DEPARTMENT OF PHYSICS / HIP JOINT COLLOQUIA / SEMINARS 2024

  • Thursday 25 January 2024 at 10:15 in A315 and using Zoom: Saga Säppi (Munich)
    Mass effects and bulk viscosity in high-density QCD
    Abstract: With gravitational wave observations probing neutron stars through their mergers in new ways, there is an increasingly pressing need for improved theoretical predictions. In this context, there are properties of extremely dense matter to which traditional measurements of quiescent neutron stars are insensitive to. One example of this is the effect of quark masses: In the study of the equation of state of neutron stars, masses can often be neglected.  However, these mass effects can become unexpectedly important in the context of mergers. Looking at the problem through the point of view of perturbative high-density QCD, existing methods of taking masses into account often involve convoluted formulas and relatively delicate numerical integrals—this is particularly true at finite temperatures, also a necessary ingredient for realistic mergers simulations. I will explain a simpler approximate method of dealing with these finite-mass loop integrals in perturbative thermal field theory, vastly simplifying existing calculations while maintaining good accuracy. This method can be applied to the computation of bulk viscosity, a transport quantity which is particularly important for merger scenarios, and something which vanishes when mass effects are neglected. By doing so, we have obtained a state-of-the-art evaluation of the bulk viscosity of unpaired quark matter at extremely high densities, with the QCD bulk quantities contributing to it now well under control. The pQCD results can be compared with holography, applicable down to much lower densities, resulting in a beautifully compact approximate pocket formula usable in neutron star simulations.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=184a03a8-7fbb-4202-8afc-807323164f32
  • Tuesday 30 January 2024 at 10:15 in A315 and using Zoom: Elina Palmgren (Helsinki)
    Teaching (theoretical) physics for student deep learning: perspectives from physics education research
    Abstract:
    In studies of higher education, it has been shown that approaches to teaching are affected by discipline: instructors of natural sciences tend to have content-based approaches to teaching, while instructors of humanistic sciences are on average more inclined towards learning-focused approaches (cf. Lindblom‐Ylänne et al., 2006). The content-focused approaches emphasize conveying the taught content to students and are linked to surface learning, whereas the learning-focused approaches aim at fostering students’ active knowledge building and are linked to deep learning. It has been speculated that the variations in the teaching approaches depend on the academic traditions and historical teaching methods of disciplines. Moreover, the characteristics of the discipline affect the teaching approach, as the knowledge structure of the discipline guides the choice of the approach. More specifically in the case of physics, the knowledge structure is cumulative, hierarchical, and mathematically structured, which may lead to sequential and factual content-based teaching that often forgets to emphasize the holistic structures and interconnections between topics.In this talk, some ideas for more learning-focused approach to teaching (theoretical) physics are presented. Especially the role of mathematics as a holistic structure of physical theories, that could be utilized in teaching, is considered. The topic is discussed from the physics education perspective, reflecting on how to turn the mathematical nature of physics into an asset for deep learning.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=a8137130-8967-4510-8138-6239eb1c4b81
  • Tuesday 20 February 2024 at 10:15 in A315 and using Zoom: Benoit Laurent (McGill)
    First principles determination of bubble wall velocity and local thermal equilibrium approximation.
