Undergraduate colloquia

Date: 15 November 2023 at 12:00 (GMT)
Location: Blackett Lecture Theatre 1

Talk 1 Title: From SUEP to nuts: A full CMS search for Soft Unclustered Energy Patterns
Speaker: Pieter Van Steenweghen
Abstract: After years of unfruitful Beyond Standard Model searches targeting high-momentum final state particles at the Large Hadron Collider (LHC), there is a motivation to look for unconventional but experimentally challenging low-momentum final states. These low-energetic collider signatures might have evaded past LHC constraints, leaving a substantial previously unprobed phase space. One interesting case are Soft Unclustered Energy Patterns (SUEP), which consist of a large number of low-energetic spherically distributed final state particles. This SUEP signature, not found in SM processes, naturally arises from strongly coupled hidden valley models which are well-motivated DM candidates. This presentation provides a full overview of the first dedicated search for SUEPs at CMS, highlighting the cuts and tricks used to distinguish SUEP events from an overwhelming QCD background. This talk might be especially useful for undergraduates considering a research project or thesis in High Energy Physics.

Talk 2 Title: Obtaining reliable conductivity measurements in high resistivity semiconductor samples
Speaker: Emma Horgan
Abstract: Halide perovskites are emerging semiconductors which have attracted a lot of research interest in recent years due to  their possible advantages for use in solar cells, along with other applications. However, achieving reliable conductivity measurements of these materials is challenging due to their high resistance, on the GΩ to TΩ order of magnitude. The aim of my project was to construct an experimental setup which would give reliable conductivity measurements, which can then be used along with hall effect measurements to determine important parameters of the samples, such as the carrier mobility and carrier density.

Date: 6 December 2023 at 12:00 (GMT)
Location: Blackett Lecture Theatre 1

Talk 1 Title: Researching the Stability of Binary Star systems. 
Speaker: Wadoud Charbak
Abstract: This presentation highlights the journey and results of my UROP. Using REBOUND, a python based N-Body Integrator, I created a wide variety of simulations mainly focusing on two aspects: checking the stability of real systems by implementing information from the NASA Exoplanet archive and testing the limits of stability of a binary star systems using a system of two sun-like stars and a massless test particle. My results for the first part indicate that the majority of the star systems I simulated were stable in the long term. My results for the second part generated a table of different stability limits including a stark difference between prograde and retrograde orbits. 

Talk 2 Title: Over the Horizon Radars: The Physics of HF Propagation
Speaker: Daniel Somerville Roberts
Abstract: High Frequency (HF) electromagnetic waves are refracted by the ionosphere and can be reflected back towards the earth. This allows for beyond line-of-sight (BLOS) communication and is especially useful for military radars – however it is very susceptible to space weather and ionospheric conditions. This talk explains the science of HF propagation and ionospheric raytracing including the Appleton-Hartree formula, Haselgrove’s equations, and computational methods. We also discuss issues such as Faraday rotation and multipath and their effects on BLOS communication.

Date: 13 December 2023 at 12:00 (GMT)
Location: Blackett Lecture Theatre 1

Talk 1 Title: An initio density functional theory for nuclear systems
Speaker: Jean Luo
Abstract: Density functional theory (DFT) is a microscopic theory to describe quantum many-body problem, which provides a powerful computational method to simplify the unsolvable problem of N-body wavefunctions into a local density distribution for only one particle. Thus, DFT is currently known as the only viable theoretical method to describe large nuclear systems of A¬10^2. In recent years, DFT has become even more powerful thanks to the development of the functional renormalisation group aided DFT (FRG-DFT) formalism: the application of the functional renormalisation group (FRG), a vital tool for quantum field theory, to DFT. This project aims to study the behaviours of energy states of electron gas to a previously unreachable precision by considering their dependency on density gradient, which is based on a novel expansion method of the vertex function.

Talk 2 Title: Simulating the dynamics of a non-adiabatically driven transmon
Speaker: Vamsi Sridharbabu
Abstract: In superconducting quantum computing, a transmon qubit is type of charge qubit with a reduced sensitivity to charge noise by reducing the charge dispersion exponentially. However, this also reduces the anharmonicity of the transmon which allows higher level transitions due to resonant driving i.e. the transmon is now an anharmonic oscillator rather than a qubit. The aim of my project was to understand this response of the transmon with a non-adiabatically driven Josephson energy in the charge basis to shift the transmon from the transmon regime to the charging regime. The instantaneous change in the Hamiltonian of the transmon induced an periodic response in probability of the state of the transmon in the charging regime. Pulsing back into the transmon regime caused the probability to become constant, with dependence on the overall pulse width and pulse depth. This was used to further determine whether an effective pulsing sequence could be designed with the equipment available within the Quantum Science and Device Facility (QSDF) for performing single-"qubit" measurements. The interaction of the transmon with the environment were considered, but were not implemented for this simulation.

