Projecten ITFA 2015
De natuur is van ons allen. Neem je deel! Presentatie/coordinatie: Theo Nieuwenhuizen
Symmetry breaking Quantum-to-classical crossover Jasper van Wezel •
2nd year project "Spontaneous Symmetry Breaking”
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During this project you will study the theory of spontaneous symmetry breaking, and its applications in both classical and quantum physics. You will investigate the similarities and differences between a pencil balancing on its tip, a chair being localised below you, a magnet having a north pole, superconductors conducting electricity without resistance, and if time permits, the Higgs effect. [requires knowledge of quantum mechanics up to but not including perturbation theory]:
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3rd year project: "Simulating the quantum-to-classical crossover”
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This project will seek to simulate the dynamical evolution of a quantum system close to the quantum-to-classical crossover, within a particular model for this crossover. The model used is that of spontaneous unitarity breaking, which is a form of spontaneous symmetry breaking applied to quantum dynamics. The simulated dynamics will be relevant for the study of qubits in a noisy environment as well as for the interpretation of some questions in quantum foundations.
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Monte Carlo simulations in statistical physics Philippe Corboz
Bachelor project: Monte Carlo simulations of the 3-state Potts model in 2D The 3-state Potts model is a generalization of the well-known Ising model which is the simplest model of interacting spins on a lattice. Both models exhibit a continuous phase transition between an ordered phase at low temperature and disordered phase at high temperature. In this project the phase transition and the thermodynamic properties of the 3-state Potts model are studied by means of numerical Monte Carlo simulations. (Requirements: Knowledge in statistical physics and good programming skills).
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Bachelor project: Corner Transfer Matrix method applied to classical spin systems The partition function of a two-dimensional classical spin system with nearest-neighbor interactions can be represented as a network of rank-4 tensors. The corner-transfer matrix method is an efficient approach to contract this network (i.e. to compute the partition function). This method will be used to investigate the thermodynamic properties and phase transitions in classical spin systems. (Requirements: Knowledge in statistical physics and good programming skills).
Granular matter
2nd year projects
Density of vibrational modes of highly compressed harmonic sphere packings In this project the students will investigate numerically the statistics and geometric characteristics of low-energy excitations in highly compressed packings of soft harmonic spheres, which have been observed to mysteriously deviate from the Debye theory.
Density of vibrational modes of highly anisotropic solids In this project the students will investigate analytically how the density of states and mode structure of elastic solids is altered due to the presence of a high degree of anisotropy of their linear elastic moduli. Interestingly, this question can be related to the rapid divergence of the viscosity of dense non-Brownian suspensions close to jamming.
Theory of elastic moduli of colloidal fcc and hcp crystals In this project the students will apply a recently-proposed theory for the calculation of the free energy of colloidal systems close to their jamming point, and predict the values
Edan Lerner
Granular matter
bachelor projects
Emergence of singularities in contact-force distributions in isostatic packings of harmonic spheres In this project the student will investigate numerically the emergence of singularities in distributions of contact forces in isostastatic packings of hard spheres, by approaching the unjamming point from above in harmonic soft-sphere packings. Good programming skills are required for this project.
Dilatancy of nearly-jammed colloidal glasses under simple shear Until recently, it was commonly believed that colloidal glasses do not dilate under simple shear deformation. However, new theoretical predictions claim the opposite. In this project the student will validated or invalidated this prediction by an analytical and numerical investigation.
Finite-size scaling & spectral analysis of isostatic packings In this project the student will investigate analytically and numerically the geometric properties of isostatic packings of hard spheres, by finite-size scaling and spectral analyses.
Oscillatory compression of colloidal glass (reversibility and indeterminacy) It has been observed that oscillatory compression of soft spheres near their unjamming point leads eventually to reversibility in their dynamics. However, an open question remains, whether a similar phenomenon occurs in colloidal glasses as well. Good programming skills are essential for this project.
Edan Lerner
High energy physics •
Spontaneous symmetry breaking and the Higgs boson: (2nd year project)
Wouter Waalewijn
Spontaneous symmetry breaking plays a role in many different phenomena in particle physics. The recently discovered Higgs boson is responsible for breaking electroweak symmetry, and there is a direct connection between pions and chiral symmetry breaking. This project would involve learning about global and local symmetries, spontaneous symmetry breaking, Goldstone bosons and the Higgs mechanism.
