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Tue 30 Apr 11:15: Radio observations of extra-galactic transients with the AMI-LA telescope

Upcoming talks - 17 hours 15 min ago
Radio observations of extra-galactic transients with the AMI-LA telescope

The Arcminute Microkelvin Imager – Large Array has been instrumental in the study of radio transients. In this talk I will give an overview of the current extragalactic transients monitoring program which is running on AMI -LA. To demonstrate the power of AMI -LA in improving our shock physics in extragalactic transients I will go through two examples of events where AMI -LA has been instrumental. Starting with the most relativistic systems: GRBs have been observed by AMI -LA from as early as 2012 with the ALARRM rapid follow up system. GRB 221009A , also known as the brightest of all time, has demonstrated the unparalleled temporal coverage achievable with AMI -LA from a few hours to over 100 days post burst. AMI -LA has also enabled us to draw conclusions that wouldn’t be possible with other facilities such as the jetted tidal disruption event AT2022cmc that was first reported in 2022. Due to the high cadence light curve with AMI -LA, we were able to prove for the first time, in a model independent manner that the radio emission originated from a highly relativistic outflow. Such a result has been vital in terms of our understand of tidal disruption events and can now infer the presence of off-axis jets such as AT2018hyz.

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Mon 29 Apr 13:00: Cosmology from Non-Gaussian fields

Upcoming talks - Wed, 24/04/2024 - 12:19
Cosmology from Non-Gaussian fields

In this talk I will discuss several challenges towards detecting primordial non-Gaussianties. With the CMB running out of modes, we have started focussing on large scale structure. Measurements of the 21cm brightness temperature allow us to observe almost our entire past light cone. Based on comoving volume arguments, the epoch starting during the dark ages and ending the epoch of reionzation (EoR) potentially contain a lot of modes. Besides being hard to detect, even at these high redshifts, when modes were more linear, I will argue both signal confusion and non-Gaussian covariance have to be considered. During the EoR, the tracer field is very non-Gaussian and standard summary statistics might no longer suffice. I will discuss how machine learning could help solving some of these challenges, while also benefiting efforts to understand astrophysical evolution during these epochs. Finally, ML applications in cosmology are rapidly developing. We should remain cautious and apply common sense. I will discuss an example of what could happen if we don’t.

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Thu 13 Jun 11:30: Title to be confirmed

Upcoming talks - Wed, 24/04/2024 - 10:24
Title to be confirmed

Abstract not available

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Fri 26 Apr 13:00: Uniqueness of extremal black holes in de Sitter

Upcoming talks - Mon, 22/04/2024 - 17:49
Uniqueness of extremal black holes in de Sitter

Uniqueness theorems for black holes with a cosmological constant are only known in a few limited cases. In my talk I present a recent uniqueness theorem for the extremal Schwarzschild-de Sitter black hole within the class of analytic vacuum spacetimes with a positive cosmological constant containing a static extremal Killing horizon. The proof is based on establishing the uniqueness of transverse deformations to the near-horizon geometry at each order in the transverse parameter. I also present a generalisation to charged extremal black holes in de Sitter and discuss the analogous problem in the case of negative cosmological constant. The talk is based on 2309.04238 [gr-qc] and 2403.08467 [gr-qc].

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Mon 13 May 10:00: Which universes does the no-boundary wave function favour?

Upcoming talks - Mon, 22/04/2024 - 09:07
Which universes does the no-boundary wave function favour?

Please notice the unusual schedule (9:45am) and location (MR9) due to previous overlaps with the Dirac lunch and Dirac lecture.

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Tue 30 Apr 13:00: Stellar activity mitigation in radial velocity measurements

None - Fri, 19/04/2024 - 13:58
Stellar activity mitigation in radial velocity measurements

Over the past decades, the radial velocity (RV) community has made tremendous leaps forward in detecting and characterising ever smaller and lighter exoplanets. This trend has been interrupted in recent years, as planetary RV signals below 1 m/s are drowned out by the stars’ activity. The detection of Earth analogues producing an RV effect of about 10 cm/s is therefore currently out of reach. Several avenues are being explored to restore the trend towards the detection of increasingly less massive planets. These include improvements in (1) instruments, (2) observing strategies, (3) RV extraction techniques, (4) stellar activity monitoring, and (5) stellar activity modelling. In this talk, I will focus on points (4), and (5). I will provide an overview of stellar activity mitigation techniques and show how a proxy for stellar magnetic activity induced RV variations can be extracted from intensity spectra in the visible wavelength range, providing an independent estimate of the evolution of the magnetic field.

