# data[].attributes.body
Suggested by David

# data[].attributes.attachment_link.title
Aspects of Particle Production from Bubble Dynamics at a First Order Phase Transition

# data[].attributes.attachment_link.description
First order phase transitions (FOPTs) constitute an active area of contemporary research as a promising cosmological source of observable gravitational waves. The spacetime dynamics of the background scalar field undergoing the phase transition can also directly produce quanta of particles that couple to the scalar, which has not been studied as extensively in the literature.

# data[].attributes.headline
Reconstructing the early-universe expansion and thermal history

# data[].attributes.subject
Reconstructing the early-universe expansion and thermal history

# data[].attributes.body
(Ben)

# data[].attributes.body
(Ben)

# data[].attributes.attachment_link.description
Effective field theories in flat space and in anti-de Sitter space are constrained by causality and unitarity, often in the form of positivity bounds. Similar bounds have been harder to demonstrate in cosmological backgrounds, where the roles of unitarity and causality are more obscure.

# data[].attributes.headline
Euclid: The search for primordial features

# data[].attributes.subject
Euclid: The search for primordial features

# data[].attributes.body
(Ben)

# data[].attributes.attachment_link.readable_text
Skip to main content

Authors: M. Ballardini, Y. Akrami, F. Finelli, D. Karagiannis, B. Li, Y. Li, Z. Sakr, D. Sapone, A. Achúcarro, M. Baldi, N. Bartolo, G. Cañas-Herrera, S. Casas, R. Murgia, H. A. Winther, M. Viel, A. Andrews, J. Jasche, G. Lavaux, D. K. Hazra, D. Paoletti, J. Valiviita, A. Amara, S. Andreon, N. Auricchio, P. Battaglia, D. Bonino, E. Branchini, M. Brescia, J. Brinchmann, S. Camera, V. Capobianco, C. Carbone, J. Carretero, M. Castellano, S. Cavuoti, A. Cimatti, G. Congedo, L. Conversi, Y. Copin, L. Corcione, F. Courbin, H. M. Courtois, A. Da Silva, H. Degaudenzi, F. Dubath, X. Dupac, M. Farina, S. Farrens, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, B. Gillis, C. Giocoli, A. Grazian, F. Grupp, S. V. H. Haugan, W. Holmes, F. Hormuth, A. Hornstrup, P. Hudelot, K. Jahnke, S. Kermiche, A. Kiessling, M. Kunz, H. Kurki-Suonio, P. B. Lilje, V. Lindholm, I. Lloro, E. Maiorano, O. Mansutti, O. Marggraf, N. Martinet, F. Marulli, R. Massey, E. Medinaceli, S. Mei, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, M. Moresco, L. Moscardini, E. Munari, S. M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, F. Raison, A. Renzi, J. Rhodes et al. (29 additional authors not shown) You must enable JavaScript to view entire author list.

Download a PDF of the paper titled $Euclid$: The search for primordial features, by M. Ballardini and 128 other authors

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Abstract: Primordial features, in particular oscillatory signals, imprinted in the primordial power spectrum of density perturbations represent a clear window of opportunity for detecting new physics at high-energy scales. Future spectroscopic and photometric measurements from the $Euclid$ space mission will provide unique constraints on the primordial power spectrum, thanks to the redshift coverage and high-accuracy measurement of nonlinear scales, thus allowing us to investigate deviations from the standard power-law primordial power spectrum. We consider two models with primordial undamped oscillations superimposed on the matter power spectrum, one linearly spaced in $k$-space the other logarithmically spaced in $k$-space. We forecast uncertainties applying a Fisher matrix method to spectroscopic galaxy clustering, weak lensing, photometric galaxy clustering, cross correlation between photometric probes, spectroscopic galaxy clustering bispectrum, CMB temperature and $E$-mode polarization, temperature-polarization cross correlation, and CMB weak lensing. We also study a nonlinear density reconstruction method to retrieve the oscillatory signals in the primordial power spectrum. We find the following percentage relative errors in the feature amplitude with $Euclid$ primary probes for the linear (logarithmic) feature model: 21% (22%) in the pessimistic settings and 18% (18%) in the optimistic settings at 68.3% confidence level (CL) using GC$_{\rm sp}$+WL+GC$_{\rm ph}$+XC. Combining all the sources of information explored expected from $Euclid$ in combination with future SO-like CMB experiment, we forecast ${\cal A}_{\rm lin} \simeq 0.010 \pm 0.001$ at 68.3% CL and ${\cal A}_{\rm log} \simeq 0.010 \pm 0.001$ for GC$_{\rm sp}$(PS rec + BS)+WL+GC$_{\rm ph}$+XC+SO-like both for the optimistic and pessimistic settings over the frequency range $(1,\,10^{2.1})$.

