Hello Cat
You said no universe.
Please define the Universe.
Hello Cat
That's so true if you are limited in information.
Relatively speaking.
The Universe is what it is.
We are limited in our information.
The Universe is all.. The deeper we look, the more we find. <Yes>
A key insight of Einstein's theory of the photoelectric effect is that a minimum energy is required for photoexcited electrons to escape from a material. For the past century it has been assumed that photoexcited electrons of lower energies make no contribution to the photoemission spectrum. Here we demonstrate the conceptual possibility that the energy of these 'failed' photoelectrons-primary or secondary-can be partially recycled to generate new 'tertiary' electrons of energy sufficient to escape. Such a 'recycling' step goes beyond the traditional three steps of the photoemission process (excitation, transport, and escape), and, as we illustrate, it can be realized through a novel Auger mechanism that involves three distinct minority electronic states in the material. We develop a phenomenological three-band model to treat this mechanism within a revised four-step framework for photoemission, which contains robust features of linewidth narrowing and population inversion under strong excitation, reminiscent of the lasing phenomena. We show that the conditions for this recycling mechanism are likely satisfied in many quantum materials with multiple flat bands properly located away from the Fermi level, and elaborate on the representative case of SrTiO3 among other promising candidates. We further discuss how this mechanism can explain the recent observation of anomalous intense coherent photoemission from a SrTiO3 surface, and predict its manifestations in related experiments, including the 'forbidden' case of photoemission with photon energies lower than the work function. Our study calls for paradigm shifts across a range of fundamental and applied research fields, especially in the areas of photoemission, photocathodes, and flat-band materials.
We know we cannot create or destroy matter.
So, how does matter recycle and rejuvenate?
The understanding will explain how the universe works.
We know we cannot create or destroy matter.
Energy can be converted into matter. This concept is described by Einstein's famous equation E=mc², which demonstrates that energy (E) and mass (m), the matter equivalent, are interchangeable, with 'c' being the speed of light. Scientists have demonstrated this through pair production, where a high-energy photon can be converted into a particle and its antiparticle (e.g., an electron and a positron).
[Submitted on 24 May 2025]Our construction is explicitly demonstrated for the perfect population transfer in the two-level system and the cyclic population transfer in the three-level system.
Conventional manipulations over quantum system, e.g., coherent population trapping and unidirectional transfer, focus on the Hamiltonian engineering while regarding the system's manifold geometry and constraint equation as secondary causes. Here we treat them on equal footing in controlling a finite-dimensional quantum system under a non-Hermitian Hamiltonian, which is inspired by the d'Alembert's principle for the active force, the constraint force, and the inertial force. The non-Hermitian Hamiltonian could be triangularized in a constraint picture spanned by a set of completed and orthonormal basis states, that is found to be a sufficient condition to construct at least one universal nonadiabatic passage in both bra and ket spaces. The passage ends up with a desired target state that is automatically normalized with no artificial normalization used in the existing treatments for non-Hermitian quantum systems. Our construction is explicitly demonstrated for the perfect population transfer in the two-level system and the cyclic population transfer in the three-level system. This theory substantially generalizes our framework of universal quantum control to the regime of non-Hermitian quantum mechanics.
Our findings reveal the existence of bouncing and cyclic solutions, regions where energy conditions are violated, and scenarios of accelerated expansion.
We investigate the cosmological dynamics induced by nonlinear electrodynamics (NLED) in a homogeneous and isotropic universe, focusing on the role of primordial electromagnetic fields with random spatial orientations. Building upon a generalization of the Tolman-Ehrenfest averaging procedure, we derive a modified energy-momentum tensor consistent with FLRW symmetry, incorporating the influence of the dual invariant G and its statistical contributions. A specific NLED model with quatratic corrections to Maxwell's Lagrangian is considered, giving rise to what we define as quasi-magnetic universe (qMU), interpolating between purely magnetic and statistically null field configurations. We analyze the resulting cosmological dynamics through qualitative methods. By casting the equations into autonomous dynamical systems, we identify the equilibrium points, determine their stability, and study the behavior of solutions under various spatial curvatures. Our findings reveal the existence of bouncing and cyclic solutions, regions where energy conditions are violated, and scenarios of accelerated expansion. Special attention is given to two limiting cases: the Magnetic Universe (MU) and the Statistical Null Universe (SNU), both of which exhibit qualitatively distinct phase portraits and energy-condition behavior. This work provides a comprehensive framework for understanding the influence of nonlinear electromagnetic fields in the early universe and opens avenues for exploring their observational consequences.