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Tue 30 Apr 13:00: Stellar activity mitigation in radial velocity measurements

Upcoming talks - Fri, 19/04/2024 - 13:58
Stellar activity mitigation in radial velocity measurements

Over the past decades, the radial velocity (RV) community has made tremendous leaps forward in detecting and characterising ever smaller and lighter exoplanets. This trend has been interrupted in recent years, as planetary RV signals below 1 m/s are drowned out by the stars’ activity. The detection of Earth analogues producing an RV effect of about 10 cm/s is therefore currently out of reach. Several avenues are being explored to restore the trend towards the detection of increasingly less massive planets. These include improvements in (1) instruments, (2) observing strategies, (3) RV extraction techniques, (4) stellar activity monitoring, and (5) stellar activity modelling. In this talk, I will focus on points (4), and (5). I will provide an overview of stellar activity mitigation techniques and show how a proxy for stellar magnetic activity induced RV variations can be extracted from intensity spectra in the visible wavelength range, providing an independent estimate of the evolution of the magnetic field.

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Tue 07 May 11:30: The recently discovered black holes in wide binaries by Gaia astrometry

Upcoming talks - Fri, 19/04/2024 - 13:30
The recently discovered black holes in wide binaries by Gaia astrometry

I will discuss the recent discovery of the three black holes (BH) by Gaia astrometry, concentrating on BH3 , with a mass of 33 M_solar, which is orbited by a very metal poor giant in an orbit of 12 years. The BH in the Gaia BH3 system is more massive than any other Galactic stellar-origin BH known. The Galactic orbit of the system and its metallicity indicate that it probably belongs to the ED-2 stream, which likely originated from a globular cluster that was disrupted by the Milky Way.

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Fri 19 Apr 13:00: Dynamical Gravastars

Upcoming talks - Thu, 18/04/2024 - 14:33
Dynamical Gravastars

I give new results for ``gravastars’’, which are horizonless compact objects that closely mimic mathematical black holes in their exterior geometry, but for which $g_{00}$ is always positive. In my initial formulation, they result from solving the Tolman-Oppenheimer-Volkoff (TOV) equations for relativistic stellar structure, which require continuous pressure, but with an interior density jump from a normal matter equation of state, to an equation of state where pressure plus density approximately sum to zero. We present Mathematica notebooks solving the TOV equations, in which the structure of the gravastar is entirely governed by the Einstein-Hilbert gravitational action (with zero cosmological constant) together with the matter equation of state, with radii where structural changes occur emerging from the dynamics, rather than being specified in advance as in the original Mazur-Mottola gravastars.

My more recent work with a student shows that the interesting ``simulated horizon’’ structure of dynamical gravastars is a property solely of the exterior TOV equations for relativistic matter with appropriate small radius boundary conditions, and will be present for a large class of interior equations of state. The exterior TOV equations can be rewritten in rescaling-invariant form, leading to a two dimensional autonomous system of differential equations which are now being studied numerically and analytically , and for which hopefully some rigorous results can be proved.

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Fri 26 Apr 11:30: The Via Project: Mapping the invisible Galactic halo

Upcoming talks - Wed, 17/04/2024 - 23:35
The Via Project: Mapping the invisible Galactic halo

Abstract not available

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Mon 22 Apr 13:00: The Dark Energy Spectroscopic Instrument (DESI) Year 1 Results: Baryon Acoustic Oscillations and implications for cosmology

Upcoming talks - Wed, 17/04/2024 - 16:55
The Dark Energy Spectroscopic Instrument (DESI) Year 1 Results: Baryon Acoustic Oscillations and implications for cosmology

