Pub Date : 2022-09-16DOI: 10.4249/scholarpedia.55237
Ignacio Garc'ia-Mata, R. Jalabert, D. Wisniacki
Quantum Chaos has originally emerged as the field which studies how the properties of classical chaotic systems arise in their quantum counterparts. The growing interest in quantum many-body systems, with no obvious classical meaning has led to consider time-dependent quantities that can help to characterize and redefine Quantum Chaos. This article reviews the prominent role that the out of time ordered correlator (OTOC) plays to achieve such goal.
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Pub Date : 2021-06-11DOI: 10.4249/scholarpedia.2433
Julian Lim, D. Dinges
Five constructs are taken into considerations to define pre-existing differences between subjects experience with: • Software development in general (DEV) • Test-driven developmet (TDD) • The Java programming language (OOP) • unit testing (UT) • the Eclipse IDE (IDE) for each of the four above (i.e., excluding TDD), we asked the subjects to evaluate: 1. general familiarity (5-points likert item: very experienced – very inexperienced ) 2. years used in academia (numerical integer) 3. years used in industry (numerical integer) 4. years used in own activities (numerical integer) Whereas we only have 1) regarding TDD. The alpha level is 0.0125 due to Bonferroni correction (i.e., taking into account the four measure above)
我们考虑了五种结构来定义受试者之间已有的差异:•通用软件开发(DEV)•测试驱动开发(TDD)•Java编程语言(OOP)•单元测试(UT)•Eclipse IDE (IDE)对于上述四种(即，不包括TDD)中的每一种，我们要求受试者评估:1。一般熟悉度(每项5分:非常有经验-非常没有经验)学术研究年限(数字整数)工业使用年限(数字整数)在自己的活动中使用的年数(数值整数)，而在TDD方面，我们只有1)。由于Bonferroni校正，alpha水平为0.0125(即，考虑到上述四个度量)
{"title":"Sleep deprivation","authors":"Julian Lim, D. Dinges","doi":"10.4249/scholarpedia.2433","DOIUrl":"https://doi.org/10.4249/scholarpedia.2433","url":null,"abstract":"Five constructs are taken into considerations to define pre-existing differences between subjects experience with: • Software development in general (DEV) • Test-driven developmet (TDD) • The Java programming language (OOP) • unit testing (UT) • the Eclipse IDE (IDE) for each of the four above (i.e., excluding TDD), we asked the subjects to evaluate: 1. general familiarity (5-points likert item: very experienced – very inexperienced ) 2. years used in academia (numerical integer) 3. years used in industry (numerical integer) 4. years used in own activities (numerical integer) Whereas we only have 1) regarding TDD. The alpha level is 0.0125 due to Bonferroni correction (i.e., taking into account the four measure above)","PeriodicalId":74760,"journal":{"name":"Scholarpedia journal","volume":"2 1","pages":"2433"},"PeriodicalIF":0.0,"publicationDate":"2021-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70973503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-09-02DOI: 10.4249/scholarpedia.55031
D. Shepelyansky
The Ehrenfest time gives the scale of time on which the Bohr correspondence principle (Bohr, 1920) remains valid for a quantum evolution of an initial state at high characteristic quantum numbers (or small effective Planck constant ) closely following the corresponding classical distribution. For a narrow initial wave packet the Ehrenfest theorem (Ehrenfest, 1927) guaranties that the average values of quantum operators are close to the corresponding classical averages. For systems with integrable classical dynamics the Ehrenfest time is rather long being generally inversely proportional to the Planck constant (or another power of it). The new nontrivial situation appears for classically chaotic dynamics when nearby trajectories diverge exponentially with time due to exponential instability of motion characterized by the positive Kolmogorov-Sinai entropy . Thus in such semiclassical systems the Ehrenfest time is logarithmically short . The properties of the Ehrenfest time of quantum dynamics of such chaotic systems, with related examples, are discussed below.
