Fatigue and collapse of cyclically bent strip of amorphous solid

Fatigue caused by cyclic bending of a piece of material, resulting in its mechanical failure, is a phenomenon that had been studied for ages by engineers and physicists alike. In this Letter we study such fatigue in a strip of athermal amorphous solid. On the basis of atomistic simulations we conclude that the crucial quantity to focus on is the accumulated damage. Al- though this quantity exhibits large sample-to-sample fluctuations, its dependence on the loading determines the statistics of the number of cycles to failure. Thus we can provide a scaling theory for the Wo ̈hler plots of mean number of cycles for failure as a function of the loading amplitude.

Anti-gravity technology by non-positive equivalent mass revealing UFO flying secrets

In this paper, a novel kind of anti-gravity technology by non-positive equivalent mass of aircraft is presented to try to reveal UFO flying secrets. Starting with a two-degree-of-freedom system, it is found that the system could produce an infinite acceleration under the condition of zero dynamic equivalent mass[1], and also provide a movement opposite to the direction of the external force under the negative equivalent mass[2]. These two cases with non-positive equivalent mass[3] could both be regarded as a novel kind of anti-gravity technology[4,5], which is also verified by a designed dynamic simulation experiment. For any aircraft that can be regarded as a multi-degree-of-freedom system driven by engine or other external forces[6], the non-positive equivalent mass could be designed out once the external input including gravity and engine exciting forces is known[7]. Thus the anti-gravity technology for any aircraft could be realized, which could also be extended to matters related to flight, such as space ships, missiles, airplanes, etc[8].

Resonating delay equation

We propose here a delay differential equation that exhibits a new type of resonating oscillatory dynamics. The oscillatory transient dynamics appear and disappear as the delay is increased between zero to asymptotically large delay. The optimal height of the power spectrum of the dynamical trajectory is observed with the suitably tuned delay. This resonant behavior contrasts itself against the general behaviors where an increase of delay parameter leads to the persistence of oscillations or more complex dynamics.

Liquid-crystal metasurfaces: Self-assembly for versatile optical functionality

Liquid crystals subjected to modulated surface alignment assemble into metasurface-type structures capable of various flat-optical functionalities, including light diffraction and focusing, deflection and splitting. Remaining in a fluid phase, they are susceptible to external stimuli, and, in particular, can be efficiently controled by low voltages. We overview the existing approaches to the design and fabrication of liquid-crystal metasurfaces, highlight their realized optical functions and discuss the applied potential in emerging photonic devices.

Hole probability for non-interacting fermions in a d-dimensional trap

The hole probability, i.e., the probability that a region is void of particles, is a benchmark of correlations in many body systems. We compute analytically this probability P (R) for a sphere of radius R in the case of N noninteracting fermions in their ground state in a d-dimensional trapping potential. Using a connection to the Laguerre-Wishart ensembles of random matrices, we show that, for large N and in the bulk of the Fermi gas, P (R) is described by a universal scaling function of kF R, for which we obtain an exact formula (kF being the local Fermi wave-vector). It exhibits a super exponential tail P (R) / e-κd(kF R)d+1 where κdis a universal amplitude, in good agreement with existing numerical simulations. When R is of the order of the radius of the Fermi gas, the hole probability is described by a large deviation form which is not universal and which we compute exactly for the harmonic potential. Similar results also hold in momentum space.

Thermoelectric performance of MoSi(2)As(4) monolayer

Thermoelectric performance of MoSi2As4 monolayer is investigated using density functional theory combined with Boltzmann transport theoy. The maximal power factors of n- and p-type by PBE (HSE06) functional are 7.73 (48.31) and 32.84 (30.50) mW m-1 K-2 at the temperature of 1200 K, respectively. The lattice thermal conductivity is less than 30 W m-1 K-1 above 800 K. The thermoelectric figure of merit can reach 0.33 (0.58) and 0.90 (0.81) using PBE (HSE06) functional for n- and p-type under appropriate carrier concentration at 1200K, respectively. Thus, the p-type MoSi2As4 monolayer is predicted to be a potential candidate for high-temperature thermoelectric applications.

Scanning-probe and information-concealing machine learning intermediate hexatic phase and critical scaling of solid-hexatic phase transition in deformable particles

We investigate the two-dimensional melting of deformable polymeric particles with multi-body interactions described by the Voronoi model. We report machine learning evidence for the existence of the intermediate hexatic phase in this system, and extract the critical exponent $\nu\approx0.65$ for the divergence of the correlation length of the associated solid-hexatic phase transition. Moreover, we clarify the discontinuous nature of the hexatic-liquid phase transition in this system. These findings are achieved by directly analyzing system's spatial configurations with two generic machine learning approaches developed in this work, dubbed ``scanning-probe'' via which the possible existence of intermediate phases can be efficiently detected, and ``information-concealing'' via which the critical scaling of the correlation length in the vicinity of generic continuous phase transition can be extracted. Our work provides new physical insights into the fundamental nature of the two-dimensional melting of deformable particles, and establishes a new type of generic toolbox to investigate fundamental properties of phase transitions in various complex systems.

A thermodynamic origin for the Cohen-Kaplan-Nelson bound

The Cohen-Kaplan-Nelson bound is imposed on the grounds of logical consistency (with classical General Relativity) upon local quantum field theories. This paper puts the bound into the context of a thermodynamic principle applicable to a field with a particular equation of state in an expanding universe. This is achieved without overtly appealing to either a decreasing density of states or a minimum coupling requirement, though they might still be consistent with the results described. We do so by defining an appropriate Helmholtz free energy which when extremized relative to a key parameter (the Hubble radius L) provides a scaling formula for the entropy with the Hubble radius (an exponent r used in the text). We deduce that the CKN bound is one possible solution to this extremization problem (with r=3/2), but there are others consistent with r=2. The paper establishes that the holographic principle applied to cosmology is consistent with minimizing the free energy of the universe in the canonical ensemble, upon the assumption that the ultraviolet cutoff is a function of the causal horizon scale.

Improved gravity model for identifying the influential nodes

Identifying the influential nodes in network is essential for network dynamic analysis. In this letter, inspired by the gravity model, we present an improved gravity model (EDGM) to identify the influential nodes in network through the effective distance. Firstly, we calculate the degree of nodes. Then we construct the effective distance combined with the interaction frequency between nodes, so as to establish the effective distance gravity model. Comparing with the susceptible-infected model, the results show that the Kendall' s $\tau$ correlation coefficient of EDGM could enhanced by 2.36\% for the gravity model. Compared with other methods, the Kendall' s $\tau$ correlation coefficient of EDGM could enhanced by 11.55%, 17.29%, 7.17% and 10.00% for the degree centrality, betweenness centrality, eigenvector centrality, and PageRank respectively. The results show that the improved gravity model could effectively identify the influential nodes in network.

Geometrical aspects of hypermagnetic field interactions

We investigate the role of a dynamical torsion field coming from a geometrical non Riemannian model. This model is reminiscent of a generalized Born-Infeld theory and the torsion plays a fundamental role trough its Hodge dual: the pseudovector h_{μ}. This h_{μ} contains axion, Kalb-Ramond 2-form and physical observables of macroscopic character. An emergent interaction Lagrangian arises from the model and it is compared with a superstring inspired one from [8] pulling out several important consequences in favor of our proposal, as the possibility of establishing a clear connection between the change of CMB polarization plane and the anomalous current n_{chiral}.