Thermodynamics is more powerful than the role to it reserved by Boltzmann-Gibbs statistical mechanics

We briefly review the connection between statistical mechanics and thermodynamics. We show that, in order to satisfy thermo-dynamics and its Legendre transformation mathematical frame, the celebrated Boltzmann-Gibbs (BG) statistical mechanics is sufficient but not necessary. Indeed, the N →∞ limit of statistical mechanics is expected to be consistent with thermodynamics. For systems whose elements are generically independent or quasi-independent in the sense of the theory of probabilities, it is well known that the BG theory (based on the additive BG entropy) does satisfy this expectation. However, in complete analogy, other thermostatistical theories (e.g., q-statistics), based on nonadditive entropic functionals, also satisfy the very same expectation. We illustrate this standpoint with systems whose elements are strongly correlated in a specific manner, such that they escape the BG realm.     

脑磁图仪的前世今生与未来

脑磁图仪通过记录大脑神经活动在头皮外产生的磁场来进行脑活动的成像,它具备超高的时间分辨率和较高的空间分辨率,是一种重要的无创脑功能成像技术。文章介绍了脑磁信号的神经生理起源、生物物理特征及其与脑电信号的联系和区别,回顾了当前基于超导量子干涉仪的脑磁图设备与相关技术,并针对制约当前超导脑磁图发展的技术瓶颈,介绍了基于原子磁强计的新型脑磁探测技术及国内相关研究的最新进展,指出了脑磁图在脑科学研究及临床应用中不可或缺的地位和其硬件技术未来发展的方向。     

Entanglement between the future and the past in the quantum vacuum

We note that massless fields within the future and past light cone may be quantized as independent systems. The vacuum is shown to be a nonseparable state of these systems, exactly mirroring the known entanglement between the spacelike separated Rindler wedges. This leads to a notion of timelike entanglement. We describe an inertial detector which exhibits a thermal response to the vacuum when switched on at t=0, due to this property. The feasibility of detecting this effect is discussed, with natural experimental parameters appearing at the scale of 100?GHz.     

CP violation: the past, the present and the future

We have just entered a period during which we expect considerable progress toward understanding CP violation. Here we review what we have learnt so far, and what is to be expected in the near future. To do this we cover the foundation of CP violation at a level which can be understood by physicists who are not working in this field.     

Hyperfine interactions: the past, the present and the future

Five major hyperfine interaction techniques, detected by nuclear radiation, originated in the short time span between 1950 and 1965. The coincidence with the demographic expansion, especially in Europe, of university education led to the creation of many new research laboratories applying these promising techniques in solid state physics, chemistry and biology. Since the turn of century many of the early pioneers are going into retirement, leading to a decline in activities in Europe, compensated in some degree by an increase in activities outside Europe. The organisation of the 2007 HI/NQI-conference was impeccable and took place in a superb setting. Thanks to all those involved in its organization.     

Why is the universe so large?

S. W. Hawking's proposal for the wave function of the universe, if correct, determines the conditional probabilities for all properties of the universe. In a simple minisuperspace model it predicts that at any given nonzero energy density, the universe is most probably infinitely large.     

When hydrogen is slower than methane to ignite

Hydrogen (H₂) is known to be the fastest fuel to ignite among all practical combustion fuels. In this study, for the first time, longer ignition delay times (IDTs) for the H₂ and H₂ blended CH₄ mixtures were measured compared to those for pure CH₄. This work investigates the ignition characteristics of H₂, CH₄, and 50% CH₄/50% H₂ mixtures using a rapid compression machine at pressures ranging from 20 to 50 bar and at equivalence ratios (φ) from 0.5 to 2.0 in air in the temperature range 858–1080 K. The experimental IDTs are simulated using a newly updated kinetic mechanism, NUIGMech1.3, and good agreement is observed. At lower temperatures the IDTs of H₂, CH₄, and the 50% CH₄/50% H₂ mixtures are similar to one another, and the IDTs of the 50% CH₄/50% H₂ mixtures are longer than those for pure CH₄ at temperatures below 930 K. At temperatures below 890–925 K, depending on the operating pressure and equivalence ratio, the hydrogen mixtures are the slowest to ignite, with IDTs being 2.5 times longer than those recorded for CH₄ at a pressure of 40 bar at 890 K for φ = 1.0, and at 875 K for φ = 2.0. At low temperatures alkyl (Ṙ = ĊH₃ and Ḣ) radicals add to O₂ producing RȮ₂ radicals, which then react with HȮ₂ radicals forming ROOH (H₂O₂ and CH₃OOH) and O₂. For H₂, the self-recombination of HȮ₂ radicals leads to chain propagation which inhibits reactivity, whereas for CH₄, the reaction between RȮ₂ (CH₃OȮ) and HȮ₂ leads to chain branching, increasing reactivity. Furthermore, CH₃OOH decomposes more easily to produce CH₃Ȯ and ȮH radicals than does H₂O₂ to produce two ȮH radicals. Thus, mixtures containing higher H₂ concentrations are slower to ignite compared to those with higher CH₄ concentrations at low temperatures.     

Why the constituent interchange model does not predict the dimensional counting rule to any finite order in QCD

We demonstrate that the constitutent interchange diagram for nucleon nucleon elastic scattering contains a pinch singularity. This means that it predicts that \(\frac{{d\sigma }}{{dt}} \sim s^{ - 9} f\left( \theta \right)\) for high energy elastic scattering, at least to any finite order in QCD. We also show how the dimensional counting rule may perhaps be recovered by summing a suitable infinite series of graphs.     

