owing to the magnetoelectric coupling.

Why Do the Imaginary and Imaginary Communities Emerge in Social Theory? National Imaginary in the Context of Globalization

The end of modernism questions reality and its theoretical description,and various attempts of postmodern rethinking of the social emerge-from denial,assertion of the disappearance of the social to its salvation through radical rethinking.Theorizing around the imaginary emerges and continues as a result of this rethinking.Cornelius Castoriadis,for example,absolutizes the concept of the imaginary,which,in his opinion,even contains the rational.Charles Taylor gives imaginary,though important,but limited role as a background knowledge.Speaking of the imaginary,one cannot,of course,ignore Benedict Andersen’s imaginary communities.According to Andersen,the“imagination”of a nation,like any other community,reflects not the fact that they are“invented”or“constructed”but that they are the result of human practice,that social reality is a socio-historical and cultural product.Nation differs from other communities in the style of representation,namely,the representation-understanding,first of all,of space and time.A specific moment in time is connected not only with the past and future,but also with the same moment in another time and space measurement.People in this case,communicate and socialize through books,newspapers,and national languages.Most importantly,the nation as an imaginary community opposes itself to other communities,distinguishes itself from them,and strives for autonomy.And the guarantee of autonomy is the sovereign state,the nation-state,therefore the nation is always connected with the state and the territory of the exercise of its monopoly right.That is,the nation is an imaginary community that is real only to the extent that it is correlated with the modern territorial state.According to the author,the transformation of the national imaginary under the conditions of globalization is characterized by the loss of attachment to the territory,by the fact that territoriality ceases to be the main,organizing principle of social life.Social practices are increasingly formed beyond borders,belonging to ethnicity,national identity is not determined by territory and citizenship.Despite this,we must not forget that globalization is not a finished project.The transformation of the national imaginary should be viewed not only as the emergence of new imaginary communities,whether national or transnational,but also against the backdrop of interaction and even struggle between traditional forms of social practices and new ones,as evidenced by the growth of ethnic conflicts and separatist movements.According to Appudurai,this is also a consequence of globalization processes.And how this confrontation will end,the question remains open.

Physical insights from imaginary-time density–density correlation functions

An accurate theoretical description of the dynamic properties of correlated quantum many-body systems,such as the dynamic structure factor S(q,ω),is important in many fields.Unfortunately,highly accurate quantum Monte Carlo methods are usually restricted to the imaginary time domain,and the analytic continuation of the imaginary-time density–density correlation function F(q,τ)to real frequencies is a notoriously hard problem.Here,it is argued that often no such analytic continuation is required because by definition,F(q,τ)contains the same physical information as does S(q,ω),only represented unfamiliarly.Specifically,it is shown how one can directly extract key information such as the temperature or quasi-particle excitation energies from theτdomain,which is highly relevant for equation-of-state measurements of matter under extreme conditions[T.Dornheim et al.,Nat.Commun.13,7911(2022)].As a practical example,ab initio path-integral Monte Carlo results for the uniform electron gas(UEG)are considered,and it is shown that even nontrivial processes such as the roton feature of the UEG at low density[T.Dornheim et al.,Commun.Phys.5,304(2022)]are manifested straightforwardly in F(q,τ).A comprehensive overview is given of various useful properties of F(q,τ)and how it relates to the usual dynamic structure factor.In fact,working directly in theτdomain is advantageous for many reasons and opens up multiple avenues for future applications.

The Theoretical Significance and Reality of Imaginary Number

It is a fact that imaginary numbers do not have practical significance. But the role of imaginary numbers is very broad and enormous, due to the existence of Euler’s formula. Due to Euler’s formula, imaginary numbers have been applied in many theoretical theories. One of the biggest functions of imaginary numbers is to represent changes in phase, which is indispensable in signal analysis theory. The imaginary numbers in quantum mechanics pose a greater mystery: do the imaginary numbers really exist? This question still needs further scientific development to be answered.