Date: 24 January 2024 at 12:00 (GMT)
Location: Blackett Lecture Theatre 1

Talk 1 Title: Checking the Semiclassical Limit of Quantum Gravity
Speaker: Roger Liu
Abstract: During the development of Loop Quantum Cosmology, numerous models predict the evolution of the universe. However, solving the propagation operators exactly often proves exceedingly complex. Consequently, Gaussian states are frequently employed as coherent states. This choice, though common, lacks justification, as there exist instances where Gaussian states exhibit instability. This project employs a 'quantum speed limit' check, as detailed in [https://arxiv.org/abs/2112.01597], to systematically assess the suitability of coherent states. The results reveal that Gaussian states successfully meet the criteria for the harmonic oscillator and 'improved dynamics,' while they predictably fail to satisfy the requirements for the anharmonic oscillator. This study extends its investigation to include additional examples of loop quantum gravity, further refining our understanding of these fundamental concepts.

Talk 2 Title: Computational Exploration of the Adiabatic Fermi Acceleration of Quantum Particles
Speaker: Yuvraj Dhunna
Abstract: Consider a cyclical process where the parameters of a Hamiltonian are changed adiabatically, an arbitrary perturbation is made, and finally the system is returned to its original Hamiltonian. It is expected that the energy of a particle described by the Schrodinger equation with such a Hamiltonian will increase, on average, exponentially over many cycles. Computational evidence is provided for this phenomenon and specific cases are explored.

Date: 21 February 2024 at 12:00 (GMT)
Location: Blackett Lecture Theatre 1

Talk 1 Title: Developing Fibre Optic Diagnostics for Pulsed Power
Speakers: Alexander Gavrishev and Eunju Moon
Abstract: Fibre optic sensors for pulsed power applications have several key advantages over the traditionally used technologies. Amongst them, fibre optic current sensors (FOCSs) are well understood and widely used in both industry and research, prized for their resilience against electromagnetic noise and their self-integrating nature. Our work has combined improvements in the design and analysis of polarimetric FOCSs to demonstrate that in pulsed power applications a reasonably high accuracy can be achieved without resorting to much more complicated and expensive layouts. Further explorative work by us has investigated a possible design of a fibre optic voltage sensor, which could be used where traditional technology has restricted such measurements within pulsed power machines, such as in First Light Fusion’s M3 and Cepage machines.

Talk 2 Title: Launching Helicon Waves in a Toroidal Plasma
Speaker: Patrick Quigley
Abstract: As a promising method for current drive in tokamaks, helicon waves are generating growing interest in the fusion community with helicon wave systems under development on tokamaks across the globe. However, despite being discovered in the 70s, much of the underlying physics behind helicon waves is still under scientific debate. To address the need for a deeper understanding of the fundamental physics at play, in 2023 an unprecedented helicon wave system has been installed on the TORoidal Plasma EXperiment (TORPEX). In this talk the first results from the new magnetic flux probe and unique resonant helicon antenna are presented.

Date: 2 November 2022 at 12:00 (BST)
Location: Blackett Lecture Theatre 1
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Talk 1 Title: Improved Design of a Pulsed Field Magnet
Speakers: Christine Wang and William Nguyen
Abstract: Imperial College London plasma group has Helmholtz coils manufactured for a pulse field magnet set-up powered by a discharge capacitor bank. Although generating up to 20 T should be possible due to the capacitor's bank capacitance of 3330 and its maximum voltage of 2800 V, the magnet's practical limits have not been tested. It is crucial to test whether the maximum B-field obtained agrees with the theory. Another issue is whether the magnet can withstand the sizeable magnetic pressure when high voltage is applied. Extrapolating the magnet's response to low continuous current led to an expected B-field of 8.3 ± 0.1 T in the discharge circuit. This result disagrees with the measured B-field from the 1110 V discharge (maximum voltage without damaging the magnet), 7.0 ± 0.3 T. This disparity was explained in terms of the B-dot probe construction and the impedance mismatch. Based on this result, a compromise design was proposed to improve the magnet and reach the target goal of 20 T. Implementing these changes would open up the possibility of performing plasma confinement and diagnostics, which are crucial in laser-plasma research. 

Talk 2 Title: Hunt Down the Minimum: An Introduction to Quantum Annealing
Speaker: Ivan Shalashilin
Abstract: Consider a map of cities, with roads connected between them: what would be the shortest path that visits each city? Now suppose we have a portfolio of shares: how do we choose the best assets that maximise profits 10 years in the future?

