The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Harald Fritzsch - One of the best experts on this subject based on the ideXlab platform.
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Running vacuum in the Universe and the Time Variation of the fundamental constants of Nature
The European Physical Journal C, 2017Co-Authors: Harald Fritzsch, Joan Sola, Rafael C. NunesAbstract:We compute the Time Variation of the fundamental constants (such as the ratio of the proton mass to the electron mass, the strong coupling constant, the fine structure constant and Newton's constant) within the context of the so-called running vacuum models (RVM's) of the cosmic evolution. Recently, compelling evidence has been provided showing that these models are able to fit the main cosmological data (SNIa+BAO+H(z)+LSS+BBN+CMB) significantly better than the concordance $\Lambda$CDM model. Specifically, the vacuum parameters of the RVM (i.e. those responsible for the dynamics of the vacuum energy) prove to be nonzero at a confidence level $\gtrsim3\sigma$. Here we use such remarkable status of the RVM's to make definite predictions on the cosmic Time Variation of the fundamental constants. It turns out that the predicted Variations are close to the present observational limits. Furthermore, we find that the Time Variation of the dark matter particles should be crucially involved in the total mass Variation of our Universe. A positive measurement of this kind of effects could be interpreted as strong support to the "micro and macro connection" (viz. the dynamical feedback between the evolution of the cosmological parameters and the Time Variation of the fundamental constants of the microscopic world), previously proposed by two of us (HF and JS).
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running vacuum in the universe and the Time Variation of the fundamental constants of nature
European Physical Journal C, 2017Co-Authors: Harald Fritzsch, Joan Sola, Rafael C. NunesAbstract:We compute the Time Variation of the fundamental constants (such as the ratio of the proton mass to the electron mass, the strong coupling constant, the fine-structure constant and Newton’s constant) within the context of the so-called running vacuum models (RVMs) of the cosmic evolution. Recently, compelling evidence has been provided that these models are able to fit the main cosmological data (SNIa+BAO+H(z)+LSS+BBN+CMB) significantly better than the concordance $$\Lambda $$ CDM model. Specifically, the vacuum parameters of the RVM (i.e. those responsible for the dynamics of the vacuum energy) prove to be nonzero at a confidence level $${\gtrsim } 3\sigma $$ . Here we use such remarkable status of the RVMs to make definite predictions on the cosmic Time Variation of the fundamental constants. It turns out that the predicted Variations are close to the present observational limits. Furthermore, we find that the Time evolution of the dark matter particle masses should be crucially involved in the total mass Variation of our Universe. A positive measurement of this kind of effects could be interpreted as strong support to the “micro–macro connection” (viz. the dynamical feedback between the evolution of the cosmological parameters and the Time Variation of the fundamental constants of the microscopic world), previously proposed by two of us (HF and JS).
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LIMITS ON THE Time Variation OF FUNDAMENTAL CONSTANTS
Modern Physics Letters A, 2008Co-Authors: Harald FritzschAbstract:We discuss possible Time changes of the 28 fundamental constants of the Standard Model of Particle Physics. In particular, we concentrate on those constants, which are not known very precisely. Time Variations of those constants might have been overlooked thus far. Future experiments should provide better limits, or might discover a Time Variation.
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A Time Variation of Proton-Electron Mass Ratio and Grand Unification
EPL, 2006Co-Authors: Xavier Calmet, Harald FritzschAbstract:Astrophysical observations indicate a Time Variation of the proton-electron mass ratio and of the fine-structure constant. We discuss this phenomenon in models of Grand Unification. In these models a Time Variation of the fine-structure constant and of the proton mass are expected, if either the unified coupling constant or the scale of unification changes, or both change. We discuss in particular the change of the proton mass. Experiments in Quantum Optics could be done to check these ideas.
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A Time Variation of the QCD Scale
Beyond the Desert 2003, 2004Co-Authors: Harald FritzschAbstract:Astrophysical indications that the fine structure constant has undergone a small Time Variation during the cosmological evolution are discussed within the framework of the standard model of the electroweak and strong interactions and of grand unification. A Variation of the electromagnetic coupling constant could either be generated by a corresponding Time Variation of the unified coupling constant or by a Time Variation of the unification scale, of by both. The various possibilities, differing substantially in their implications for the Variation of low energy physics parameters like the nuclear mass scale, are discussed. The case in which the Variation is caused by a Time Variation of the unification scale is of special interest.