    Abstract:
    First-order phase transitions in the early Universe are well-motivated events predicted by several BSM models. In the first part of this talk, I will derive the fluid equations needed to compute the bubble wall velocity from first principles. By treating the background and out-of-equilibrium perturbations in a consistent way, the resulting equations are free of the discontinuity at v_w=c_s that was observed in previous studies. I will show that the solutions can naturally be classified as deflagration/hybrid walls (v_w ~ c_s) or ultrarelativistic detonations. In the second part, I will explain how this calculation can be significantly simplified when local thermal equilibrium (LTE) is maintained in the plasma. Using this LTE assumption, the fluid equations can be reexpressed in terms of only four parameters that completely characterize a particle physics model. I will present an efficient algorithm to solve these equations and discuss the properties of their solutions. Finally, I will compute the kinetic energy fraction which is essential for predicting the gravitational wave spectrum produced during the phase transition
  • Thursday 22 February 2024 at 10:15 in A315 and using Zoom: Helena Kolesova (Stavanger)
    Non-Abelian dark sectors: gravitational waves vs dark matter
    Abstract:
    Taking axion inflation as an example, we study the evolution of a non-Abelian dark sector coupled to the inflaton for different choices of the confinement scaleFor confinement scales just a few orders of magnitude below the Planck scale, gravitational wave signal could be generated due to fluctuations in the thermal plasma. Another possible source of gravitational waves is the confinement phase transition; however, this signal might be strongly suppressed due to the presence of an early matter-dominated era. We also study the reheating of Standard Model fields and glueball dark matter within this scenario, which, on the other hand, seems to be possible at lower confinement scales.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=4b6fbdf1-1a09-4b2b-b17b-77fe6cbbd9b9
  • Thursday 29 February 2024 at 15:15 in D106 (note location and time!) and using Zoom: Sarah Williams (Cambridge)
    The Future Circular Collider as a Higgs/top/EW Factory: status and plans for FCC-ee
    Abstract: The 2020 update to the European Strategy for Particle Physics laid out several key priorities for the future of collider physics beyond the Large Hadron Collider (LHC). It identified an electron-positron Higgs factory as the next high-priority experiment and encouraged CERN and its international partners to investigate the technical and financial feasibility of a 100 TeV hadron collider. The integrated Future Circular Collider (FCC) project aims to combine these goals, and would involve a ~90km tunnel being used first for e+e- collisions (FCC-ee) and then for 100 TeV proton-proton collisions (FCC-hh) with additional opportunities for electron proton (FCC-eh) and heavy ion collisions. This seminar will discuss the physics opportunities of FCC-ee, and the status of the FCC feasibility study which is ongoing and has just undergone its mid-term review ahead of completion in 2025. I will also discuss the roadmap ahead which could enable FCC-ee to begin operation in the late 2040s.
  • Friday 8 March 2024 at 10:15 in A315 and using Zoom: Michael Doser (CERN)
    Quantum Sensing for (low and high energy) particle physics
    Abstract:
    The seminar will provide a glimpse of some elements of the rapidly evolving field of quantum sensing, specifically focusing on particle physics. Specific approaches involving quantum systems, such as low-dimensional systems or manipulations of ensembles of quantum systems, hold great promise for improving high-energy particle physics detectors, particularly in areas like calorimetry, tracking, and timing. The use of quantum sensors for high-precision measurements, as well as the development of new quantum sensors based on superconducting circuits, ion and particle traps, crystals, and nanomaterials, are equally relevant for low energy particle physics and for fundamental physics.However, significant advances and improvements in existing or future quantum technologies will be necessary to address such topics related to the dark universe, the detection of relic neutrinos, precision tests of symmetries and of the standard model and probing general foundational issues in physics. The seminar will thus also feature discussions of the Quantum Sensing Initiatives at CERN and the ECFA R&D Roadmap on Quantum Sensing and Advanced Technologies and will discuss options for future collaborations in the context of the imminent implementation of this roadmap.
