Lifeboat Foundation

“I view string theory as the most promising way to quantize matter and gravity in a unified way. We need both quantum gravity and we need unification and a quantization of gravity. One of the reasons why string theory is promising is that there are no singularities associated with those singularities are the same type that they offer point particles.” — Robert Brandenberger.

In this thought-provoking conversation, my grad school mentor, Robert Brandenberger shares his unique perspective on various cosmological concepts. He challenges the notion of the fundamental nature of the Planck length, questioning its significance and delving into intriguing debates surrounding its importance in our understanding of the universe. He also addresses some eyebrow-raising claims made by Elon Musk about the limitations imposed by the Planck scale on the number of digits of pi.

Continue reading “Unseen Fluctuations: Challenging Inflation | Robert Brandenberger” »

Patreon: https://www.patreon.com/seanmcarroll.
Blog post with audio player, show notes, and transcript: https://www.preposterousuniverse.com/podcast/2023/07/31/245-…n-physics/

Physics is in crisis, what else is new? That’s what we hear in certain corners, anyway, usually pointed at “fundamental” physics of particles and fields. (Condensed matter and biophysics etc. are just fine.) In this solo podcast I ruminate on the unusual situation fundamental physics finds itself in, where we have a theoretical understanding that fits almost all the data, but which nobody believes to be the final answer. I talk about how we got here, and argue that it’s not really a “crisis” in any real sense. But there are ways I think the academic community could handle the problem better, especially by making more space for respectable but minority approaches to deep puzzles.

Continue reading “Mindscape 245 | Solo: The Crisis in Physics” »

“A place for everything and everything in its place”—making sense of order, or disorder, helps us understand nature. Animals tend to fit nicely into categories: Mammals, birds, reptiles, whatever an axolotl is, and more. Sorting also applies to materials: Insulator, semiconductor, conductor, and even superconductor. Where exactly a material lands in the hierarchy depends on a seemingly invisible interplay of electrons, atoms, and their surroundings.

Unlike animals, the boundaries are less sharp, and tweaking a material’s environment can force it to bounce between categories. For example, dialing down the temperature will turn some materials into superconductors. Snapping on a magnetic field might reverse this effect. Within a single category, different types of order, or phases, can emerge from the sea of particles.

Unfortunately, we can’t see this nanoscopic universe with our eyes, but scientists can use advanced imaging tools to visualize what’s going on. Every once in a while, they uncover unexpected and surprising behaviors.

Thermal field theory seeks to explain many-body dynamics at non-zero temperatures not considered in conventional quantum field theory.

The thermal field theory, as presented by Munshi G. Mustafa, bridges statistical mechanics and quantum field theory, simplifying the analysis of many-body systems and enhancing the understanding of high-energy collisions and early universe evolution.

Quantum field theory is a framework used by physicists to describe a wide range of phenomena in particle physics and is an effective tool to deal with complicated many-body problems or interacting systems.

There is a lot of speculation about the end of the universe. Humans love a good ending after all. We know that the universe started with the Big Bang and it has been going for almost 14 billion years. But how the curtain call of the cosmos occurs is not certain yet. There are, of course, hypothetical scenarios: the universe might continue to expand and cool down until it reaches absolute zero, or it might collapse back onto itself in the so-called Big Crunch. Among the alternatives to these two leading theories is “vacuum decay”, and it is spectacular – in an end-of-everything kind of way.

While the heat death hypothesis has the end slowly coming and the Big Crunch sees a reversal of the universe’s expansion at some point in the future, the vacuum decay requires that one spot of the universe suddenly transforms into something else. And that would be very bad news.

There is a field that spreads across the universe called the Higgs field. Interaction between this field and particles is what gives the particles mass. A quantum field is said to be in its vacuum state if it can’t lose any energy but we do not know if that’s true for the Higgs field, so it’s possible that the field is in a false vacuum at some point in the future. Picture the energy like a mountain. The lowest possible energy is a valley but as the field rolled down the slopes it might have encountered a small valley on the side of that mountain and got stuck there.