Submission history

From: Mario Ballardini Dr. [ view email]
[v1] Fri, 29 Sep 2023 14:46:16 UTC (16,511 KB)

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# data[].attributes.attachment_link.title
$Euclid$: The search for primordial features

# data[].attributes.attachment_link.description
Primordial features, in particular oscillatory signals, imprinted in the primordial power spectrum of density perturbations represent a clear window of opportunity for detecting new physics at high-energy scales. Future spectroscopic and photometric measurements from the $Euclid$ space mission will provide unique constraints on the primordial power spectrum, thanks to the redshift coverage and high-accuracy measurement of nonlinear scales, thus allowing us to investigate deviations from the standard power-law primordial power spectrum.

# data[].attributes.headline
Real-time dynamics of false vacuum decay

# data[].attributes.subject
Real-time dynamics of false vacuum decay

# data[].attributes.body
(Aleksandr)

# data[].attributes.attachment_link.title
Real-time dynamics of false vacuum decay

# data[].attributes.attachment_link.description
We investigate false vacuum decay of a relativistic scalar field initialized in the metastable minimum of an asymmetric double-well potential. The transition to the true ground state is a well-defined initial-value problem in real time, which can be formulated in nonequilibrium quantum field theory on a closed time path.

# data[].attributes.body
(suggested by Florian)

# data[].attributes.attachment_link.readable_text
We examine implications of the weak gravity conjecture for the mechanisms for discharging cosmological constant via membrane nucleations. Once screening fluxes and membranes which source them enter, and weak gravity bounds are enforced, a generic de Sitter space \underline{must} be unstable. We show that when all the flux terms which screen and discharge the cosmological constant are dominated by quadratic and higher order terms, the bounds from weak gravity conjecture and naturalness lead toward anthropic outcomes. In contrast, when the flux sectors are dominated by linear flux terms, anthropics may be avoided, and the cosmological constant may naturally decay toward smallest possible values.

Note:

26 pages, 4 .png figures, XeLaTeX; v2: improved presentation, added discussion, fixed typos, added refs

# data[].attributes.attachment_link.title
Implications of Weak Gravity Conjecture for de Sitter Decay by Flux Discharge - INSPIRE

# data[].attributes.attachment_link.description
We examine implications of the weak gravity conjecture for the mechanisms for discharging cosmological constant via membrane nucleations. Once screening flux…

# data[].attributes.body
(Kyrylo)

# data[].attributes.attachment_link.title
Updated Big Bang Nucleosynthesis Bounds on Long-lived Particles from Dark Sectors

# data[].attributes.attachment_link.description
As electromagnetic showers may alter the abundance of Helium, Lithium, and Deuterium, we can place severe constraints on the lifetime and amount of electromagnetic energy injected by long-lived particles. Considering up-to-date measurements of the light element abundances that point to $Y_p=0.245\pm 0.003$,$({\rm D/H})= (2.527\pm 0.03)\times 10^{-5}$,$(^7{\rm Li/H})=1.58 ^{+0.35}_{-0.28} \times 10^{-10}$, $(^6{\rm Li/^7 Li})=0.05$, and the baryon-to-photon ratio obtained from the Cosmic Microwave Background data, $η=6.104 \times 10^{-10}$, we derive upper limits on the fraction of electromagnetic energy produced by long-lived particles. Our findings apply to decaying dark matter models, long-lived gravitinos, and other non-thermal processes that occurred in the early universe between $10^2-10^{10}$ seconds.