  • Tuesday 12 March 2024 at 10:15 in A315 and using Zoom: Juska Pekkanen (CERN)
    FCC project and ALLEGRO detector concept
    Abstract:
    The Future Circular Collider (FCC) is CERN’s next flagship project which fulfills the physics goals of the 2020 update of the European strategy for particle physics set by the European Committee for Future Accelerators. The proposed accelerator would be placed in a 91 km long tunnel to be bored down to 560 m deep under the Geneva region, with the first phase being an electron-positron collider (FCC-ee), followed by an update to a hadron machine (FCC-hh) with proton-proton collision energies of up to 100 TeV. ALLEGRO is a proposed general-purpose experiment for FCC-ee, with a high-granularity noble-liquid electromagnetic calorimeter as a central feature. In this seminar I will give an overview to the status of the FCC project and introduce the ALLEGRO detector concept, with focus on the progress in the development of the next-generation noble-liquid calorimetry technology.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=d4617bca-0dc6-41fe-8ce4-41873076acec
  • Tuesday 19 March 2024 at 10:15 in A315 and using Zoom: Michal Heller (Ghent)
    Beyond (real) geodesics and extremal hypersurfaces in gravity
    Abstract: 
    Geodesics and extremal hypersurfaces play a critical role in the contemporary understanding of gravity. They compute certain correlation functions, various notions of entropy and, at least sometimes, complexity. I will discuss a new look at this venerable idea motivated by a lack of real extremal surfaces due to de Sitter expansion in cosmologies or timelike separation of boundary points (subregions) in anti-de Sitter holography. Based on 2305.11280 and work in progress with Fabio Ori and Alex Serantes.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=92ceb299-98b5-449c-8da5-fb0cf8792a63
  • Thursday 4 April 2024 at 12:15 in A315 and using Zoom: Karapet Mkrtchyan (London)
    Democratic approach to p-forms and electric-magnetic duality
    Abstract:
    I will summarize recent progress on the democratic covariant Lagrangian formulation of (chiral) p-form dynamics, including arbitrary abelian interactions. Applications include democratic formulations for the gauge sector of maximal supergravities in 10d/11d, with on-shell values of their actions consistent with AdS/CFT predictions.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=17ffea06-cea6-414d-b5a7-21f5c84f2ca2
  • Tuesday 9 April 2024 at 10:15 in A315 and using Zoom: David Benisty (FIAS, Frankfurt and KICC, Cambridge)
    Constraining Dark Energy from the Local Group dynamics
    Abstract:
    In this talk I’ll show a method to constrain the Cosmological Constant \Lambda from binary galaxies, focusing on the Milky Way and Andromeda galaxies. We provide an analytical solution to the two-body problem with \Lambda and show that the ratio between the Keplerian period and T_\Lambda = 2\pi/(c \sqrt{\Lambda}) \approx 63.2 Gyr controls the importance of effects from the Cosmological Constant. The Andromeda-Milky Way orbit has a period of \sim 20 Gyrs and so Dark Energy has to be taken into account.  Using the current best mass estimates of the Milky Way and Andromeda galaxies, we find the Cosmological Constant value based only on the Local Group dynamics to be lower than 5.44 times the value obtained by Planck. With future astrometric measurements, the bound on the Cosmological Constant can be reduced to \left(1.67 \pm 0.79\right) \Lambda_{\rm PL}. Our results offer the prospects of constraints on \Lambda over very different scales than previously. The Local Group provides also a completely novel platform to test alternative theories of gravity. We illustrate this by deriving bounds on scalar-tensor theories of gravity over Megaparsec scales.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=0f27d7f5-3cd2-4a45-bb32-8b2b0db9f9a2
  • Thursday 11 April 2024 at 10:15 in A315 and using Zoom: Christian Ecker (Frankfurt)
    Exploring the Phase Diagram of QCD with Neutron Star Mergers in the Prompt and Non-Prompt Collapse Regime
    Abstract:
    Determining the phase structure of Quantum Chromodynamics (QCD) and its Equation of State (EoS) at densities and temperatures realised inside neutron stars and their mergers is a long-standing open problem. I will present a framework for the EoS of dense and hot QCD that describes the deconfinement phase transition between a dense baryonic and quark matter phase via the holographic V-QCD model. This model is then used to study the consequences on the formation of quark matter in binary neutron star mergers in the prompt and non-prompt collapse regime.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=621819fb-c411-49d5-ab9f-6c1eb7bdc932
  • Tuesday 14 May 2024 at 10:15 in A315 and using Zoom: Tyler Gorda (Frankfurt)
