Mechanisms and kinetics of exotic atom formation in hydrogen and helium

The current status of the theory of exotic atom formation in hydrogen and helium is briefly reviewed. The problems of the two-step mechanism of mu-atom formation in molecular hydrogen and of primary populations of hadronic metastable states in helium are discussed.     

MULTI-LAMBDA MATTER IN A CHIRAL HADRONIC MODEL

Multi-lambda matter is investigated in the framework of a chiral hadronic model. It is shown that multi-lambda matter consisting of {N,Λ} is a metastable state as the strangeness per baryon and the density of hadronic matter are varied. The effective lambda mass decreases as the baryon density increases, and remains larger than that of the nucleon.     

Dynamical diversity and metastability in a hindered granular column near jamming

Granular media jam into a panoply of metastable states. The way in which these states are achieved depends on the nature of local and global constraints on grains; here we investigate this issue by means of a non-equilibrium stochastic model of a hindered granular column near its jamming limit. Grains feel the constraints of grains above and below them differently, depending on their position. A rich phase diagram with four dynamical phases (ballistic, activated, logarithmic and glassy) is revealed. The statistics of the jamming time and of the metastable states reached as attractors of the zero-temperature dynamics is investigated in each of these phases. Of particular interest is the glassy phase, where intermittency and a strong deviation from Edwards' flatness are manifest.     

Metastable states,the adiabatic theorem and parity violating geometric phases I

A system of metastable plus unstable states is discussed. The mass matrix governing the time development of the system is supposed to vary slowly with time. The adiabatic limit for this case is studied and it is shown that only the metastable states obtain the analogs of the dynamical and geometrical phase factors familiar from stable states. Abelian and non-Abelian geometric phase factors for metastable states are defined.     

Dynamic Behavior of a Spin- 1 Ising Model. I. Relaxation of Order Parameters and the “Flatness” Property of Metastable States

The dynamic behavior of a spin-1 Ising system with arbitrary bilinear and biquadratic pair interactions is studied by using the path probability method, and approaches of the system toward the stable or metastable equilibrium states according to the ratio of interaction parameters and rate constants are presented. In particular, we investigate the relaxation of the order parameters for temperatures less than, equal to, and greater than the second-order and first-order phase transitions. From this investigation, the “flatness” property of metastable states is seen explicitly. We also show how a system freezes in a metastable state as well as how it escapes from one metastable state to the other.     

亚稳相的高压暴露

 很久以前,便有人指出,气态冷凝成固态时,要连续经历液相及各种高温相,才达到平衡结晶相。但是,液态及高温相往往需靠很大的冷却速度才能冻结下来,这在当时对绝大多数合金,是不可能的。近些年,随着超急冷等技术的进步,关于非晶等亚稳相得研究十分活跃。当超过一定临界冷却速度时,液态合金可固化为非晶态。虽然,亚稳结晶相较非晶应更容易冻结,但是,由于产生各种亚稳相所需的过冷条件各不相同,以及对冷却速度的选择不能是任意的,因此有时它们较非晶还难于形成。与液相凝固过程相似,非晶合金的晶化也服从构型最小重排原理,即在晶化完成之前,存在某些亚稳相变态阶段。但是,限于热力学上的不稳定性及动力学因素,在常压下这些亚稳相同样是难以发现的。作者根据对多种合金系的研究,提出高压暴露亚稳相的设想,并利用非晶等亚稳相的高压变态过程,将进行液态急冷时的速度控制方式,改为便于掌握的高压退火方式,来获得新亚稳相。本文对压力暴露亚稳相的原理和实践,加以论述。     

Metastable molecular fluid hydrogen at high pressures

Warm dense hydrogen is studied in the region of fluid–fluid phase transition within the framework of the density functional theory. We report a procedure of obtaining metastable states and calculate the equation of state. Metastable states are diagnosed by pair correlation functions and values of conductivity. We obtain a strong overlapping through the density of metastable and equilibrium branches of pressure isotherms. This indicates the plasma nature of the phase transition.     