Why there is something rather than nothing: cosmological constant from summing over everything in lorentzian quantum gravity

The density matrix of the Universe for the microcanonical ensemble in quantum cosmology describes an equipartition in the physical phase space of the theory (sum over everything), but in terms of the observable spacetime geometry this ensemble is peaked about the set of recently obtained cosmological instantons limited to a bounded range of the cosmological constant. This suggests the mechanism of constraining the landscape of string vacua and a possible solution to the dark energy problem in the form of the quasiequilibrium decay of the microcanonical state of the Universe.     

Why temperature chaos in spin glasses is hard to observe

The overlap length of a three-dimensional Ising spin glass on a cubic lattice with Gaussian interactions has been estimated numerically by transfer matrix methods and within a Migdal-Kadanoff renormalization group scheme. We find that the overlap length is large, explaining why it has been difficult to observe spin glass chaos in numerical simulations and experiment.     

Why nanoprojectiles work differently than macroimpactors: the role of plastic flow

Atomistic simulation data on crater formation due to the hypervelocity impact of nanoprojectiles of up to 55 nm diameter and with targets containing up to 1.1×10(10) atoms are compared to available experimental data on μm-, mm-, and cm-sized projectiles. We show that previous scaling laws do not hold in the nanoregime and outline the reasons: within our simulations we observe that the cratering mechanism changes, going from the smallest to the largest simulated scales, from an evaporative regime to a regime where melt and plastic flow dominate, as is expected in larger microscale experiments. The importance of the strain-rate dependence of strength and of dislocation production and motion are discussed.     

Why the Disjunction in Quantum Logic is Not Classical

In this paper, the quantum logical or is analyzed from a physical perspective. We show that it is the existence of EPR-like correlation states for the quantum mechanical entity under consideration that make it nonequivalent to the classical situation. Specifically, the presence of potentiality in these correlation states gives rise to the quantum deviation from the classical logical or. We show how this arises not only in the microworld, but also in macroscopic situations where EPR-like correlation states are present. We investigate how application of this analysis to concepts could alleviate some well known problems in cognitive science.     

Why is the conclusion of the Gerda experiment not justified

The first results of the GERDA double beta experiment in Gran Sasso were recently presented. They are fully consistent with the HEIDELBERG-MOSCOW experiment, but because of its low statistics cannot proof anything at this moment. It is no surprise that the statistics is still far from being able to test the signal claimed by the HEIDELBERG-MOSCOW experiment. The energy resolution of the coaxial detectors is a factor of 1.5 worse than in the HEIDELBERG-MOSCOW experiment. The original goal of background reduction to 10^?2 counts/kg y keV, or by an order of magnitude compared to the HEIDELBERG-MOSCOW experiment, has not been reached. The background is only a factor 2.3 lower if we refer it to the experimental line width, i.e. in units counts/kg y energy resolution. With pulse shape analysis (PSA) the back-ground in the HEIDELBERG-MOSCOW experiment around Q _ββ is 4 × 10^?3 counts/kg y keV [1], which is a factor of 4 (5 referring to the line width) lower than that of GERDA with pulse shape analysis. The amount of enriched material used in the GERDA measurement is 14.6 kg, only a factor of 1.34 larger than that used in the HEIDELBERG-MOSCOW experiment. The background model is oversimplified and not yet adequate. It is not shown that the lines of their background can be identified. GERDA has to continue the measurement further ～5 years, until they can responsibly present an understood background. The present half life limit presented by GERDA of T ₁ ^2/0v > 2.1 × 10²⁵ y (90% confidence level, i.e. 1.6ρ) is still lower than the half-life of T ₁ ^2/0v = 2.23 _?0.31 ^+0.44 × 10²⁵ y [1] determined in the HEIDELBERG-MOSCOW experiment.     

Spatial periodic forcing can displace patterns it is intended to control

Spatial periodic forcing of pattern-forming systems is an important, but lightly studied, method of controlling patterns. It can be used to control the amplitude and wave number of one-dimensional periodic patterns, to stabilize unstable patterns, and to induce them below instability onset. We show that, although in one spatial dimension the forcing acts to reinforce the patterns, in two dimensions it acts to destabilize or displace them by inducing two-dimensional rectangular and oblique patterns.     

Relevance of the weak equivalence principle and experiments to test it: Lessons from the past and improvements expected in space

Tests of the Weak Equivalence Principle (WEP) probe the foundations of physics. Ever since Galileo in the early 1600s, WEP tests have attracted some of the best experimentalists of any time. Progress has come in bursts, each stimulated by the introduction of a new technique: the torsion balance, signal modulation by Earth rotation, the rotating torsion balance. Tests for various materials in the field of the Earth and the Sun have found no violation to the level of about 1 part in 10¹³. A different technique, Lunar Laser Ranging (LLR), has reached comparable precision. Today, both laboratory tests and LLR have reached a point when improving by a factor of 10 is extremely hard. The promise of another quantum leap in precision rests on experiments performed in low Earth orbit. The Microscope satellite, launched in April 2016 and currently taking data, aims to test WEP in the field of Earth to ${10}^{?15}$, a 100-fold improvement possible thanks to a driving signal in orbit almost 500 times stronger than for torsion balances on ground. The ‘Galileo Galilei’ (GG) experiment, by combining the advantages of space with those of the rotating torsion balance, aims at a WEP test 100 times more precise than Microscope, to ${10}^{?17}$. A quantitative comparison of the key issues in the two experiments is presented, along with recent experimental measurements relevant for GG. Early results from Microscope, reported at a conference in March 2017, show measurement performance close to the expectations and confirm the key role of rotation with the advantage (unique to space) of rotating the whole spacecraft. Any non-null result from Microscope would be a major discovery and call for urgent confirmation; with 100 times better precision GG could settle the matter and provide a deeper probe of the foundations of physics.