CP violation in the Standard Model: (2nd year project) The breaking of charge conjugation and parity is essential to explain the asymmetry between matter and anti-matter in our universe. The goal would be to investigate these symmetries and their sources of breaking in the Standard Model. Specifically: the weak interactions, the CKM matrix and the QCD vacuum (strong CP problem).
The structure of jets at the LHC: (Bachelor thesis) Quarks and gluons produced at the Large Hadron Collider result in sprays of collimated energetic hadrons, called jets. The excellent performance of the detectors at the Large Hadron Collider has opened up the possibility to use the substructure of jets in the hunt for new physics. This project would focus on understanding the splitting picture that underlies parton showers, and exploiting it to analytically calculate properties of jets at leading logarithmic precision.
The effective field theory of physics beyond the Standard Model: (Bachelor thesis) Effective field theories provide a systematic approach to quantifying the effects of physics beyond the Standard Model. They allow one to relate constraints from measurements that probe very different scales, by taking into account the effect of the renormalization group evolution. The goal would be to learn the basics of effective field theories, which is an important tool in many modern areas of high energy physics, and study its ramifications in the search for physics beyond the Standard Model.
String Theory, Quantum Gravity and physical applications of Holography 3rd yr •
My research is centered around the study of Quantum Gravity in non trivial spacetimes. Holography is a tool discovered within String Theory that allows for the study of these problems by solving dual problems in Quantum Field Theory. Diego Hofman
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At the same time, interesting problems in strongly coupled Quantum Field Theory can be studied by solving classical equations of motion in General Relativity. (connections to Condensed Matter Physics, Mathematical Physics, Cosmology, Particle Physics, etc.) Bachelor Thesis proposal: I suggest the student to undertake the study of quantum mechanical systems that might have dilatation symmetry but no conformal symmetry. Some systems of this sort are exactly solvable. Their space of solutions could have more symmetries than expected and, as such, are interesting systems.
• Quantum description of light-matter interaction. 3rd yr The aim is to understand the quantization of electromagnetic field interacting with atoms. Next step would to apply it for describing physics of cavityand cirquit-QED setups and to other nano-optical systems.
Vladimir Gritsev
• Topological insulators. 3rd year After understanding the concept of Berry phase (and more generally, geometric phase), the aim of this project is to see how the topology enters the solid state physics through a new class of materials, the topological insulators.
String theorie, Zwarte gaten, Holografisch principe, Extra dimensies, Donkere Energie, Kosmologie, Inflatie • • • •
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2e-jaars projecten Jan-Pieter + Hawking straling en de informatie paradox van der Schaar - Basisbegrip van Hawking straling en haar consequenties + Kosmologische inflatie en de oorsprong van structuur - Wat is inflatie en hoe verklaart het de oorsprong van structuur in het heelal? + String theorie, zwaartekracht en extra dimensies - Basisbegrip string theorie: waarom bevat het zwaartekracht en extra dimensies? 3e-jaars projecten: + Kosmologische inflatie en het multiversum - Wat is het multiversum en hoe kan het gerealiseerd worden? + Kosmologische horizons: kwantum-verstrengeling en holografie - Hoe meet je kwantum-verstrengeling, wat is 'verstrengelings-entropie’ en wat is de mogelijke rol in een kosmologische context.? + Conforme stelsels in de algemene relativiteitstheorie en het equivalentie-principe In veel modellen, waaronder string theorie, vindt men extra scalaire velden die een speciale rol spelen in relatie tot zwaartekracht. Dit betekent ondermeer dat het equivalentie principe niet gerealiseerd is en het geeft aanleiding tot het bestaan van verschillende 'conforme stelsels'. Heeft dit mogelijk consequenties voor ons heelal?
Putting galaxies on the scale 2nd year: Het wegen van melkwegstelsels
Christoph Weniger
What do we know about the mass of the Milky Way and other galaxies? The students will work on various theoretical and observational techniques to estimate the masses of galaxies and galaxy clusters. Goal is to obtain a gravitational estimate for the total matter density in the Universe, and to compare this result with the density of ordinary ("baryonic") matter.