Neutron star in the presence of strong magnetic field

Compact stars such as neutron stars (NS) can have either hadronic or exotic states like strange quark or colour superconducting matter. Stars can also have a quark core surrounded by hadronic matter, known as hybrid stars (HS). The HS is likely to have a mixed phase in between the hadron and the quark phases. Observational results suggest huge surface magnetic field in certain NS. Therefore, we study here the effect of strong magnetic field on the respective equation of states (EOS) of matter under extreme conditions. We further study the hadron–quark phase transition in the interiors of NS giving rise to HS in the presence of strong magnetic field. The hadronic matter EOS is described based on RMF theory and we include the effects of strong magnetic fields leading to Landau quantization of the charged particles. For quark phase, we use the simple Massachusetts Institute of Technology (MIT) bag model, assuming density-dependent bag pressure and magnetic field. The magnetic field strength increases from the surface to the centre of the star. We construct the intermediate mixed phase using Glendenning conjecture. The magnetic field softens the EOS of both the matter phases. We finally study, the mass–radius relationship for such types of mixed HS, calculating their maximum mass, and compare them with the recent observations of pulsar PSR J1614-2230, which is about 2 solarmass.     

Metastable states and their disintegration at pulse liquid heating and electrical explosion of conductors

The regularities of formation of metastable states and their disintegration under pulse liquid heating and electrical heating and explosion of conductors are studied. With a high energy flux density, the phase transitions occur with a high intensity of heat and mass fluxes, leading to spontaneous generation of a new phase and to phase explosion. The basic features of bubble-like disintegration in not uniformly superheated water and alcohol layers on the microheater are found. Regularities of matter disintegration with electrically exploded conductors are obtained. The metastable liquid disintegration is experimentally investigated for characteristic times of matter transfer to a metastable state of 1 to 4 μs; phase transitions during electric conductor explosion are studied at characteristic times of transfer to a metastable state to 200 ns. A common approach to describing the effects with radically different characteristic times of transfer of the matter to a metastable state is developed.     

A survey of heavy–heavy hadronic molecules

The spectrum of hadronic molecules composed of heavy–antiheavy charmed hadrons has been obtained in our previous work. The potentials are constants at the leading order, which are estimated from resonance saturation. The experimental candidates of hadronic molecules, say X(3872), Y(4260), three P_c states and P_cs(4459), fit the spectrum well. The success in describing the pattern of heavy–antiheavy hadronic molecules stimulates us to give more predictions for the heavy–heavy cases, which are less discussed in literature than the heavy–antiheavy ones. Given that the heavy–antiheavy hadronic molecules, several of which have strong experimental evidence, emerge from the dominant constant interaction from resonance saturation, we find that the existence of many heavy–heavy hadronic molecules is natural. Among these predicted heavy–heavy states we highlight the DD^* molecule and the ${D}^{(* )}{{\rm{\Sigma }}}_{c}^{(* )}$ molecules, which are the partners of the famous X(3872) and P_c states. Quite recently, LHCb collaboration reported a doubly charmed tetraquark state, T_cc, which is in line with our results for the DD^* molecule. With the first experimental signal of this new kind of exotic states, the upcoming update of the LHCb experiment as well as other experiments will provide more chances of observing the heavy–heavy hadronic molecules.     

Structure of phase change materials for data storage

Phase change materials based on chalcogenide alloys play an important role in optical and electrical memory devices. Both applications rely on the reversible phase transition of these alloys between amorphous and metastable cubic states. However, their atomic arrangements are not yet clear, which results in the unknown phase change mechanism of the utilization. Here using ab initio calculations we have determined the atomic arrangements. The results show that the metastable structure consists of special repeated units possessing rocksalt symmetry, whereas the so-called vacancy positions are highly ordered and layered and just result from the cubic symmetry. Finally, the fast and reversible phase change comes from the intrinsic similarity in the structures of the amorphous and metastable states.     

亚稳态fcc-Mn薄膜的生长及其同步辐射光电子能谱研究

报道亚稳态fcc-Mn薄膜在衬底温度为400K的GaAs(001)表面成功外延的结果.进而利用同步辐射光电子能谱研究该fcc-Mn薄膜随厚度变化的过程.从实验上得到fcc-Mn占有态的电子态密度分布,比较分析亚稳态的fcc-Mn相与热力学稳定的a-Mn相之间电子结构的显著差别,并给出可能的机制. 关键词：     

Influence of hadronic hard core radius on detonations and deflagrations in quark matter

The parameters for deflagration and detonations transitions between baryon-rich quark matter and hadronic matter are calculated at high densities and low temperatures. The equation of state of hadronic matter takes into account the hard core repulsion character of nuclear forces and the bag pressure is included in the quark phase. The transition is considered first directly from the quark phase to the hadronic phase. It is found that the velocity of the front separating the quark and nuclear phases as well as the energy flux are substantially larger than in the case where no hard core repulsion is taken into account. Most of the calculated quantities are only weakly dependent on the temperature in the region considered. The transitions from the quark phase to the mixed phase and from the mixed phase to the hadronic phase are also considered. No realistic solutions are found for the case where the temperature remains zero throughout the transition. At small temperatures and high densities solutions are obtained where the transition involves only minimal superheating. The energy flux for such a transition is small.     

