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Category: particle physics – Page 401

Why aren’t neutrinos adding up?

In the two decades since short-baseline neutrino anomalies were first discovered, scientists have come up with several guesses about what might cause discrepancies.

Of all the known elementary particles, neutrinos probably give physicists the most headaches.

These tiny fundamental bits of matter are the second most common particle in the universe yet are anything but ordinary. Since their discovery, they have taunted scientists with bizarre behaviors, some of which physicists have yet to comprehend.

One source of confusion has showed up in the results from short-distance neutrino experiments, in which neutrinos are measured after traveling somewhere between a few meters and a kilometer. When scientists measure neutrinos in these experiments, the results don’t always match their predictions. Sometimes there are too many of certain types of neutrinos, while in others there are too few.

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Building decarbonization: How electric heat pumps could help reduce emissions today and going forward

The electrification of heating systems could play a significant role in building decarbonization. Heat pumps are emerging as a solution.

Iranian scientists have demonstrated a multi-layer silicon nanoparticle (SNP) solar cell based on nanoparticles that are densely stacked inside a dielectric medium. They considered different SNP structures and configurations to tailor these particles as a p–n junction cell.

Ultra-thin silicon nanoparticle solar cell with 11% efficiency

“This is because SNPs are assumed to be the main absorber in the cell. Thus, any distance between them reduces the absorption of incident photons,” the group said.

They considered different SNP structures and configurations to tailor these particles as a p–n junction cell. They said this kind of cell could achieve a theoretical efficiency of around 11%.

Exceeding 100 percent quantum efficiency in the photocurrent of a hybrid inorganic-organic semiconductor

Tiny crystals, known as quantum dots, have enabled an international team to achieve a quantum efficiency exceeding 100 percent in the photocurrent generated in a hybrid inorganic-organic semiconductor.

Perovskites are exciting semiconductors for light-harvesting applications and have already shown some impressive performances in solar cells. But improvements in photo-conversion efficiency are necessary to take this technology to a broader market.

Light comes in packets of energy known as photons. When a semiconductor absorbs a photon, the is transferred to a negatively charged electron and its positively charged counterpart, known as a hole. An can sweep these particles in , thereby allowing a current to flow. This is the basic operation of a solar cell. It might sound simple, but optimizing the quantum efficiency, or getting as many from the incoming photons as possible, has been a long-standing goal.

Time is the increase of order, not disorder

The received view in physics is that the direction of time is provided by the second law of thermodynamics, according to which the passage of time is measured by ever-increasing disorder in the universe. This view, Julian Barbour argues, is wrong. If we reject Newton’s faulty assumptions about the existence of absolute space and time, Newtonian dynamics can be shown to provide a very different arrow of time. Its direction, according to this theory, is given by the increase in the complexity and order of a system of particles, exactly the opposite of what the received view about time suggests.

Two of the most established beliefs of contemporary cosmology are that the universe is expanding and that the direction of the arrow of time in the universe is defined by ever-increasing disorder (entropy), as described by the second law of thermodynamics. But both of these beliefs rest on shaky ground. In saying that the universe is expanding, physicists implicitly assume its size is measured by a rod that exists outside the universe, providing an absolute scale. It’s the last vestige of Newton’s absolute space and should have no place in modern cosmology. And in claiming that entropy is what gives time its arrow, physicists uncritically apply the laws of thermodynamics, originally discovered through the study of steam engines, to the universe as a whole. That too needs to be questioned.

Time min

Einstein and why the block universe is a mistake Read more In the absence of an absolute space and external measuring rods, size is always relative — relative to a measure of distance internal to the system. Starting from the simplest case, a triangle, what we find is that the internal measure of size produces a ratio which also happens to be related to a mathematical measure of complexity that intriguingly plays the central role in Newtonian universal gravitation. Applying these findings to the universe as a whole, we find that Newton’s theory of gravity, contrary to what physicists believe, contains within it an intrinsic arrow of time. This provides a strong hint that the direction of time is not defined by an increase in entropy, but by an increase in structure and complexity.

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