# data[].attributes.body
(Evangelos)

# data[].attributes.attachment_link.description
The sine-Gordon model in 3+1 dimensions is known to admit two oscillons of different energy and frequency but comparable lifetime. We show that the oscillon spectrum includes more spherically symmetric ``states″. We identify new high-amplitude oscillons by allowing the field profile to have a number of nodes. For each number of nodes, we find 2 states with a comparable lifetime to the nodeless ones. Oscillons with nodes are, however, unstable to non-spherical perturbations and so their lifetime is significantly reduced. Interestingly, these states are seen to fragment into a collection of nodeless oscillons. The heavy nodeless oscillon is quite remarkable: despite its energy it is stable against fragmentation. Moreover, it has considerably small oscillation frequency, meaning that it can be interpreted as a rather relativistic bound state.

# data[].attributes.body
(David)

# data[].attributes.attachment_link.title
String Theory and the First Half of the Universe

# data[].attributes.attachment_link.description
We perform a detailed study of stringy moduli-driven cosmologies between the end of inflation and the commencement of the Hot Big Bang, including both the background and cosmological perturbations: a period that can cover half the lifetime of the universe on a logarithmic scale.

# data[].attributes.body
(Oksana)

# data[].attributes.attachment_link.title
Gravitational Axiverse Spectroscopy: Seeing the Forest for the Axions

# data[].attributes.attachment_link.description
We consider inflationary models with multiple spectator axions coupled to dark gauge sectors via Chern-Simons (CS) terms. The energy injection into Abelian gauge fields from the axions engenders a multi-peak profile for scalar and tensor spectra.

# data[].attributes.body
(Florian)

# data[].attributes.attachment_link.title
$5 σ$ tension between Planck cosmic microwave background and eBOSS Lyman-alpha forest and constraints on physics beyond $Λ$CDM

# data[].attributes.attachment_link.description
We find that combined Planck cosmic microwave background, baryon acoustic oscillations and supernovae data analyzed under $Λ$CDM are in 4.9$σ$ tension with eBOSS Ly$α$ forest in inference of the linear matter power spectrum at wavenumber $\sim 1 h\,\mathrm{Mpc}^{-1}$ and redshift = 3.

# data[].attributes.body
(Aleksandr)

# data[].attributes.attachment_link.title
Bubble velocities and oscillon precursors in first order phase transitions

# data[].attributes.attachment_link.description
Metastable `false' vacuum states are an important feature of the Standard Model of particle physics and many theories beyond it. Describing the dynamics of a phase transition out of a false vacuum via the nucleation of bubbles is essential for understanding the cosmology of vacuum decay and the full spectrum of observables.

# data[].attributes.body
(Ben)

# data[].attributes.attachment_link.title
Limits on Non-Relativistic Matter During Big-Bang Nucleosynthesis

# data[].attributes.attachment_link.description
Big-bang nucleosynthesis (BBN) probes the cosmic mass-energy density at temperatures $\sim 10$ MeV to $\sim 100$ keV. Here, we consider the effect of a cosmic matter-like species that is non-relativistic and pressureless during BBN. Such a component must decay; doing so during BBN can alter the baryon-to-photon ratio, $η$, and the effective number of neutrino species.

# data[].attributes.body
(David)

# data[].attributes.attachment_link.title
Cosmological Particle Production and Pairwise Hotspots on the CMB

# data[].attributes.attachment_link.description
Heavy particles with masses much bigger than the inflationary Hubble scale $H_*$, can get non-adiabatically pair produced during inflation through their couplings to the inflaton. If such couplings give rise to time-dependent masses for the heavy particles, then following their production, the heavy particles modify the curvature perturbation around their locations in a time-dependent and scale non-invariant manner.