Experimental Investigation of Lee–Yang Criticality Using Non-Hermitian Quantum System

Lee–Yang theory clearly demonstrates where the phase transition of many-body systems occurs and the asymptotic behavior near the phase transition using the partition function under complex parameters. The complex parameters make the direct investigation of Lee–Yang theory in practical systems challenging. Here we construct a non-Hermitian quantum system that can correspond to the one-dimensional Ising model with imaginary parameters through the equality of partition functions. By adjusting the non-Hermitian parameter,we successfully obtain the partition function under different imaginary magnetic fields and observe the Lee–Yang zeros. We also observe the critical behavior of free energy in vicinity of Lee–Yang zero that is consistent with theoretical prediction. Our work provides a protocol to study Lee–Yang zeros of the one-dimensional Ising model using a single-qubit non-Hermitian system.

Tunable Optical Bandgap of Gadolinium Substituted Nickel-Zinc Ferrite Nanoparticles-Effect of Calcination Temperature on Its Optical Parameters

The gadolinium substituted nickel-zinc ferrite nanoparticles of the composition, Ni0.5Zn0.5Gd0.05Fe1.95O4 were prepared using sol-gel method. In order to study the effect of calcination temperature on the optical parameters, the prepared powder was divided into five parts. The first part was taken as the as-prepared sample and the remaining four parts were calcinated at different temperatures, 600°C, 700°C, 800°C & 900°C. The X-ray diffraction patterns revealed the formation of cubic spinel structure with single phase and Fd3m space group. The crystallite size was increased from 11.75 nm to 18.13 nm as the calcination temperature increased from 600 to 900°C whereas as-prepared sample exhibited 17.61 nm. The dislocation density was decreased from 7.243 × 10-3 to 3.042 × 10-3 nm-2 as the calcination temperature increased from 600°C to 900°C. The micro strain was decreased from 10 × 10-4 to 6.452 × 10-4 as the calcination temperature increased from 600°C to 900°C. The characteristic absorbance peaks were obtained at 255.2 nm for the ferrite nanoparticles of as-prepared and calcinated at 600°C and 800°C whereas it was obtained as 252.8 nm for the sample calcinated at 700°C and there was no such characteristic peak in UV-visible range for the sample calcinated at 900°C;it is expected in the below 200 nm region. The optical energy gap was calculated using Kubelka-Munk equation based on Tauc’s plot and found in the range 4.100 eV to 5.389 eV. The lowest energy gap of 4.100 eV exhibited by the sample calcinated at 700°C and the highest energy gap of 5.389 eV by the sample calcinated at 900°C. It is concluded that the tunable band gaps can be obtained with varying calcination temperature.

“Sociotechnical Imaginary”的含义辨析及中译讨论

“Sociotechnical Imaginary”概念是分析科学技术与社会秩序共生现象的有力工具,被当代STS学者广泛采用。通过考察imaginary含义的发展过程,结合与STS中试图弥合主客二元的研究趋势,比较、辨析“Sociotechnical Imaginary”概念与其他近义词汇及社会意象、秩序工具、行动者网络等概念,可以认为“Sociotechnical Imaginary”是一种具备实在性、存于主客二元之间、有集体性、一定程度的规范性、稳定性、灵活性、多样性等多种特征的特殊想象形式。“社会技术意象”这一中文词汇能够较好地表达这一概念。

Physical Reality and Essence of Imaginary Numbers in Astrophysics: Dark Matter, Dark Energy, Dark Space

Dark matter and dark energy phenomenon which has been totally incomprehensible until very recently is explained by existence, besides our Universe, other invisible parallel universes in the hidden Multiverse. Such explanation of dark matter and dark energy phenomenon in astrophysics has become possible only after proving of the principle of physical reality of imaginary numbers discovered in mathematics 500 years ago. And the principle of physical reality of imaginary numbers has made the postulate of light speed non-exceedance in the special theory of relativity unnecessary. Therefore,?all relativistic formulas in this theory should be adjusted. As follows from the adjusted relativistic formulas, we live in Multiverse rather than in Monoverse. All parallel universes of the Multiverse are mutually invisible, therefore Multiverse is called hidden. WMAP and Planck data analysis has showed that the hidden Multiverse has a quaternion structure and contains 20?-?22 parallel universes, of which 5?-?6 are adjacent to our universe, and others are further. And these parallel universes are linked by unidirectional and bidirectional portals. Some portals link the hidden Multiverse with other Multiverses, which form a dark space. The multiverses of dark space together with the hidden Multiverse form Hyperverse.