Mengchu Zhou - One of the best experts on this subject based on the ideXlab platform.
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real Time scheduling of single arm cluster tools subject to residency Time constraints and bounded activity Time Variation
IEEE Transactions on Automation Science and Engineering, 2012Co-Authors: Yan Qiao, Naiqi Wu, Mengchu ZhouAbstract:It is very challenging to schedule cluster tools subject to wafer residency Time constraints and activity Time Variation. This work develops a Petri net model to describe the system and proposes a two-level real-Time scheduling architecture. At the lower level, a real-Time control policy is used to offset the activity Time Variation as much as possible. At the upper level, a periodical off-line schedule is derived under the normal condition. This work presents the schedulability conditions and scheduling algorithms for an off-line schedule. The schedulability conditions can be analytically checked. If they are satisfied, an off-line schedule can be analytically found. The off-line schedule together with a real-Time control policy forms the real-Time schedule for the system. It is optimal in terms of cycle Time minimization. Illustrative examples are given to show the application of the proposed approach. Note to Practitioners-This paper discusses the real-Time scheduling problem of single-arm cluster tools with wafer residency Time constraints and bounded activity Time Variation. With a Petri net model, schedulability is analyzed and schedulability conditions are presented by using analytical expressions. Then, an efficient algorithm is proposed to find a periodical schedule if it is schedulable. Such a schedule is optimal in terms of cycle Time and can adapt to bounded activity Time Variation. Therefore, it is applicable to the scheduling and real-Time control of cluster tools in semiconductor manufacturing plants.
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modeling analysis and control of dual arm cluster tools with residency Time constraint and activity Time Variation based on petri nets
IEEE Transactions on Automation Science and Engineering, 2012Co-Authors: Mengchu ZhouAbstract:Because of residency Time constraints and activity Time Variation of cluster tools, it is very difficult to operate such integrated semiconductor manufacturing equipment. This paper addresses their real-Time operational issues. To characterize their schedulability and achieve the minimum cycle Time at their steady-state operation, Petri net (PN) models are developed to describe them, which are very compact, and independent of wafer flow pattern. It is due to the proposed models that scheduling cluster tools is converted into determining robot wait Times. A two-level operational architecture is proposed to include an offline periodic schedule and real-Time controller. The former determines when a wafer should be placed into a process module for processing, while the latter regulates robot wait Times online in order to reduce the effect of activity Time Variation on wafer sojourn Times in process modules. Therefore, the system can adapt to activity Time Variation. A cluster tool derived as a not-always-schedulable system by the existing methods is shown to be always-schedulable by using the proposed novel method.
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schedulability analysis and optimal scheduling of dual arm cluster tools with residency Time constraint and activity Time Variation
IEEE Transactions on Automation Science and Engineering, 2012Co-Authors: Mengchu ZhouAbstract:With wafer residency Time constraint of cluster tools in semiconductor manufacturing, activity Time Variation can make an originally feasible schedule infeasible. Thus, it is difficult to schedule them and schedulability is a vitally important issue. With bounded activity Time Variation considered, this paper addresses their real-Time scheduling issues and conducts their schedulability analysis. A Petri net (PN) model and a control policy are presented. Based on them, this paper derives closed-form schedulability conditions. If schedulable, an algorithm is developed to obtain an offline periodic schedule. This schedule together with the control policy forms a real-Time schedule. It is optimal in terms of cycle Time and can be analytically computed, which represents significant advance in this area.
Xavier Calmet - One of the best experts on this subject based on the ideXlab platform.
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A Time Variation of Proton-Electron Mass Ratio and Grand Unification
EPL, 2006Co-Authors: Xavier Calmet, Harald FritzschAbstract:Astrophysical observations indicate a Time Variation of the proton-electron mass ratio and of the fine-structure constant. We discuss this phenomenon in models of Grand Unification. In these models a Time Variation of the fine-structure constant and of the proton mass are expected, if either the unified coupling constant or the scale of unification changes, or both change. We discuss in particular the change of the proton mass. Experiments in Quantum Optics could be done to check these ideas.
