Month: September 2022

A WORLD IN A GRAIN OF SAND. “The two scalar modes Ψ and Φ, relevant for cosmological observations in the physical universe, play an important role in the gravity analogue for granular matter. We fo- cus on the effect of external stress perturbations on the changes in the analogue spatial geometry.” https://lnkd.in/dusKMKM View in LinkedIn

COSMOLOGY. “In the physical universe, the vector mode dies out fast due to the expanding spacetime. In the analogue gravity/cosmology situation addressed here, even though we are dealing with a contracting spacetime, we are at liberty to ignore the vector mode in the first place without altering the curl-free and non zero trace condition of χij.” https://lnkd.in/dusKMKM View in LinkedIn

EXTRAORDINARY LEADERSHIP. “New Zealand aims to create smoke-free generation. Proposals include making sale of cigarettes to anyone born after 2004 illegal. The plan will begin the final demise of tobacco products in this country.” I usually do not comment on politics, but this is different. https://lnkd.in/dNJBbAP View in LinkedIn

A wild garlic blossom, pure and relatively unscented. View in LinkedIn

COSMIC LENSING. “A further interesting aspect of this correspondence is the analogue lensing in a photo-elastic material. The physical measurable quantities in this scenario are the correlators of refractive index which depend on the central difference rather than an absolute measure.” https://lnkd.in/dusKMKM View in LinkedIn

VECTOR SUM. “The interplay between gravity (which is inherently attractive) and background space- time sets up the analogue contact forces, purely repulsive or attractive, frictional or frictionless. In our analogy it is not necessary to add any tensorial polarization field due to bound vector charges as in the VCT.” https://lnkd.in/dusKMKM View in LinkedIn

FLUIDS VS SOLIDS. “Analogue gravity in barotropic, in viscid fluids with acoustic perturbations is now well-understood both theoretically and observationally. In that case, the knowledge of the basic fluid mechanics equations (Euler-Navier-Stokes) for centuries provides a relative advantage over the case of granular matter where fundamental theoretical understanding is still being sought.” https://lnkd.in/dusKMKM View in LinkedIn

THE ISSUE OF FRAGILITY. “The incipient, preliminary and necessarily incomplete general relativistic analogy presented here falls short of describing an important feature of granular matter, namely fragility.” https://lnkd.in/dusKMKM View in LinkedIn

REPULSIVE FORCE. “Further, the attractive nature of gravity implies that a gravity analogue of granular matter may be deemed inadequate for describing microscopic granular repulsions.” https://lnkd.in/dusKMKM View in LinkedIn

FUDGE FACTOR. “If so, a partial remedy of this situation may emerge from introducing a cosmological constant into the analogy. An alternate mapping of the jamming state, especially shear jamming, may also emerge from considering expanding analogue spacetimes, rather than contracting ones as done here.” (Einstein’s “greatest mistake” was the cosmological constant). https://lnkd.in/dusKMKM View in LinkedIn