Kernel polynomial representation for imaginary-time Green's functions in continuous-time quantum Monte Carlo impurity solver

Inspired by the recently proposed Legendre orthogonal polynomial representation for imaginary-time Green s functions G（τ）,we develop an alternate and superior representation for G（τ） and implement it in the hybridization expansion continuous-time quantum Monte Carlo impurity solver.This representation is based on the kernel polynomial method,which introduces some integral kernel functions to filter the numerical fluctuations caused by the explicit truncations of polynomial expansion series and can improve the computational precision significantly.As an illustration of the new representation,we re-examine the imaginary-time Green＇s functions of the single-band Hubbard model in the framework of dynamical mean-field theory.The calculated results suggest that with carefully chosen integral kernel functions,whether the system is metallic or insulating,the Gibbs oscillations found in the previous Legendre orthogonal polynomial representation have been vastly suppressed and remarkable corrections to the measured Green＇s functions have been obtained.

Imaginary displacement method for analysis of multi-fingered robot hands grasping stability

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Imaginary-Time Periodicity inŋ-ξSpacetime

The relations between the imaginary-time periodicity and the thermal Bogoliubov transformation inŋ-ξfield theory are discussed.It has been shown that the thermal Bogoliubov transformation leads to the imaginary-time periodicity of the Green function inŋ-ξspacetime and to the KMS condition.

Imaginary Time Crystal of Thermal Quantum Matter

Temperature is a fundamental thermodynamic variable for matter.Physical observables are often found to either increase or decrease with it,or show a non-monotonic dependence with peaks signaling underlying phase transitions or anomalies.Statistical Held theory has established connection between temperature and time:a quantum ensemble with inverse temperatureβis formally equivalent to a dynamic system evolving along an imaginary time from 0 to iβin the space one dimension higher.Here we report that a gas of hard-core bosons interacting with a thermal bath manifests an unexpected temperature-periodic oscillation of its macroscopic observables,arising from the microscopic origin of space-time locked translational symmetry breaking and crystalline ordering.Such a temperature crystal,supported by quantum Monte Carlo simulation,generalizes the concept of purely spatial density-wave order to the imaginary time axis for Euclidean action.

Motor imaginary-based BCI for controlling a remote car

This paper presents the application of an effective electroencephalogram(EEG)based brain-computer interface(BCI)for controlling a remote car in a practical environment.The BCI uses the motor imaginary to translate the subject’s motor intention into a control signal through classifying EEG patterns of different imaginary tasks.The system is composed of a remote car,a digital signal processor and a wireless data transfer module.The performance of the BCI was found to be robust to distract motor imaginary in the remote car controlling and need a short training time.The experimental results indicate that the successful ternary-control by using motor imaginry may be practicable in an uncontrolled environment.

Killing Imaginary Numbers? From Today’s Asymmetric Number System to a Symmetric System

In this paper, we point out an interesting asymmetry in the rules of fundamental mathematics between positive and negative numbers. Further, we show an alternative numerical system identical to today’s system, but where positive numbers dominate over negative numbers. This is like a mirror symmetry of the existing number system. The asymmetry in both systems leads to imaginary and complex numbers. We also suggest an alternative number system with perfectly symmetrical rules—that is, where there is no dominance of negative numbers over positive numbers or vice versa, and where imaginary and complex numbers are no longer needed. This number system seems to be superior to other numerical systems, as it brings simplicity and logic back to areas that complex rules have dominated for much of the history of mathematics. Finally, we also briefly discuss how the Riemann hypothesis may be linked to the asymmetry in the current number system. The foundation rules of a number system can, in general, not be proven incorrect or correct inside the number system itself. However, the ultimate goal of a number system is, in our view, to describe nature accurately. The optimal number system should therefore be developed with feedback from nature. If nature, at a very fundamental level, is ruled by symmetry, then a symmetric number system should make it easier to understand nature than an asymmetric number system would. We hypothesize that a symmetric number system may thus be better suited to describing nature. Further, such a number system should eliminate imaginary numbers in space-time and quantum mechanics, for example, two areas of physics that are clouded in mystery to this day.

