Cohomology Chambers on Complex Surfaces and Elliptically Fibered Calabi–Yau Three-Folds

Communications in Mathematical Physics Springer 405:7 (2024) 151

Authors:

Callum R Brodie, Andrei Constantin

Abstract:

We determine several classes of smooth complex projective surfaces on which Zariski decomposition can be combined with vanishing theorems to yield cohomology formulae for all line bundles. The obtained formulae express cohomologies in terms of divisor class intersections, and are adapted to the decomposition of the effective cone into Zariski chambers. In particular, we show this occurs on generalised del Pezzo surfaces, toric surfaces, and K3 surfaces. In the second part we use these surface results to derive formulae for all line bundle cohomology on a simple class of elliptically fibered Calabi–Yau three-folds. Computing such quantities is a crucial step in deriving the massless spectrum in string compactifications.

Electroweak phase transition with a double well done doubly well

Journal of High Energy Physics Springer 2024:6 (2024) 89

Authors:

Prateek Agrawal, Simone Blasi, Alberto Mariotti, Michael Nee

Abstract:

We revisit the electroweak phase transition in the scalar singlet extension of the standard model with a ℤ2 symmetry. In significant parts of the parameter space the phase transition occurs in two steps — including canonical benchmarks used in experimental projections for gravitational waves. Domain walls produced in the first step of the transition seed the final step to the electroweak vacuum, an effect which is typically neglected but leads to an exponentially enhanced tunnelling rate. We improve previous results obtained for the seeded transition, which made use of the thin-wall or high temperature approximations, by using the mountain pass algorithm that was recently proposed as a useful tool for seeded processes. We then determine the predictions of the seeded transition for the latent heat, bubble size and characteristic time scale of the transition. Differences compared to homogeneous transitions are most pronounced when there are relatively few domain walls per hubble patch, potentially leading to an enhanced gravitational wave signal. We also provide a derivation of the percolation criteria for a generic seeded transition, which applies to the domain wall seeds we consider as well as to strings and monopoles.

Laboratory realization of relativistic pair-plasma beams

Nature Communications Nature Research 15:1 (2024) 5029

Authors:

CD Arrowsmith, P Simon, PJ Bilbao, AFA Bott, S Burger, H Chen, FD Cruz, T Davenne, I Efthymiopoulos, DH Froula, A Goillot, JT Gudmundsson, D Haberberger, JWD Halliday, T Hodge, BT Huffman, S Iaquinta, F Miniati, B Reville, S Sarkar, AA Schekochihin, LO Silva, R Simpson, V Stergiou, G Gregori

Abstract:

Relativistic electron-positron plasmas are ubiquitous in extreme astrophysical environments such as black-hole and neutron-star magnetospheres, where accretion-powered jets and pulsar winds are expected to be enriched with electron-positron pairs. Their role in the dynamics of such environments is in many cases believed to be fundamental, but their behavior differs significantly from typical electron-ion plasmas due to the matter-antimatter symmetry of the charged components. So far, our experimental inability to produce large yields of positrons in quasi-neutral beams has restricted the understanding of electron-positron pair plasmas to simple numerical and analytical studies, which are rather limited. We present the first experimental results confirming the generation of high-density, quasi-neutral, relativistic electron-positron pair beams using the 440 GeV/c beam at CERN’s Super Proton Synchrotron (SPS) accelerator. Monte Carlo simulations agree well with the experimental data and show that the characteristic scales necessary for collective plasma behavior, such as the Debye length and the collisionless skin depth, are exceeded by the measured size of the produced pair beams. Our work opens up the possibility of directly probing the microphysics of pair plasmas beyond quasi-linear evolution into regimes that are challenging to simulate or measure via astronomical observations.

A new standard for the logarithmic accuracy of parton showers

ArXiv 2406.02661 (2024)

Authors:

Melissa van Beekveld, Mrinal Dasgupta, Basem Kamal El-Menoufi, Silvia Ferrario Ravasio, Keith Hamilton, Jack Helliwell, Alexander Karlberg, Pier Francesco Monni, Gavin P Salam, Ludovic Scyboz, Alba Soto-Ontoso, Gregory Soyez

More Axion Stars from Strings

(2024)

Authors:

Marco Gorghetto, Edward Hardy, Giovanni Villadoro