• Clusters – structure and formation
Fabio Zandanel •
2nd-year - Clusters of galaxies host very diffuse synchrotron radio emission which is though to be tied to structure formation processes. You will review the current knowledge on several multi-frequency scaling relations that tries to relate the synchrotron emission to the dynamical status of clusters.
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3rd-year - The Fermi satellite is continuously observing the gamma-ray sky between 30 MeV to 300 GeV. You will analyze the Fermi satellite data of a nearby galaxy cluster, Perseus, which contain two bright active galactic nuclei and try to obtain constraints on the possible underlying diffuse gamma-ray emission from structure formation process in the cluster.
3e jaar Symbols and Goncharov polylogarithms in quantum correcHons
For precise predicHons of LHC cross secHons, one must include quantum Eric correcHons to scaJering amplitudes. These correcHons oMen involve Laenen loop integrals that result in expressions with special funcHons such as polylogarithms. Recently a very interesHng mathemaHcal technology, based on a Hopf structure, and involving so-‐called symbol maps has been shown to lead to dramaHc simplificaHons of the results, by almost automaHcally finding simplifying relaHons between the polylogarithms. This project involves learning elementary aspects of loop integrals, special funcHons and the symbol map. Special aJenHon will be given to extracHng imaginary parts, which give the cross secHons. 3e jaar: Higgs compositeness Last summer the LHC experiments discovered a new boson, which may well be the Standard Model Higgs. Full verificaHon of this will sHll take some Hme. It could sHll be that the Higgs is a composite of a fermion-‐anH fermion pair. In this project we look at recent viable soluHons for this idea, from a general point of view.
Ketting hevelen (2e jaar) Veronderstel een lange soepele ketting in een potje. Als je het uiteinde van die ketting over de rand hangt, en het neerhangende is voldoende lang, zal de ketting uit het potje stromen. Het verrassende is dat de ketting niet strak over de rand stroomt, maar met een boog die veel hoger komt dan de rand. Een mooie demonstratie is te zien op http://www.youtube.com/watch?annotation_id=annotation_625777&feature=iv&src_vid=_dQJBBklpQQ&v=6ukMId5fIi0
waarvan hier een snapshot. De bedoeling van dit project is een goede verklaring te geven van dit verschijnsel, en een voorspelling van de vorm waarin de ketting het potje verlaat. Er zal alleen een boog ontstaan als de ketting in aanvang door de rand van het potje omhoog wordt geforceerd. Maar het is niet duidelijk of de hoogte van de uiteindelijke boog ook afhangt van de hoogte van de beker. De uitstroom doet denken aan de hevel werking van een vloeistof door een U-vormige buis. Die analogie suggereert dat ook een hevelbuis zou kunnen gaan zweven bij gebruik. Daar kunnen we ook aan gaan rekenen. En natuurlijk is dit project niet compleet zonder enkele eenvoudige experimenten(, waarbij Robert Spreeuw bereid is te helpen).
Bernard Nienhuis
2e en 3e jaar
• Quantum thermodynamica
Wat blijft er van thermodynamica over voor kleine systemen, gekoppeld aan een macroscopisch bad en werkbron?
• “Quantum” gedrag van dansende oliedruppels
Theo Nieuwenhuizen
Een bakje olie wat op-en-neer gaat, kan een druppel van die olie op zijn oppervlak laten “dansen”. Er blijken interferentie-effecten op te treden zoals in de quantum mechanica.
• Neutrino donkere materie – neutrino massa
Als donkere materie deels door neutrino’s komt, wat is dan hun massa ? Bestudeer de lenswerking van een cluster van melkwegstelsels.
• Stochastische electrodynamica
Komt quantum gedrag soms vanwege een stochastisch electromagnetisch veld, wat het quantum “vacuum” vormt ? Hoe ver kom je met die aanname ?
Quantum meetprobleem 2e jaar (ahum) en 3e jaar • Leerboeken: meting beschreven door postulaten Instorten van de golffunctie, Born regel • Een meetapparaat is ook een fysisch systeem • Kun je een quantummeting beschrijven door het meetapparaat te modeleren? • Meetprobleem: Kun je verklaren dat je bij een quantummeting een enkele waarde meet? • Wat is de minimale interpretatie van de QM?
Theo Nieuwenhuizen