Losing weight by eating an "imaginary meal in a pill"

A drug dubbed an'imaginary meal in a pill'is being developed by scientists. The pill tricks the body into thinking it has consumed a large amount of calories-as if you have just eaten a substantial meal. The dieter’s dream,it would allow them to continue to enjoy fatty foods without putting on weight. The drug,which tricks the body into believing it has eaten, also cuts cholesterol and keeps blood sugar levels under control.

On the Symbolic Meaning of Imaginary Son in Who’s Afraid of Virginia Woolf?

According to the relationship between symbol and meaning in semiotics,this paper analyzes the symbolic meaning of the imaginary son and the meaning of killing him in Albee’s Who’s Afraid of Virginia Woolf?,and concludes that killing the imaginary son is the only way to escape the bondage of rigid social morality and come back to the reality.

Topological states switching and group velocity control in two-dimensional non-reciprocal Hermitian photonic lattice

We proposed a model with non reciprocal coupling coefficients, in which the imaginary parts γ indicate the phase delay or exceed term. The distributions of band structure and the group velocity are both characterized as a function of the coupling. we studied the system’s topological states and group velocity control. The results show that the movement and breaking of Dirac points exist in the energy band of the system. By changing the coupling coefficients, the conversion between any topological states corresponds to different Chern number. Topological edge states exist in topological nontrivial systems that correspond to the two different Chern numbers. Besides, it is also found that both the coupling coefficient and the wave vector can cause the oscillation of the pulse group velocity. At the same time, the topological state can suppress the amplitude of the group velocity profiles. Our findings enrich the theory of light wave manipulation in high-dimensional photonic lattices and provide a novel view for realizing linear localization and group velocity regulation of light waves,which has potential application in high-speed optical communication and quantum information fields.

Realizing quantum imaginary time evolution in experiment

NISQ,or Noisy Intermediate-Scale Quantum computing,represents a pivotal and the state-of-the-art quantum technology[1].Characterized by intermediate-scale quantum devices that are beyond classical computational capabilities yet fall short of the error-correction thresholds required for fault-tolerant quantum computing,NISQ devices exhibit both promise and challenges.NISQ devices hold immense potential in solving certain computational problems that surpass classical capabilities,with wide applications in optimization,machine learning,and quantum chemistry.

Absorption Properties of Urban/Suburban Aerosols in China

The broadband diffuse radiation method is improved to retrieve the aerosol refractive index imaginary part （AIP） and broadband （400-1000 nm mean） single scattering albedo （SSA）. In this method, four sets of SSA selection criteria are proposed for quality control. The method is used to retrieve AIP, SSA and absorptive optical thickness （AbOT） from routine hourly-exposed pyrheliometer and paranometer measurements over 11 sites （meteorological observatories） in China during 1998-2003. Apart from one suburban site （Ejin Qi）, the other urban sites are all located around big or medium cities. As shown in the retrieval results, annual mean SSA during 1998-2003 changes from 0.941 （Wuhan） to 0.849 （Lanzhou）, and AIP from 0.0054 to 0.0203. The 11-site average annual mean SSA and AIP are 0.898 and 0.0119, respectively. SSA during winter is smaller for most sites. There is an evidently positive correlation between SSA and aerosol optical thickness （AOT） for all sites. There is also a positive correlation between SSA and relative humidity for most sites, but a negative correlation for a few sites, such as Kashi and ǚrǚmqi in Northwest China.