What do these optimisation problems have in common? They cannot be solved analytically, that is, with pen and paper and an equation trying to solve for x. Computational methods that are quite taxing are required.

However, quantum computing provides an alternative method of finding the best solution, namely quantum annealing (QA). The computational architecture of QA is employed by companies such as Google AI and D-Wave, with the potential to provide an exponential speedup in comparison to classical algorithms.

In this talk, we will investigate a particular application of QA in the context of the Weighted Max Independent Set problem, and how the presence of a third parameter can help speed up the QA process.

I advise a little bit of knowledge on eigenvalue problems a priori to make the talk easier to follow!

Date: 7 December 2022 at 12:00 (GMT)
Location: Blackett Lecture Theatre 1
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Talk 1 Title: Investigating DUNE's Ability to Detect Neutrinos Coincident with Gravitational Waves and their Expected Energy Spectra
Speaker: Trinity Stenhouse
Abstract: The Deep Underground Neutrino Experiment (DUNE) will have the ability to detect astrophysical neutrinos from various events including supernovae and mergers. Some of these events are also expected to emit gravitational waves (GWs), and therefore we have the potential to observe neutrinos and GWs coincident with each other. This would allow us to form a more complete picture of these important astrophysical events, which we hope will lead to valuable insights into the formation of celestial bodies, and the formation of our universe as a whole. 

Talk 2 Title: Probing Quark Gluon Plasma using B mesons - Measurement of B+ and Bs meson production in pp collisions at 5 TeV with CMS at the LHC
Speaker: Jean Luo
Abstract: Quark gluon plasma (QGP) is a very exotic state of matter, in which quark and gluons become free instead of being bound within hadrons. This state of matter is believed to have existed just after the Big Bang within a few microseconds. At the LHC, droplets of QGP can be reproduced by ultrarelativistic heavy ion collisions (URHICs) and detected by the Compact Muon Solenoid (CMS) detector. Our work aims to study how the presence of QGP affects the hadronisation process by calculating the production cross section in pp collisions, which serve as a comparison of heavy ion collisions in the case without the production of QGP.

Date: 8 February 2023 at 12:00 (GMT)
Location: Blackett Lecture Theatre 1
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Talk 1 Title: Inquiring About the Resonant Frequencies of Multi-pendulums with Numerical Analysis
Speaker: Michal Horanský
Abstract: Resonance can be meaningfully defined for driven systems containing multiple pendulums suspended from one other as maximalisation of mechanical energy in the steady-state trajectory with respect to the driving parameters. For the multipendulum under free conditions, we can calculate the normal modes and their associated frequencies of small oscillations and see they that form a meaningful approximation of the measured resonant response.

In search for a more accurate expression for the resonant frequencies, we hypothesise that the driven steady-state trajectories also behave as modes. We then attempt to perturb the free-condition solutions in mode space to match the corresponding constraint forces to the applied driving forces in order to find the viable solutions. We comment on the span of force vectors which elicit mode behaviour and conclude that, in general, we cannot expect the steady state trajectory to be a mode, even for a small-magnitude driving force.

Talk 2 Title: Characterising he Galactic Centre Excess using Non-Possonian Template Fitting Methods and SkuFACT Diffuse Models
Speaker: Yuqing Wu
Abstract: The Galactic Centre Excess (GCE) has been interpreted as a possible signal from dark matter (DM) annihilating into Standard Model particles. Non-Poissonian Template Fits (NPTFs) may distinguish between DM and the leading alternate hypothesis, an unresolved population of millisecond pulsars (MSPs). This project performs a re-analysis of Fermi gamma-ray datasets using the SkyFACT (Sky Factorization with Adaptive Constrained Templates) diffuse models in place of older diffuse models. We find evidence that SkyFACT provides a significantly better fit, returns physical output parameters, and is more stable to input changes. In addition, the NPTF appears to be sufficiently precise to distinguish various template morphologies for DM and point sources (PSs). The results provide hope that SkyFACT can reveal further insights concerning the GCE.