    Probing the behavior of strongly interacting matter at the highest densities
    Abstract:
    The cores of the most massive neutron stars contain the densest matter in the universe. What is possible to learn about the behavior of matter near these densities? In this talk, I will discuss two recent papers that study this question. In the first half, I focus on the interplay between information from perturbative QCD calculations and astrophysical data and how these jointly constrain the behavior of matter in the vicinity of the maximum neutron-star density. In the second half, I turn to the post-merger phase of a binary neutron-star merger and highlight a new way to pinpoint the maximum pressure and densities probed in nature.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=c7b058cf-b5a4-4480-9c7e-9602ab48371e
  • Tuesday 21 May 2024 at 10:15 in A315 and using Zoom: David Milstead (Stockholm)
    Search for baryon number violation and other phenomena with the HIBEAM experiment at the European Spallation Source
    Abstract: The violation of baryon number is an essential ingredient for the preferential creation of matter over antimatter needed to account for the observed baryon asymmetry in the Universe. However, such a process has yet to be experimentally observed. The HIBEAM/NNBAR program is a proposed two-stage experiment at the European Spallation Source to search for baryon number violation. The program will include high-sensitivity searches for processes that violate baryon number by one or two units: free neutron–antineutron oscillation via mixing, neutron–antineutron oscillation via regeneration from a sterile neutron state and neutron disappearance; the effective process of neutron regeneration is also possible. The program can be used to discover and characterize mixing in the neutron, antineutron and sterile neutron sectors. Furthermore, the intense neutron beam can be used to search for phenomena beyond neutron mixing, such as axions. The experiment addresses topical open questions such as the origin of baryogenesis and the nature of dark matter, and is sensitive to scales of new physics substantially in excess of those available at colliders. A key goal of the program is to open a discovery window to neutron conversion probabilities (sensitivities) by up to three orders of magnitude compared with previous searches. The opportunity to make such a leap in sensitivity tests should not be squandered. The experiment pulls together a diverse international team of physicists from the particle (collider and low energy) and nuclear physics communities, while also including specialists in neutronics and magnetics. A conceptual design report, funded by European Union, for the NNBAR stage has been published. A similar paper for the HIBEAM stage will be complete in 2024.
  • Thursday 23 May 2024 at 14:15 in E204: Hannu Kurki-Suonio (Helsinki)
    Farewell lecture; Hannu retires on 1 July 2024
  • Tuesday 28 May 2024 at 10:15 in A315 and using Zoom: Priyotosh Bandyopadhya (IIT Hyderabad)
    Displaced heavy leptons at colliders
    Abstract:
    The most exciting new physics that we are hoping to see are heavy neutrinos and dark matter which can address a few unsolved issues in the Standard Model. However, the regular searches for these new physics scenarios did not give us any hint of the observation. Certainly, we now look for more exootic new physics scenarios, one of which is the displaced vertex scenarios. In this talk we address Type-I, Type-III seesaw and Vector like leptons which can be probed via the displaced heavy neutrinos, displaced Higgs production, displaced double recoil, and displaced deccays doubly charged leptons. These prospects are discussed for the CMS, ATLAS and the proposed MATHUSLA detectors at the LHC, and for the proposed multi-TeV muon collider.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=98f8d2e1-766a-4131-b371-6e77a285f68a
  • Thursday 30 May 2024 at 10:15 in A315 and using Zoom: Carlos Hoyos (Oviedo)
    Spinodal slowing down and scaling in a holographic model
    Abstract: We construct a holographic model of a strongly coupled system with two equilibrium homogeneous phases separated by a first order phase transition at nonzero temperature. We consider a temperature evolving in time and driving the system through the transition point. In the holographic model bubble nucleation is suppressed, so that the system can in principle remain close to a equilibrium phase up to the spinodal temperature where the phase disappears. We study the behaviour close to the spinodal point and show that it shares qualitative features with critical points of second order phase transitions, namely critical slowing down of perturbations. Similarly to critical points, this leads to the breakdown of quasistatic evolution close to the spinodal point with a characteristic scaling depending on the critical exponents.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=88ea6572-34c9-47ac-af26-526cd6975f1e
