Sommerfeld Theory Colloquium (ASC)

The next generation of surveys, e.g. the Dark Energy Survey, PanSTARRS, LSST, Euclid and others, aim to study the nature of Dark Energy and alternatives.

The talk will discuss how the Dark Energy paradigm evolved over the past 20 years, and the cosmic probes which will help us to test it.

In particular the surveys rely on accurate of photometric redshifts for the determination of cosmological quantities such as Dark Energy parameters and neutrino masses.

The talk will describe photometric redshift methods and their impact on analysing galaxy clustering and weak lensing data and on the derived cosmological parameters.

The observed deviations from the laws of gravity of Newton and Einstein

in galaxies and clusters can logically speaking be either due to

the presence of unseen dark matter particles or due to a change in

the way gravity works in these situations. Until recently there was

little reason to doubt that general relativity correctly describes gravity

in all circumstances. In the past few year insights from black hole

physics and string theory have lead to a new theoretical framework in

which the gravitational laws are derived from the quantum entanglement

of the microscopic information that is underlying space-time.

An essential ingredient in the derivation is of the Einstein equations

is that the vacuum entanglement obeys an area law, a condition that

is known to hold in Anti-de Sitter space due to the work of Ryu

and Takayanagi. We will argue that in de Sitter space due to the

positive dark energy, that the microscopic entanglement entropy also

contains also a volume law contribution in addition to the area law.

This volume law contribution is related to the thermal properties of

de Sitter space and leads to a total entropy that precisely matches the

Bekenstein-Hawking formula for the cosmological horizon. We study

the effect of this extra contribution on the emergent laws of gravity,

and argue that it leads to a modification compared to Einstein gravity.

We provide evidence for the fact this modification explains the

observed phenomena in galaxies and clusters currently attributed to

dark matter.

Low-mass boson dark matter particles produced after the Big Bang

form a classical field and/or topological defects. Effects produced

by the interaction of ordinary matter with dark matter may be first

power in the underlying interaction strength rather than the second

power. This may give a big advantage, since the dark matter

interaction constant is extremely small. Limits on certain types of

dark matter have been improved up to 15 orders of magnitude. New

experiments are proposed.

In this talk I will discuss connections between the physics of complex

systems such as spin glasses and attempts to solve optimization

problems by ”Adiabatic Quantum Computing” (AQC), a version of ”Quantum Annealing” (QA). An optimization problem is one in which one has to minimize (or maximize) an energy function in which

there is competition between different terms so no single configuration

of the variables minimizes each term in the energy. In statistical

physics this competition is called ”frustration”. It leads to a complex

energy ”landscape” with many valleys separated by barriers, so

simple algorithms easily get trapped in local minima which have a

higher energy than the global minimum. Many problems in science,

and engineering are formulated as optimization problems. In quantum

annealing one tries to avoid being trapped in a local minimum by

adding quantum fluctuations so the system can tunnel to regions of

lower energy. The strength of the quantum fluctuations is gradually

reduced to zero during the annealing schedule. This method applies

to problems with binary variables, known as qubits in the quantum

case. There is considerable interest in AQC at present, in large part

because a company, D-Wave, has produced an actual device, the latest

version of which has about one thousand qubits. In addition,

there has been considerable theoretical work mainly using computer

simulations to see if there is a ”quantum speedup” compared with

analogous classical algorithms in which thermal, rather than quantum,

fluctuations are used to escape from local minima. In the talk

I will discuss difficulties in obtaining a quantum speedup due to (i)

(quantum) phase transitions that the system can undergo during the

annealing schedule, and (ii) the sensitivity of the state of the system

to the precise values of the interactions, i.e. chaos. A related chaotic

effect is that the state of the system can change dramatically with

small changes in the temperature (temperature-chaos), for thermal

annealing, and the strength of the quantum fluctuations, for quantum

annealing.

Quantum mechanics is important for determining the geometry of

spacetime. We will review the role of quantum fluctuations that determine

the large scale structure of the universe. In some model universes

we can give an alternative description of the physics in terms

of a theory of particles that lives on its boundary. This implies that

the geometry is an emergent property. Furthermore, entanglement

plays a crucial role in the emergence of geometry. Large amounts of

entanglement are conjectured to give rise to geometric connections,

or wormholes, between distant and non-interacting systems.

Do quantum many-body systems necessarily come to thermal equilibrium

after a long enough time evolution? The conventional wisdom

has long been that they do and that, in the process, any quantum

information encoded in the initial state is lost irretrievably. Thus the

dynamics of many-interacting particles becomes effectively classical.

But these ingrained notions of thermalization and ergodicity have

recently been called into question. In this talk I will discuss how

ergodicity can break down in disordered quantum systems through

the phenomenon of many-body localization. In contrast to thermalizing

fluids, quantum correlations can persist through time evolution

of the localized state even at high energy densities. Thus, investigating

the many-body localization transition offers a concrete route

to address fundamental unsolved questions concerning the boundary

between classical and quantum physics in the macroscopic world. I

will emphasize the important role that quantum entanglement plays

in current attempts to understand this fascinating dynamical phase

transition. Finally I will present recent progress in confronting the

emerging theoretical understanding of many-body localization with

experimental tests using systems of ultra-cold atoms.

Although the neutrino oscillations are well established phenomenon, new and unusual oscillation effects in matter are still emerging. I will describe three such effects which have applications to the solar, supernova and low energy atmospheric neutrinos: (i) Parametric resonance for neutrinos propagating in a flux of background neutrinos. (ii) Oscillation waves emitted from borders between layers in a multilayer medium, like in the Earth. (iii) The attenuation effect related to the energy uncertainty in oscillation setup.

Equivalence principle violation, deviations from the inverse-square

law of gravity, and long-range interactions between particle spins

o�er powerful tests of beyond-the-standard-model physics. Using a

torsion pendulum, a technique that dates to the 18th century, is still

the most sensitive way to search for these signatures of new physics.

I will talk about how the experiments are done and give an update on the current and future status of such torsion balance experiments in the Eot-Wash group.

We present Denario, an AI multi-agent system designed to be a scientific research assistant. Denario can perform many different tasks, such as generating ideas, checking the literature, developing research plans, writing and executing code, making plots, and writing a scientific paper. Denario is built as a modular system, and therefore, can perform either very specific tasks, such as generating an idea, or carrying out end-to-end scientific analysis using cmbagent as a deep-research backend. In this talk, we describe Denario and its modules in detail and illustrate its capabilities by presenting multiple AI-generated papers generated by it. These papers cover many scientific disciplines, such as astrophysics, biology, biophysics, biomedical informatics, chemistry, material science, mathematical physics, medicine, and planetary science. Denario can also perform research combining ideas from different disciplines, and we illustrate it by showing a paper that applies methods from quantum physics and machine learning with astrophysical data. We publicly release the code at https://github.com/AstroPilot-AI/Denario. A Denario demo can also be run directly on the web at https://huggingface.co/spaces/astropilot-ai/Denario, and the full app is deployed on the cloud.

Ultra-High-Energy Cosmic Rays (UHECRs) are particles with energies up to $3\times 10^20 eV$, originating from unknown sources and producing extensive air showers in Earth's atmosphere. In this talk, I will review the current status of UHECR observations, including the energy spectrum, mass composition, and anisotropy in their arrival directions. I will highlight how the knowledge of the Galactic Magnetic Field (GMF) of the Milky Way is crucial for identifying UHECR sources. Additionally, I will review recent models of the GMF. Finally, I will discuss the propagation of UHECRs from their sources through both intergalactic and galactic magnetic fields, and I will explore the prospects for future source identification.