# data[].attributes.body
(Oksana)

# data[].attributes.attachment_link.title
Multi-field curved solid: early dark energy and perturbation instabilities

# data[].attributes.attachment_link.description
We introduce a multi-field dark energy model with a non-flat field-space metric, in which one field is dynamical while the others have constant spatial gradients. The model is predictive at the background level, leading to an early dark energy component at high redshifts and a suppressed fraction of late-time anisotropy.

# data[].attributes.body
(David)

# data[].attributes.attachment_link.title
Comments on the no boundary wavefunction and slow roll inflation

# data[].attributes.attachment_link.description
We review aspects of the Hartle-Hawking no boundary geometry in the context of slow roll inflation. We give an analytic approximation to the geometry and we explain the rationale for the proposal. We also explain why it gives a prediction for the curvature of the universe that is in disagreement with observations and give a quick review of proposed ways to resolve that disagreement.

# data[].attributes.body
(Oksana)

# data[].attributes.attachment_link.title
A novel PBH production mechanism from non-Abelian gauge fields during inflation

# data[].attributes.attachment_link.description
We consider the case of axion-like particles (ALPs) during inflation. When coupled to a non-Abelian gauge sector via a Chern-Simons term, ALPs support an intriguing, testable, phenomenology with very distinctive features including chiral primordial gravitational waves. For sufficiently small values of the gauge vev and coupling, scalar perturbations in the gauge sector exhibit a known instability. We harness the power of such instability for primordial black hole (PBH) generation. In the case of an axion-inflaton, one is dynamically driven into a strong-backreaction regime that crosses the instability band thereby sourcing a peaked scalar spectrum leading to PBH production and the related scalar-induced gravitational waves. Remarkably, this dynamics is largely insensitive to the initial conditions and the shape of the potential, highlighting the universal nature of the sourcing mechanism. In the case of spectator ALPs one can identify the parameter space that sets off the strong backreaction regime and the ensuing features. We show that spectator ALP models may also access the scalar instability region without triggering strong backreaction.

# data[].attributes.body
(Ben)

# data[].attributes.attachment_link.readable_text
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Authors: DESI Collaboration: A. G. Adame, J. Aguilar, S. Ahlen, S. Alam, D. M. Alexander, M. Alvarez, O. Alves, A. Anand, U. Andrade, E. Armengaud, S. Avila, A. Aviles, H. Awan, B. Bahr-Kalus, S. Bailey, C. Baltay, A. Bault, J. Behera, S. BenZvi, A. Bera, F. Beutler, D. Bianchi, C. Blake, R. Blum, S. Brieden, A. Brodzeller, D. Brooks, E. Buckley-Geer, E. Burtin, R. Calderon, R. Canning, A. Carnero Rosell, R. Cereskaite, J. L. Cervantes-Cota, S. Chabanier, E. Chaussidon, J. Chaves-Montero, S. Chen, X. Chen, T. Claybaugh, S. Cole, A. Cuceu, T. M. Davis, K. Dawson, A. de la Macorra, A. de Mattia, N. Deiosso, A. Dey, B. Dey, Z. Ding, P. Doel, J. Edelstein, S. Eftekharzadeh, D. J. Eisenstein, A. Elliott, P. Fagrelius, K. Fanning, S. Ferraro, J. Ereza, N. Findlay, B. Flaugher, A. Font-Ribera, D. Forero-Sánchez, J. E. Forero-Romero, C. S. Frenk, C. Garcia-Quintero, E. Gaztañaga, H. Gil-Marín, S. Gontcho A Gontcho, A. X. Gonzalez-Morales, V. Gonzalez-Perez, C. Gordon, D. Green, D. Gruen, R. Gsponer, G. Gutierrez, J. Guy, B. Hadzhiyska, C. Hahn, M. M. S Hanif, H. K. Herrera-Alcantar, K. Honscheid, C. Howlett, D. Huterer, V. Iršič, M. Ishak, S. Juneau, N. G. Karaçaylı, R. Kehoe, S. Kent, D. Kirkby, A. Kremin, A. Krolewski, Y. Lai, T.-W. Lan, M. Landriau, D. Lang, J. Lasker, J.M. Le Goff et al. (102 additional authors not shown) You must enable JavaScript to view entire author list.