  • Tuesday 4 June 2024 at 10:15 in A315 and using Zoom: Kirtiman Ghosh (IOP Bhubaneswar)
    A minimal model to explain non-zero neutrino masses/mixings, muon anomalous magnetic moment, and dark matter relic density
    Abstract: The Standard Model (SM) of particle physics is a highly successful framework, as all its predictions have been experimentally verified. However, there are several experimental results, such as neutrino oscillation data, anomalous magnetic moments of charged leptons, and the dark matter relic density, etc., that cannot be explained within the SM framework. These discrepancies motivate the search for new physics models at the TeV scale. In this talk, I will discuss a few simple extensions of the SM that can address some of its inadequacies. I will mainly focus on our recently proposed minimal framework for a radiative seesaw model, which can simultaneously explain neutrino oscillation data, and anomalies in muon g-2, and provide a cosmologically viable candidate for dark matter.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=fa7299a5-d1a2-4ea9-9930-6de402ad9102
  • Thursday 6 June 2024 at 10:15 in A315 and using Zoom: Lusaka Bhattacharya (Bhubaneswar)
    Probing QGP Properties at LHC-HIC Using Photons and Heavy SM Particles
    Abstract:
    The quark-gluon plasma (QGP), a state of deconfined quarks and gluons, emerges as a many-body aspect of quantum chromodynamics (QCD). Heavy-ion collision (HIC) experiments at the LHC and RHIC explore the QCD phase diagram at ultra-high temperatures where QGP is expected. While indirect QGP signatures like jet quenching have been observed, many of its properties remain unclear. This talk discusses using photons to probe QGP characteristics such as isotropization and thermalization. With increased center-of-mass energy in Pb-Pb collisions at the LHC, a new regime of heavy-ion physics allows the study of massive Standard Model (SM) particles like W/Z bosons, the Higgs boson, top quarks, and hard jets. The presentation covers ongoing work on searching for these SM resonances at the LHC-HIC.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=70716f50-a80a-4eba-b2d7-dc4936ccfcb9
  • Thursday 13 June 2024 at 10:15 in A315 and using Zoom: Yuki Fujimoto (Seattle)
    Dense QCD equation of state: Lessons from neutron stars, lattice, and large-Nc QCD
    Abstract:
    I will discuss the QCD equation of state (EoS) at high baryon density. The talk is mainly divided into two parts.In the first part, I explain two consequences from the recent lattice QCD calculations at finite isospin chemical potential, known to be free of the sign problem. I first explain the uses of rigorous QCD inequalities and input from the lattice QCD that put robust bounds on the symmetric nuclear matter EoS at finite baryon density. Then, I compare the weak-coupling results with the lattice data. In particular, I address the following issues: applicability of the weak-coupling results and color superconductivity.In the second part, I explain a duality between dense baryon and quark matter implied from the large-Nc limit of QCD; it is known as Quarkyonic duality. We construct an explicit dual description of Quarkyonic matter using an exactly solvable ideal gas model and demonstrate that the duality can be responsible for the rapid stiffening in the EoS.
  • Tuesday 13 August 2024 at 10:15 in A315 and using Zoom: Shinsuke Kawai (Sungkyunkwan University, Korea)
    The minimal model of cosmology
    Abstract:
    Renormalisation group analysis with the present measurements of the top quark mass m_t = 172.69\pm 0.30 GeV indicates that the Standard Model (SM) Higgs potential becomes unstable at energy scales \sim 10^{10} GeV. This may be interpreted as hinting at new particles at high energy. The minimal extension of the SM that can avoid this instability while leaving the SM Higgs as the sole scalar particle of the theory is obtained by adding suitable fermions to the SM. These fermions are good dark matter candidates and the model is known as the minimal dark matter model.
    We revisit the inflationary scenario based on the minimal dark matter model, taking into account updated parameter constraints and recent understanding of reheating dynamics. We explore the model with different values of the right-handed neutrino mass and find that the cosmological prediction is insensitive to such details. We obtained a spectral index of the cosmic microwave background n_s=0.9672 and a tensor-to-scalar ratio r=0.0031 as a robust prediction of this scenario. [based on arXiv: 2307.08375]
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=495dd2c3-a32f-4b7d-91a4-4a2db3db9094
  • Monday 9 September 2024 at 10:15 in A315 and using Zoom: Arttu Rajantie (Imperial College, London)    Note day!