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Grand Unification and Time Variation of the Gauge Couplings
arXiv: High Energy Physics - Phenomenology, 2002Co-Authors: Xavier Calmet, Harald FritzschAbstract:Astrophysical indications that the fine structure constant is Time dependent are discussed in the framework of grand unification models. A Variation of the electromagnetic coupling constant could either be generated by a corresponding Time Variation of the unified coupling constant or by a Time Variation of the unification scale, or by both. The case in which the Time Variation of the electromagnetic coupling constant is caused by a Time Variation of the unification scale is of special interest. It is supported in addition by recent hints towards a Time change of the proton-electron mass ratio. Possible implications for baryogenesis are discussed.
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Grand Unification and Time Variation of the Gauge Couplings
Supersymmetry and unification of fundamental interactions, 2002Co-Authors: Xavier Calmet, Harald FritzschAbstract:Astrophysical indications that the fine structure constant is Time dependent are discussed in the framework of grand unification models. A Variation of the electromagnetic coupling constant could either be generated by a corresponding Time Variation of the unified coupling constant or by a Time Variation of the unification scale, or by both. The case in which the Time Variation of the electromagnetic coupling constant is caused by a Time Variation of the unification scale is of special interest. It is supported in addition by recent hints towards a Time change of the proton-electron mass ratio. Possible implications for baryogenesis are discussed. The study of a possible Time Variation of the fundamental parameters like for example the fine structure constant, has a long history that can be traced back to Dirac [1]. Some extensions of the standard model of particle physics and in particular models that couple gravity to the standard model, e.g. quintessence [2], require or at least allow a Time dependence of the parameters of the model. Our motivation to study the implications of a Time dependence of the fundamental parameters for particle physics is not that much of a theoretical origin but rather because there are indications [3, 4, 5, 6, 7, 8] coming from different astrophysical measurements that the parameters of the standard model could be Time dependent. We shall consider the implications of Webb et al.’s result which indicate a possible Time dependence of "
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Symmetry breaking and Time Variation of gauge couplings
Physics Letters B, 2002Co-Authors: Xavier Calmet, Harald FritzschAbstract:Astrophysical indications that the fine structure constant has undergone a small Time Variation during the cosmological evolution are discussed within the framework of the standard model of the electroweak and strong interactions and of grand unification. A Variation of the electromagnetic coupling constant could either be generated by a corresponding Time Variation of the unified coupling constant or by a Time Variation of the unification scale, of by both. The various possibilities, differing substantially in their implications for the Variation of low energy physics parameters like the nuclear mass scale, are discussed. The case in which the Variation is caused by a Time Variation of the unification scale is of special interest. It is supported in addition by recent hints towards a Time change of the proton-electron mass ratio. Implications for the analysis of the Oklo remains and for quantum optics tests are discussed.
Rafael C. Nunes - One of the best experts on this subject based on the ideXlab platform.
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Running vacuum in the Universe and the Time Variation of the fundamental constants of Nature
The European Physical Journal C, 2017Co-Authors: Harald Fritzsch, Joan Sola, Rafael C. NunesAbstract:We compute the Time Variation of the fundamental constants (such as the ratio of the proton mass to the electron mass, the strong coupling constant, the fine structure constant and Newton's constant) within the context of the so-called running vacuum models (RVM's) of the cosmic evolution. Recently, compelling evidence has been provided showing that these models are able to fit the main cosmological data (SNIa+BAO+H(z)+LSS+BBN+CMB) significantly better than the concordance $\Lambda$CDM model. Specifically, the vacuum parameters of the RVM (i.e. those responsible for the dynamics of the vacuum energy) prove to be nonzero at a confidence level $\gtrsim3\sigma$. Here we use such remarkable status of the RVM's to make definite predictions on the cosmic Time Variation of the fundamental constants. It turns out that the predicted Variations are close to the present observational limits. Furthermore, we find that the Time Variation of the dark matter particles should be crucially involved in the total mass Variation of our Universe. A positive measurement of this kind of effects could be interpreted as strong support to the "micro and macro connection" (viz. the dynamical feedback between the evolution of the cosmological parameters and the Time Variation of the fundamental constants of the microscopic world), previously proposed by two of us (HF and JS).