The Belle II cooperation project at the Japanese research center KEK is helping researchers from all over the world to hunt for new phenomena in particle physics. The international experiment has now reached a major milestone after a team successfully installed a new pixel detector in its final location in Japan.

The size of a soda can, the detector was developed in order to make out the signals coming from certain types of particle decays, that can shed light on the origin of the matter–antimatter asymmetry that has been observed in the universe. The installation ran without a hitch and is a key milestone in the evolution of the experiment and German–Japanese research collaboration.

Based at the SuperKEKB accelerator in Japan’s KEK research center, Belle II is an international collaborative project involving researchers from all over the world. The experiment aims to find answers to the many unresolved questions about the universe that are out there. To this end, the 1,200 or so members of the international Belle II collaboration are searching for signs of new phenomena in physics and unknown particles not covered by the established Standard Model of particle physics.

Rice University physicists have shown that immutable topological states, which are highly sought for quantum computing, can be entangled with other manipulable quantum states in some materials.

“The surprising thing we found is that in a particular kind of crystal lattice, where electrons become stuck, the strongly coupled behavior of electrons in d atomic orbitals actually act like the f orbital systems of some heavy fermions,” said Qimiao Si, co-author of a study about the research in Science Advances.

The unexpected find provides a bridge between subfields of condensed matter physics that have focused on dissimilar emergent properties of quantum materials. In topological materials, for example, patterns of quantum entanglement produce “protected,” immutable states that could be used for quantum computing and spintronics. In strongly correlated materials, the entanglement of billions upon billions of electrons gives rise to behaviors like unconventional superconductivity and the continual magnetic fluctuations in quantum spin liquids.

A collaboration of nuclear theorists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, Argonne National Laboratory, Temple University, Adam Mickiewicz University of Poland, and the University of Bonn, Germany, has used supercomputers to predict the spatial distributions of charges, momentum, and other properties of “up” and “down” quarks within protons. The results, just published in Physical Review D, revealed key differences in the characteristics of the up and down quarks.

“This work is the first to leverage a new theoretical approach to obtain a high-resolution map of quarks within a proton,” said Swagato Mukherjee of Brookhaven Lab’s nuclear theory group and a co-author on the paper. “Our calculations show that the up quark is more symmetrically distributed and spread over a smaller distance than the down quark. These differences imply that up and down quarks may make different contributions to the fundamental properties and structure of the proton, including its internal energy and spin.”

Co-author Martha Constantinou of Temple University noted, “Our calculations provide input for interpreting data from nuclear physics experiments exploring how quarks and the gluons that hold them together are distributed within the proton, giving rise to the proton’s overall properties.”

Newly released data taken using the Belle II experiment at KEK in Japan and the LHCb experiment at CERN in Switzerland show no sign of a possible anomaly that researchers think could provide a route to overturning the standard model of particle physics [1– 3].

According to the standard model, electrons, muons, and tau leptons should all behave identically when subjected to any of the fundamental forces of nature. Over a decade ago, researchers began questioning the validity of this assumption—known as lepton universality—when they observed high-energy particle decays that deviated from standard-model predictions. Specifically, the observations concerned the decay of B mesons into various leptons, with the experiments hinting that a few more tau leptons were being produced than expected. Excitement built among particle physicists, who hoped they were on the cusp of finding the long-sought standard-model violation that would uncover new physical phenomena. Hopes rose further as other experiments found hints of lepton-universality violations in the decay of B mesons into electrons and muons, but the signals remained too small to rule out experimental artifacts.

Then at the end of last year, hopes began to fade when the LHCb Collaboration released data for B-meson decays involving electrons and muons that exactly matched standard-model predictions [2, 3]. Now data from the Belle II Collaboration for a different B-meson decay involving electrons and muons dim those hopes further [1]. The study provides the most precise lepton-universality test yet in such decays. But researchers haven’t yet given up on leptons unlocking a door to new physics, says Belle II Collaboration member Henrik Junkerkalefeld of the University of Bonn, Germany. He notes that, although the results provide new constraints on the options for undiscovered physics, they don’t completely rule them all out.