View a PDF of the paper titled DESI 2024 VI: Cosmological Constraints from the Measurements of Baryon Acoustic Oscillations, by DESI Collaboration: A. G. Adame and 200 other authors

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Abstract:We present cosmological results from the measurement of baryon acoustic oscillations (BAO) in galaxy, quasar and Lyman-$\alpha$ forest tracers from the first year of observations from the Dark Energy Spectroscopic Instrument (DESI), to be released in the DESI Data Release 1. DESI BAO provide robust measurements of the transverse comoving distance and Hubble rate, or their combination, relative to the sound horizon, in seven redshift bins from over 6 million extragalactic objects in the redshift range $0.1<z<4.2$. DESI BAO data alone are consistent with the standard flat $\Lambda$CDM cosmological model with a matter density $\Omega_\mathrm{m}=0.295\pm 0.015$. Paired with a BBN prior and the robustly measured acoustic angular scale from the CMB, DESI requires $H_0=(68.52\pm0.62)$ km/s/Mpc. In conjunction with CMB anisotropies from Planck and CMB lensing data from Planck and ACT, we find $\Omega_\mathrm{m}=0.307\pm 0.005$ and $H_0=(67.97\pm0.38)$ km/s/Mpc. Extending the baseline model with a constant dark energy equation of state parameter $w$, DESI BAO alone require $w=-0.99^{+0.15}_{-0.13}$. In models with a time-varying dark energy equation of state parametrized by $w_0$ and $w_a$, combinations of DESI with CMB or with SN~Ia individually prefer $w_0>-1$ and $w_a<0$. This preference is 2.6$\sigma$ for the DESI+CMB combination, and persists or grows when SN~Ia are added in, giving results discrepant with the $\Lambda$CDM model at the $2.5\sigma$, $3.5\sigma$ or $3.9\sigma$ levels for the addition of Pantheon+, Union3, or DES-SN5YR datasets respectively. For the flat $\Lambda$CDM model with the sum of neutrino mass $\sum m_\nu$ free, combining the DESI and CMB data yields an upper limit $\sum m_\nu < 0.072$ $(0.113)$ eV at 95% confidence for a $\sum m_\nu>0$ $(\sum m_\nu>0.059)$ eV prior. These neutrino-mass constraints are substantially relaxed in models beyond $\Lambda$CDM. [Abridged.]

Submission history

From: Dragan Huterer [ view email]
[v1] Wed, 3 Apr 2024 18:41:51 UTC (5,348 KB)

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# data[].attributes.attachment_link.title
DESI 2024 VI: Cosmological Constraints from the Measurements of Baryon Acoustic Oscillations

# data[].attributes.attachment_link.description
We present cosmological results from the measurement of baryon acoustic oscillations (BAO) in galaxy, quasar and Lyman-$α$ forest tracers from the first year of observations from the Dark Energy Spectroscopic Instrument (DESI), to be released in the DESI Data Release 1.

# data[].attributes.body
(Florian)

# data[].attributes.attachment_link.title
Neutron stars and the cosmological constant problem

# data[].attributes.attachment_link.description
Phase transitions can play an important role in the cosmological constant problem, allowing the underlying vacuum energy, and therefore the value of the cosmological constant, to change. Deep within the core of neutron stars, the local pressure may be sufficiently high to trigger the QCD phase transition, thus generating a shift in the value of the cosmological constant. The gravitational effects of such a transition should then be imprinted on the properties of the star. Working in the framework of General Relativity, we provide a new model of the stellar interior, allowing for a QCD and a vacuum energy phase transition. We determine the impact of a vacuum energy jump on mass-radius relations, tidal deformability-radius relations, I-Love-Q relations and on the combined tidal deformability measured in neutron star binaries.