Quantum mechanical look at the radioactive-like decay of metastable dark energy

We derive the Shafieloo, Hazra, Sahni and Starobinsky (SHSS) phenomenological formula for the radioactive-like decay of metastable dark energy directly from the principles of quantum mechanics. To this aim we use the Fock–Krylov theory of quantum unstable states. We obtain deeper insight on the decay process as having three basic phases: the phase of radioactive decay, the next phase of damping oscillations, and finally the phase of power-law decay. We consider the cosmological model with matter and dark energy in the form of decaying metastable dark energy and study its dynamics in the framework of non-conservative cosmology with an interacting term determined by the running cosmological parameter. We study the cosmological implications of metastable dark energy and estimate the characteristic time of ending of the radioactive-like decay epoch to be \(2.2\times 10^4\) of the present age of the Universe. We also confront the model with astronomical data which show that the model is in good agreement with the observations. Our general conclusion is that we are living in the epoch of the radioactive-like decay of metastable dark energy which is a relict of the quantum age of the Universe.     

Quantum reflection and dwell times of metastable states

The concept of phase and dwell times used in tunneling is extended to quantum collisions to derive a relation between the phase and dwell time delays in scattering. This relation can be used to remove the near threshold s-wave singularities in the Wigner-Eisenbud delay times and amounts to an extension of the concept of quantum reflection to strong interactions. Dwell time delay emerges as the quantity which gives the correct behavior of the density of states of a metastable state at all energies. This fact is demonstrated by investigating some recently found metastable states of mesic nuclei.     

Transverse momentum dependence of the e/π ratio and the decay of continuum vector states into di-leptons

The recently observed rise of the e/π ratio at small transverse momentum in pp collisions can be understood in a model with continuum hadronic vector states which decay into di-leptons. The mass and momentum distribution of the continuum hadronic states—which we derive from the distribution of produced quarks—is consistent with the distribution of hadronic clusters as determined from multi hadron correlation studies.     

A phenomenological theory of metastable states in disordered Ising magnets

A mechanism of the formation of an exponentially large number of metastable states in magnetic phases of disordered Ising magnets as a result of condensation of fractal delocalized modes near the localization threshold is suggested. The thermodynamic properties of metastable states are studied in the effective-field approximation in the vicinity of transitions in magnets with zero uniform magnetization in the ground state such as dilute antiferromagnets, spin glasses, and dilute ferromagnets with dipole interaction. These properties are shown to determine the parameters of nonequilibrium processes in the glassy phase, namely, the shape of the hysteresis loop, the thermodynamic values in field-cooled and zero-field-cooled regimes, and the thermoremanent and isothermal remanent magnetization values.     

Properties of hadron states containing a condensed phase of quark-antiquark excitations

We analyze how one-particle states can arise in a field theory of (three) quark triplets with current-current interactions which does not produce asymptotic quark states.A condensed phase of quark-antiquark pairs resembling the corresponding phase in a superconductor is responsible for the lack of stable states in the sectors with triality different from zero, provided that stable one-particle states indeed exist in the triality zero sectors, corresponding to stable configurations of valence quarks in the presence ofthe condensed phase.The precise dynamics of valence quarks is beyond the scope of the present model which is meant to illustrate a mechanism which prevents the basic quanta of the underlying fields to become asymptotically isolated and still eventually generates stable states in the hadronic sectors without inconsistencies.     

Covariant Hamiltonian dynamics with negative-energy states

A relativistic quantum mechanics is studied for bound hadronic systems in the framework of the point form relativistic Hamiltonian dynamics. Negative-energy states are introduced taking into account the restrictions imposed by a correct definition of the Poincaré group generators. We obtain nonpathological, manifestly covariant wave equations that dynamically contain the contributions of the negative-energy states. Auxiliary negative-energy states are also introduced, specially for studying the interactions of the hadronic systems with external probes.