Date: 8 March 2023 at 12:00 (GMT)
Location: Blackett Lecture Theatre
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Talk 1 Title: Using Multipoint Measurement to Examine Magnetic Reconnection in the Earth's Magnetosheath
Speaker: Clarisse Bonacina
Abstract: Magnetic reconnection is a typical process in astrophysical and space plasmas. Magnetic field lines, frozen in the plasma, get twisted and merge together to change the topology of the field. Understanding magnetic reconnection has practical applications, since the plasma dynamics around the Earth has a direct impact on space weather, but is also a topic of interest from a theoretical perspective, especially in the study of turbulence. Indeed, magnetic reconnection is closely related to plasma turbulence, as it is thought to be one of the driving forces. The aim of my project was to use multipoint measurements from the Magnetospheric Multiscale mission (MMS) to reconstruct the topology of the magnetic field around turbulent reconnection events in the Earth's magnetosheath. 256 reconnection events were reconstructed and classified using the First Order Taylor Expansion (FOTE) method. An attempt at a second-order reconstruction followed, but the physical significance of the results could not be verified.

Talk 2 Title: Path Integrals in Financial Markets: How Quantum Emerges in Finance
Speaker: Emir Sezik
Abstract: Stochastic Models are widely used in mathematical finance, mainly to price derivatives or predict the prices of certain securities. One key application of Stochastic Models is known as the Black-Scholes Option Pricing Formula, which gives a closed form expression for the option prices in terms of few key parameters. In this talk, we will discover how path integrals arise from these Stochastic Models and see how they can be applied to gain key insights from financial markets. We will also talk about how this formalism can be used to simulate different trading strategies and explore their outcome on our portfolio. 

Talk Title: Quantum Embedding — an intuitive approach to strong correlations
Date: 27 October 2021 at 12:00 (BST)
Speaker: Marcell Kovacs
Location: Live online via MS Teams - watch the lecture recording

Abstract: Strongly correlated electronic systems exhibit some of the most remarkable quantum phenomena such as high-temperature superconductivity, metal-insulator transitions as well as antiferromagnetic magnetic order. The Coulomb repulsion between electrons is crucial to the behaviour of these systems which precludes the use of independent particle models as the motion of electrons becomes correlated. These material phases pose a notoriously difficult analytical and computational problem as the many-body effects cannot be treated perturbatively.

Several computational methods, such as stochastic Quantum Monte Carlo simulations, have been developed for this problem in the past decades. For most of these, however, the exponential barrier of simulating large ensembles of particles still prohibits accurate predictions in the thermodynamic limit. In the talk, I will introduce Quantum Embedding Theory, a recent alternative to treat strong correlations in condensed matter models by an effective, compressed representation of the interactions as an open impurity embedded into the environment. The Hubbard model and the dissociation curve of Hydrogen rings will also be discussed to put the performance of embedding into context.

Talk Title: Energy storage and ethical employment within the Solar Cyclone Tower Project
Date: POSTPONED - DATE TO BE CONFIRMED
Speakers: Stefano Fiocca and Shi Yuan
Location: Blackett Lecture Theatre 1

Abstract: The Solar Cyclone Tower is an innovative renewable energy source, consisting of a large chimney connected by a radial system of greenhouses topped with solar panels. As air heats up in the greenhouses, it rises through the chimney where turbines generate electricity. To balance the fluctuating energy output of the tower between day and night and deliver a steady power output, a form of energy storage is required. The main technology used for grid energy storage, pumped hydro-electric, stores the energy in the gravitational potential of water which is pumped to an elevated lake. However, as the SCT requires hot and flat locations, this is not possible. Shi Wei has been comparing innovative energy storage solutions on factors including round-trip efficiency, costs and location. In his research, he found that Liquid Air Energy Storage and Hydrogen Energy Storage both have strong potential for use in combination with the SCT. On top of comparing performance and safety factors, he also looked into potential synergies with the SCT, such as hydrogen export and liquid air for carbon capture.

Solar Cyclone Towers are currently being built in La Paz county, Arizona, USA. While the construction process is being trialled in the States, plans for building dozens of these in the Gulf Cooperation Council countries are being made. More specifically: Oman, the UAE and Qatar. Although Qatar is the most infamous of the three because of the international backlash following incidents related to the 2022 World Cup construction projects, all three countries are rife with human rights abuses. The towers could produce a projected amount of water and fuel to provide food security for all three countries whilst diminishing their reliance on fossil fuels, having worldwide positive implications. However, it will prove much harder to carry out their construction ethically than in La Paz. The final part of this talk explores the legal doctrines and mechanisms that lead to instances of abuse, “forced labor” and “modern slavery” in these countries, exploring the difficulties a western company will experience in trying to avoid these.


Talk Title: Analysis of resonant frequencies of the double-pendulum
Date: 9 February 2022 at 12:00 (GMT)
Speaker: Michal Horansky
Location: Blackett Lecture Theatre 1
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Lecture Slides

Abstract: The mathematical pendulum, which can be modelled as a harmonic oscillator, behaves in a simple way from which resonance emerges trivially. Contrastingly, the double-pendulum is a complex system for which resonance cannot be defined easily and its equations of motion cannot be solved analytically. For some parameter values, however, it exhibits self-damping tendencies for which resonance can be meaningfully defined.