# data[].attributes.body
(Oksana)

# data[].attributes.attachment_link.title
A universal constraint on axion non-Abelian dynamics during inflation

# data[].attributes.attachment_link.description
Inflationary models equipped with Chern-Simons coupling between their axion and gauge sectors exhibit an array of interesting signals including a testable chiral gravitational wave spectrum. The energy injection in the gauge sector triggered by the rolling axion leads to a well-studied enhancement of gauge field fluctuations.

# data[].attributes.attachment_link.title
Percolating Cosmic String Networks from Kination

# data[].attributes.attachment_link.description
We describe a new mechanism, whose ingredients are realised in string compactifications, for the formation of cosmic (super)string networks. Oscillating string loops grow when their tension $μ$ decreases with time. If $2H + \dotμ/μ< 0$, where $H$ is the Hubble parameter, loops grow faster than the scale factor and an initial population of isolated small loops (for example, produced by nucleation) can grow, percolate and form a network. This condition is satisfied for fundamental strings in the background of a kinating volume modulus rolling towards the asymptotic large volume region of moduli space. Such long kination epochs are motivated in string cosmology by both the electroweak hierarchy problem and the need to solve the overshoot problem. The tension of such a network today is set by the final vacuum; for phenomenologically appealing Large Volume Scenario (LVS) vacua, this would lead to a fundamental string network with $G μ\sim 10^{-10}$.

# data[].attributes.body
(Ben)

# data[].attributes.attachment_link.description
The baryon acoustic oscillation (BAO) analysis from the first year of data from the Dark Energy Spectroscopic Instrument (DESI), when combined with data from the cosmic microwave background (CMB), has placed an upper-limit on the sum of neutrino masses, $\sum m_ν< 70$ meV (95%). In addition to excluding the minimum sum associated with the inverted hierarchy, the posterior is peaked at $\sum m_ν= 0$ and is close to excluding even the minumum sum, 58 meV at 2$σ$. In this paper, we explore the implications of this data for cosmology and particle physics. The sum of neutrino mass is determined in cosmology from the suppression of clustering in the late universe. Allowing the clustering to be enhanced, we extended the DESI analysis to $\sum m_ν< 0$ and find $\sum m_ν= - 160 \pm 90$ meV (68%), and that the suppression of power from the minimum sum of neutrino masses is excluded at 99% confidence. We show this preference for negative masses makes it challenging to explain the result by a shift of cosmic parameters, such as the optical depth or matter density. We then show how a result of $\sum m_ν=0$ could arise from new physics in the neutrino sector, including decay, cooling, and/or time-dependent masses. These models are consistent with current observations but imply new physics that is accessible in a wide range of experiments. In addition, we discuss how an apparent signal with $\sum m_ν< 0$ can arise from new long range forces in the dark sector or from a primordial trispectrum that resembles the signal of CMB lensing.

# data[].attributes.attachment_link.title
Null Impact of the Null Energy Condition in Current Cosmology

# data[].attributes.attachment_link.description
We clarify the role of the oft-misunderstood Null Energy Condition (NEC) in the context of the current cosmological data. In particular, the NEC implies the sum of the total energy density and pressure satisfies $ρ_{tot}+P_{tot} \ge 0$; the energy conditions do not apply separately to individual components of the cosmological fluid. Consequently, we show that under the current best-fit cosmological model no violation of the NEC takes place, past or future. Further, growth in the energy density of an individual component cannot be used to signal violation of the NEC. We illustrate these points with a worked example whereby misestimation of the matter density leads to a phase during which $ρ_{de} + P_{de} < 0$ for the effective dark energy, followed by a phantom crossing and subsequent $ρ_{de} + P_{de} > 0$. At no time is the NEC violated. We also introduce ``elephant″ and ``chimera″ classes of physics for crossing $w_{de}=-1$.