    Magnetic monopoles from heavy ion collisions
    Abstract: There are good theoretical reasons to believe that magnetic monopoles – particles with a single magnetic north or south pole – should exist, but no sign of them has been seen in astrophysical observations and cosmic ray searches. This indicates that they do not seem to be present in large numbers in the Universe today. But could they be produced in particle collisions at the LHC or future colliders? In this talk, I will review the experimental and theoretical status of these searches. Theoretical problems make it impossible to draw firm conclusions from proton-proton collisions, but the dual Schwinger pair production process in ultraperipheral heavy ion collisions provides a reliable alternative approach, which the MoEDAL and ATLAS collaborations have recently used with heavy ion collisions at the LHC to place lower bounds on the mass of magnetic monopoles. I will discuss these searches and prospects for future colliders.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=b4d76a71-6022-4312-8477-da4a1938110f
  • Tuesday 17 September 2024 at 12.00-13.00 in A315: Sami Lehti (for the Helsinki CMS group) will chair a session of watching a seminar from CERN:
    High-precision measurement of the W boson mass at CMS
  • Tuesday 8 October 2024 at 10:15  using Zoom: Andrei Golutvin (Imperial College & CERN)
    The SHiP experiment at CERN
    Abstract: The SHiP experiment is a general-purpose intensity-frontier experiment for the search of feebly interacting GeV-scale particles and to perform neutrino physics measurements at the HI-ECN3 (high-intensity) beam facility at the CERN SPS, operated in beam-dump mode, taking full advantage of the available 4×10^19 protons per year at 400 GeV. CERN recently approved SHiP for the future programme of this facility. The setup consists of two complementary detector systems. The former, the scattering and neutrino detector (SND), consists of a light dark matter (LDM) / neutrino active target. The latter, the hidden sector decay spectrometer (HSDS), consists of a 50 m long decay volume followed by a spectrometer, timing detector, and a PID system. SHiP offers an unprecedented sensitivity to decay and scattering signatures of various new physics models and tau neutrino physics.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=4df9a1f1-09b7-4d27-8593-218ae34301b7
  • Tuesday 22 October 2024 at 10:15 in A315 and using Zoom: Ananya Tapadar (IACS, Kolkata)
    Non-thermal production of Dark Matter in an EFT scenario
    Abstract: Here we aim to unveil a scenario with a non-minimal secluded dark sector in an effective field theory (EFT) framework. To explore this, we have examined a suitable extension of the type-X Two Higgs Doublet Model (2HDM) as a potential origin for the secluded DS. The DS comprises a DM candidate and a portal particle ‘a’. It becomes non-thermally populated through diverse dim-6 four-Fermi operators, effectively generated by integrating out the heavier Higgs particles which serve as the mediators between the two sectors. The analysis further focuses on the consequences of the collision processes DM + a ↔ a + a and DM + DM ↔ a + a occurring within the DS. We have investigated the significance of employing an EFT approach in tracking the temperature evolution of the DS. Within the present framework, the observed relic abundance of the DM can be realized through both dark freeze-out and freeze-in mechanisms. Further, we have delineated the permissible ranges of the relevant parameters, viz., the DM mass (mχ ≳ 20 GeV), the portal coupling (Cτ ≲ 10−14 GeV−2), and the DS coupling (λ ≲ 10−6 GeV−2) by taking into account the perturbativity of the involved couplings while reproducing the observed DM relic and complying with the bounds from a successful Big Bang Nucleosynthesis (BBN) and γ-ray searches.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=e134306e-a851-4a87-aa05-95488e135f0e
  • Tuesday 19 November 2024 at 10:15 in A315 and using Zoom: Kuang Zhang (Helsinki)
    Lattice and Finite-Element Simulations of Quench Dynamics and Defects of p-wave GL Effective Theory of Superfluid ^3He