{"title":"Ehrenfest time and chaos","authors":"D. Shepelyansky","doi":"10.4249/scholarpedia.55031","DOIUrl":"https://doi.org/10.4249/scholarpedia.55031","url":null,"abstract":"The Ehrenfest time gives the scale of time on which the Bohr correspondence principle (Bohr, 1920) remains valid for a quantum evolution of an initial state at high characteristic quantum numbers (or small effective Planck constant ) closely following the corresponding classical distribution. For a narrow initial wave packet the Ehrenfest theorem (Ehrenfest, 1927) guaranties that the average values of quantum operators are close to the corresponding classical averages. For systems with integrable classical dynamics the Ehrenfest time is rather long being generally inversely proportional to the Planck constant (or another power of it). The new nontrivial situation appears for classically chaotic dynamics when nearby trajectories diverge exponentially with time due to exponential instability of motion characterized by the positive Kolmogorov-Sinai entropy . Thus in such semiclassical systems the Ehrenfest time is logarithmically short . The properties of the Ehrenfest time of quantum dynamics of such chaotic systems, with related examples, are discussed below.","PeriodicalId":74760,"journal":{"name":"Scholarpedia journal","volume":"15 1","pages":"55031"},"PeriodicalIF":0.0,"publicationDate":"2020-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49312103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-08-01DOI: 10.4249/scholarpedia.30710
R. Machleidt
Nuclear forces (also known as nuclear interactions or strong forces) are the forces that act between two or more nucleons. They bind protons and neutrons (“nucleons”) into atomic nuclei. The nuclear force is about 10 millions times stronger than the chemical binding that holds atoms together in molecules. This is the reason why nuclear reactors produce about a million times more energy per kilogram fuel as compared to chemical fuel like oil or coal. However, the range of the nuclear force is short, only a few femtometer (1 fm = 10^{15} m), beyond which it decreases rapidly. That is why, in spite of its enormous strength, we do not feel anything of this force on the atomic scale or in everyday life. The development of a proper theory of nuclear forces has occupied the minds of some of the brightest physicists for seven decades and has been one of the main topics of physics research in the 20th century. The original idea was that the force is caused by the exchange of particles lighter than nucleons known as mesons, and this idea gave rise to the birth of a new subfield of modern physics, namely, (elementary) particle physics. The modern perception of the nuclear force is that it is a residual interaction (similar to the van der Waals force between neutral atoms) of the even stronger force between quarks, which is mediated by the exchange of gluons and holds the quarks together inside a nucleon.
{"title":"Nuclear Forces","authors":"R. Machleidt","doi":"10.4249/scholarpedia.30710","DOIUrl":"https://doi.org/10.4249/scholarpedia.30710","url":null,"abstract":"Nuclear forces (also known as nuclear interactions or strong forces) are the forces that act between two or more nucleons. They bind protons and neutrons (“nucleons”) into atomic nuclei. The nuclear force is about 10 millions times stronger than the chemical binding that holds atoms together in molecules. This is the reason why nuclear reactors produce about a million times more energy per kilogram fuel as compared to chemical fuel like oil or coal. However, the range of the nuclear force is short, only a few femtometer (1 fm = 10^{15} m), beyond which it decreases rapidly. That is why, in spite of its enormous strength, we do not feel anything of this force on the atomic scale or in everyday life. The development of a proper theory of nuclear forces has occupied the minds of some of the brightest physicists for seven decades and has been one of the main topics of physics research in the 20th century. The original idea was that the force is caused by the exchange of particles lighter than nucleons known as mesons, and this idea gave rise to the birth of a new subfield of modern physics, namely, (elementary) particle physics. The modern perception of the nuclear force is that it is a residual interaction (similar to the van der Waals force between neutral atoms) of the even stronger force between quarks, which is mediated by the exchange of gluons and holds the quarks together inside a nucleon.","PeriodicalId":74760,"journal":{"name":"Scholarpedia journal","volume":"9 1","pages":"30710"},"PeriodicalIF":0.0,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42916262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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