DESI represents the culmination of multi-years efforts and advanced spectroscopic techniques. Placed at Mayall 4-meter Telescope, DESI harnesses the power of 5,000 robotic fiber positioners, coupled with state-of-the-art spectrographs, to capture the spectral signatures of millions of galaxies and quasars with unprecedented precision. DESI success is also based on the collaborative spirit of its community, more than 400 scientists over 72 institutions. This data release corresponds to the first year of observations; it holds immense scientific promise across a multitude of fronts: from constraining cosmological parameters, mapping the expansion history of the Universe, to the properties of dark energy and the properties of neutrinos. So far only Baryon Acoustic Oscillations (BAO) information has been fully analysed and made public. I will summarise the main findings and the implications for cosmology.

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Fri 26 Apr 11:30: Title to be confirmed

Upcoming talks - Wed, 17/04/2024 - 15:51
Title to be confirmed

Abstract not available

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Fri 10 May 11:30: Title to be confirmed

Upcoming talks - Wed, 17/04/2024 - 08:42
Title to be confirmed

Abstract not available

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Advanced Apprenticeship in Mechanical Engineering

Department of Physics Jobs - Wed, 17/04/2024 - 00:00

The Department of Physics is recruiting an apprentice to their training scheme to start in September 2024. The successful candidate will undertake a structured training programme in Mechanical Engineering. The role is workshop based and the use of equipment used in manufacture both manual and CNC machines plus design as the primary skill using computer aided design (CAD), for which training will be given.

The scheme offers:

  • Full advanced apprenticeship NVQ Level 3 training in conjunction with either West Suffolk College or Cambridge Regional College, including vocational and technical certificate courses

  • A very broad range of experience in a variety of workshops and research groups

  • A supportive working environment and mentoring scheme

  • Involvement with world-leading research activity.

Applicants should have five GCSEs or equivalent at grades A-C, including Mathematics, Science and English, or expect to gain this level of qualification this Summer.

We are looking for an individual who has a real interest in science and technology and how things work, who demonstrates an aptitude for practical problem solving, with good IT and communication skills.

Fixed-term: 4.5 years.

Once an offer of employment has been accepted, the successful candidate will be required to undergo a health assessment.

Click the 'Apply' button below to register an account with our recruitment system (if you have not already) and apply online.

If you have any questions about the application process, please contact the HR team at hr@phy.cam.ac.uk

Please quote reference KA41334 on your application and in any correspondence about this vacancy.

The University actively supports equality, diversity and inclusion and encourages applications from all sections of society.

The University has a responsibility to ensure that all employees are eligible to live and work in the UK.

Mon 13 May 09:45: Which universes does the no-boundary wave function favour?

Upcoming talks - Tue, 16/04/2024 - 15:17
Which universes does the no-boundary wave function favour?

Please notice the unusual schedule (9:45am) and location (MR9) due to previous overlaps with the Dirac lunch and Dirac lecture.

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Mon 13 May 09:45: Which universes does the no-boundary wave function favour?

Upcoming talks - Tue, 16/04/2024 - 13:49
Which universes does the no-boundary wave function favour?

Please notice the unusual schedule due to previous overlaps with the Dirac lunch and Dirac lecture.

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Tue 22 Oct 11:15: Studies of the reionization-era intergalactic and circumgalactic media using cosmological simulations

Upcoming talks - Tue, 16/04/2024 - 00:57
Studies of the reionization-era intergalactic and circumgalactic media using cosmological simulations

TBC

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Tue 11 Jun 11:15: The ionising properties of galaxies at the Epoch of Reionisation with JWST

Upcoming talks - Tue, 16/04/2024 - 00:52
The ionising properties of galaxies at the Epoch of Reionisation with JWST

TBC

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Tue 28 May 11:15: The Black Hole Mass Metallicity Relation and Insights into Galaxy Quenching

Upcoming talks - Tue, 16/04/2024 - 00:49
The Black Hole Mass Metallicity Relation and Insights into Galaxy Quenching

TBC

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Tue 14 May 11:15: Liquid Crystal based adaptive optics

Upcoming talks - Tue, 16/04/2024 - 00:47
Liquid Crystal based adaptive optics

TBC

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