    Abstract: Ginzburg-Landau (GL) effective theory is a widely accepted theoretical frame of physical systems with phase transitions. For the case of superfluid liquid $^3$He, a p-wave GL theory is used. Because the p-wave nature of the Cooper pair of condensation, superfluid order parameter of liquid $^3$He is a tensor with 18-real components, and the equation of motion is a coupled non-linear system of 18 PDEs. This complexity obstructs researchers’ understanding of certain physics in a p-wave superlfuid, such as phase transition dynamics, topological defects and boundary effects etc. In this talk, I will present how we utilize the sophisticated HPC tools, which are developed by communities of lattice field theory and computational mathematics on hybrid CPU-GPU platforms, to overcome this difficulty. In particular, I will discuss lattice simulations of a first order transition between superfluid A- and B- phase under temperature quench, the applications of adaptive finite element method on resolving cosmology-like topological defects and spatial modulated configurations of order parameters in superfluid under nano-confinement.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=a8c4292e-7559-4db5-a9e5-12677fc90bc2
  • Friday 29 November 2024 at 10:15 in A315: Dieter Haidt (Desy)
    From Fermi to neutral currents and their impact
    Abstract:
    The discovery of weak neutral currents in the Gargamelle experiment at CERN (1973) will be described and discussed in its historic context. Initially, the community was rather skeptical about the Gargamelle analysis, since at the same time a prominent American group had also presented an analysis denying the existence of weak neutral current. The discovery was the very first experimental verification, which gave substance to the theory of Weinberg published a few years before. In retrospect, the discovery was the beginning of electroweak physics and had an enormous impact in establishing the Standard Model of today.
  • Tuesday 10 December 2024 at 10:15 in A315 and using Zoom: Niccolò Forzano (Swansea)
    Thermal evolution of dark matter symplectic glueballs
    Abstract: We investigate a novel model for dark matter within a dark Yang–Mills theory governed by a symplectic gauge group, which presents similarities and differences from SU(N) models. We first determine the equation of state for this theory, focusing on temperatures near the phase transition and calculating the associated latent heat. We then explore the evolution of this dark matter model in the early universe, examining mechanisms for its potential indirect interactions with the visible sector, the gravitational wave spectrum it could generate, and the resulting relic abundances.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=4f95bb7c-e4e0-43d9-bbcf-91af5a2b345f
  • Tuesday 17 December 2024 at 10:15 in A315 and using Zoom: Timo Lähde (Jülich)
    Emergent alpha clustering in the carbon nucleus from Nuclear Lattice EFT
    Abstract: The formation of alpha clusters in light and medium-mass nuclei plays an important role in determining their spectra and properties. This includes the enigmatic Hoyle state of carbon-12, which is particularly important both astrophysically and anthropically. In the ab initio framework of Nuclear Lattice Effective Field Theory (NLEFT), such clustering effects emerge spontaneously. I will discuss recent work by the NLEFT collaboration on the rich and varied alpha-cluster structures that emerge among the low lying states in the carbon-12 nucleus, even for a highly simplified Wigner SU(4) symmetric nucleon-nucleon interaction.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=cba946ed-6be4-4b59-97df-5a1c9eaa5a9c
  • Thursday 19 December 2024 at 10:15 in A315 and using Zoom: Sebastian Sassi (Helsinki)
    Challenges in modeling direct detection of dark matter
    Abstract: Majority of direct detection analyses historically assume the Standard Halo Model velocity distribution, and isotropic targets. Under these assumptions the dark matter event rate integrals have a closed form solution. However, these assumptions do not hold in general. Some detector materials have isotropic responses, and there is growing interest in studying alternative velocity distributions. Few studies have investigated the computation of event rate integrals in the general case, and naive numerical integration is typically used. I discuss some of the motivation in challenges in considering anisotropic responses and non-SHM velocity distributions, and introduce a novel method for solving the event rate integrals, which takes advantage of a fast Radon transform method using a basis function expansion of the velocity distribution.
    Link to video: https://unitube.it.helsinki.fi/unitube/embed.html?id=4adb985a-0184-4c6b-82d0-be46cab880d4