Numerical integration is used to simulate the double-pendulum driven by a harmonic force and the relation of an amplitude-related property to the frequency of the driving force is analyzed for various parameter value sets to obtain an empirical understanding of resonant behaviour therein. The equations of motion are inspected with empirically justified restrictions and hypotheses are proposed to explain the collected data.


Talk Title: Cosmology Through Photometry: Dropout selection in galaxy surveys
Date: 23 March 2022 at 12:00 (GMT)
Speaker: Bilgesu Aydin
Location: Blackett Lecture Theatre 1
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Abstract: An overarching question of cosmology is the mass distribution of the universe. This is crucial in testing gravitational models and can be approached by analyzing the redshift distribution of galaxies. The Lyman break is an inherent element of the spectra from star forming galaxies. The properties of spectral energy distributions and redshift can be used to create redshift bins for galaxies at  3 < z < 5. Without the need for complicated redshift estimators, dropout selection technique could be used in conjunction with magnitude and colour cuts at the photometric bands available. The talk will cover how a realistic galaxy population can be simulated using data-derived luminosity functions and how dropout selection can be used to process data, especially the higher numbers of galaxies that are expected to be imaged with the upcoming LSST survey.

Talk Title: The Satellite, the CCD & the X-ray
Date: 04 November 2020 at 12:00 (GMT)
Speaker: Alex Hodges

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Abstract: Digital cameras are ubiquitous on Earth. Getting them working in space, however, is an ongoing challenge for space scientists. Last summer, I worked on the soft x-ray imager for the European Space Agency's SMILE mission, and I'll be discussing the testing and calibration campaign. We'll cover the design and operation of a charge-coupled device, their behavioural quirks and flaws, and then look at some unexpected behaviour I found - image smearing and ghost x-rays - and why they hadn't been caught. You'll leave knowing what being part of spacecraft development is like, why space instrumentation adds new and exciting challenges to Earth-bound problems - and most importantly - how physics underpins it all.

Talk Title: Moiré Magic in Twisted Bilayer Graphene: from Superlattice to Superconductivity
Date: 09 December 2020 at 12:00 (GMT)
Speaker: Christopher Cheung

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Abstract: 2D materials usually demonstrate novel behaviour and exotic properties. Twisted bilayer graphene (tBLG), one of the simplest 2D materials, has recently been realized in laboratories. The spatial modulation between the two graphene lattices creates the Moiré superlattice. With this extra periodicity, its phase diagram is highly sensitive to doping, temperature, and the electric field. To researchers’ surprise, at the “magic” angle 1.08°, tBLG can change from an insulator to a superconductor depending on the doping. The talk will highlight the experiments that proved tBLG as a highly tunable material for exploring the strongly correlated behaviour in 2D materials. It will also discuss the theoretical work that attempts to understand the band structure and phase diagram of tBLG.

Talk Title: Simulating the Point Spread Function (PSF) of an optical system using Huygens principle
Date: 10 February 2021 at 12:00 (GMT)
Speaker: Lorenzo Versini

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Abstract: In this talk I will discuss how Huygens principle can be used to simulate the Point Spread Function (PSF) of a set of lenses. I will start with introducing Huygens principle to explain diffraction which limits the resolution of an optical system. I will introduce the idea of “wavefront” and how it’s free-space propagation can be computed numerically using the convolution of an appropriate kernel. I will show the advantages of a more general kernel compared to the usual Fresnel kernel. I will then illustrate the process of propagating the wavefront out of a point source through an optical system to find the PSF. Finally I will briefly mention how numerical cleaning algorithms can be used to clean images to regain part of the lost resolution.

Talk Title: Wilson Loops and the Gauge-String Duality
Date: 24 March 2021 at 12:00 (GMT)
Speaker: Omar Shahpo

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Abstract: Essentially every theory that aims to describe particle physics with some success is a gauge theory, a theory where symmetries play a fundamental role.  Within such theories, an important class of observables is what's called Wilson Loops. These observables are important in calculating many effects, such as Bremsstrahlung radiation or understanding QCD confinement.

Yet Wilson loops arise almost under disguise in string theories in curved space. They uncover a deep connection between string theory and supersymmetric gauge theory, leading to powerful evidence for the AdS/CFT conjecture. Most importantly, they allow us to perform hard calculations in gauge theory using easier ones in string theory. How do they do that? Join us to find out!