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running vacuum in the universe and the Time Variation of the fundamental constants of nature
European Physical Journal C, 2017Co-Authors: Harald Fritzsch, Joan Sola, Rafael C. NunesAbstract:We compute the Time Variation of the fundamental constants (such as the ratio of the proton mass to the electron mass, the strong coupling constant, the fine-structure constant and Newton’s constant) within the context of the so-called running vacuum models (RVMs) of the cosmic evolution. Recently, compelling evidence has been provided that these models are able to fit the main cosmological data (SNIa+BAO+H(z)+LSS+BBN+CMB) significantly better than the concordance $$\Lambda $$ CDM model. Specifically, the vacuum parameters of the RVM (i.e. those responsible for the dynamics of the vacuum energy) prove to be nonzero at a confidence level $${\gtrsim } 3\sigma $$ . Here we use such remarkable status of the RVMs to make definite predictions on the cosmic Time Variation of the fundamental constants. It turns out that the predicted Variations are close to the present observational limits. Furthermore, we find that the Time evolution of the dark matter particle masses should be crucially involved in the total mass Variation of our Universe. A positive measurement of this kind of effects could be interpreted as strong support to the “micro–macro connection” (viz. the dynamical feedback between the evolution of the cosmological parameters and the Time Variation of the fundamental constants of the microscopic world), previously proposed by two of us (HF and JS).
Joan Sola - One of the best experts on this subject based on the ideXlab platform.
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Running vacuum in the Universe and the Time Variation of the fundamental constants of Nature
The European Physical Journal C, 2017Co-Authors: Harald Fritzsch, Joan Sola, Rafael C. NunesAbstract:We compute the Time Variation of the fundamental constants (such as the ratio of the proton mass to the electron mass, the strong coupling constant, the fine structure constant and Newton's constant) within the context of the so-called running vacuum models (RVM's) of the cosmic evolution. Recently, compelling evidence has been provided showing that these models are able to fit the main cosmological data (SNIa+BAO+H(z)+LSS+BBN+CMB) significantly better than the concordance $\Lambda$CDM model. Specifically, the vacuum parameters of the RVM (i.e. those responsible for the dynamics of the vacuum energy) prove to be nonzero at a confidence level $\gtrsim3\sigma$. Here we use such remarkable status of the RVM's to make definite predictions on the cosmic Time Variation of the fundamental constants. It turns out that the predicted Variations are close to the present observational limits. Furthermore, we find that the Time Variation of the dark matter particles should be crucially involved in the total mass Variation of our Universe. A positive measurement of this kind of effects could be interpreted as strong support to the "micro and macro connection" (viz. the dynamical feedback between the evolution of the cosmological parameters and the Time Variation of the fundamental constants of the microscopic world), previously proposed by two of us (HF and JS).
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running vacuum in the universe and the Time Variation of the fundamental constants of nature
European Physical Journal C, 2017Co-Authors: Harald Fritzsch, Joan Sola, Rafael C. NunesAbstract:We compute the Time Variation of the fundamental constants (such as the ratio of the proton mass to the electron mass, the strong coupling constant, the fine-structure constant and Newton’s constant) within the context of the so-called running vacuum models (RVMs) of the cosmic evolution. Recently, compelling evidence has been provided that these models are able to fit the main cosmological data (SNIa+BAO+H(z)+LSS+BBN+CMB) significantly better than the concordance $$\Lambda $$ CDM model. Specifically, the vacuum parameters of the RVM (i.e. those responsible for the dynamics of the vacuum energy) prove to be nonzero at a confidence level $${\gtrsim } 3\sigma $$ . Here we use such remarkable status of the RVMs to make definite predictions on the cosmic Time Variation of the fundamental constants. It turns out that the predicted Variations are close to the present observational limits. Furthermore, we find that the Time evolution of the dark matter particle masses should be crucially involved in the total mass Variation of our Universe. A positive measurement of this kind of effects could be interpreted as strong support to the “micro–macro connection” (viz. the dynamical feedback between the evolution of the cosmological parameters and the Time Variation of the fundamental constants of the microscopic world), previously proposed by two of us (HF and JS).
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Fundamental Constants in Physics and Their Time Variation: Preface
Modern Physics Letters A, 2015Co-Authors: Joan SolaAbstract:There is no doubt that the field of Fundamental Constants in Physics and Their Time Variation is one of the hottest subjects in modern theoretical and experimental physics, with potential implications in all fundamental areas of physics research, such as particle physics, gravitation, astrophysics and cosmology. In this Special Issue, the state-of-the-art in the field is presented in detail.
