LISA and γ\gamma-ray telescopes as multi-messenger probes of a first-order cosmological phase transition

We study two possible cosmological consequences of a first-order phase transition in the temperature range of $1$ GeV to $10^3$ TeV: the generation of a stochastic gravitational wave background (SGWB) within the sensitivity of the Laser Interferometer Space Antenna (LISA) and, simultaneously, primordial magnetic fields that would evolve through the Universe's history and could be compatible with the lower bound from $\gamma$-ray telescopes on intergalactic magnetic fields (IGMF) at present time. We find that, if even a small fraction of the kinetic energy in sound waves is converted into MHD turbulence, a first order phase transition occurring at temperature between $1$ and $10^6$ GeV can give rise to an observable SGWB signal in LISA and, at the same time, an IGMF compatible with the lower bound from the $\gamma$-ray telescope MAGIC, for all proposed evolutionary paths of the magnetic fields throughout the radiation dominated era. For two values of the fraction of energy density converted into turbulence, $\varepsilon_{\rm turb}=0.1$ and $1$, we provide the range of first-order phase transition parameters (strength $\alpha$, duration $\beta^{-1}$, bubbles wall speed $v_w$, and temperature $T_*$), together with the corresponding range of magnetic field strength $B$ and correlation length $\lambda$, that would lead to the SGWB and IGMF observable with LISA and MAGIC. The resulting magnetic field strength at recombination can also correspond to the one that has been proposed to induce baryon clumping, previously suggested as a possible way to ease the Hubble tension. In the limiting case $\varepsilon_{\rm turb} \ll 1$, the SGWB is only sourced by sound waves, however, an IGMF is still generated. We find that values as small as $\varepsilon_{\rm turb} \sim O(10^{-13})$ (helical) and $O (10^{-9})$ (non-helical) can provide IGMF compatible with MAGIC's lower bound.Comment: 10 pages, 4 figure

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The second data release from the European Pulsar Timing Array: IV. Implications for massive black holes, dark matter, and the early Universe

The European Pulsar Timing Array (EPTA) and Indian Pulsar Timing Array (InPTA) collaborations have measured a low-frequency common signal in the combination of their second and first data releases, respectively, with the correlation properties of a gravitational wave background (GWB). Such a signal may have its origin in a number of physical processes including a cosmic population of inspiralling supermassive black hole binaries (SMBHBs); inflation, phase transitions, cosmic strings, and tensor mode generation by the non-linear evolution of scalar perturbations in the early Universe; and oscillations of the Galactic potential in the presence of ultra-light dark matter (ULDM). At the current stage of emerging evidence, it is impossible to discriminate among the different origins. Therefore, for this paper, we consider each process separately, and investigated the implications of the signal under the hypothesis that it is generated by that specific process. We find that the signal is consistent with a cosmic population of inspiralling SMBHBs, and its relatively high amplitude can be used to place constraints on binary merger timescales and the SMBH-host galaxy scaling relations. If this origin is confirmed, this would be the first direct evidence that SMBHBs merge in nature, adding an important observational piece to the puzzle of structure formation and galaxy evolution. As for early Universe processes, the measurement would place tight constraints on the cosmic string tension and on the level of turbulence developed by first-order phase transitions. Other processes would require non-standard scenarios, such as a blue-tilted inflationary spectrum or an excess in the primordial spectrum of scalar perturbations at large wavenumbers. Finally, a ULDM origin of the detected signal is disfavoured, which leads to direct constraints on the abundance of ULDM in our Galaxy

Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

NANOGrav signal from magnetohydrodynamic turbulence at the QCD phase transition in the early Universe

International audienceThe NANOGrav Collaboration has recently reported evidence for the existence of a stochastic gravitational wave background in the 1–100 nHz frequency range. We argue that such a background could have been produced by magnetohydrodynamic (MHD) turbulence at the QCD scale. From the NANOGrav measurement, one can infer the magnetic field parameters: a comoving field strength close to microGauss and a correlation length close to 10% of the Hubble radius at the QCD phase transition epoch. We point out that the turbulent decay of a nonhelical magnetic field with such parameters leads to a magnetic field at the recombination epoch, which would be sufficiently strong to provide a solution to the Hubble tension problem, as recently proposed. We also show that the MHD turbulence interpretation of the NANOGrav signal can be tested via measurements of the relic magnetic field in the voids of the large scale structure, with gamma-ray telescopes like CTA

LISA and γ\gamma-ray telescopes as multi-messenger probes of a first-order cosmological phase transition

International audienceWe study two possible cosmological consequences of a first-order phase transition in the temperature range of $1$ GeV to $10^3$ TeV: the generation of a stochastic gravitational wave background (SGWB) within the sensitivity of the Laser Interferometer Space Antenna (LISA) and, simultaneously, primordial magnetic fields that would evolve through the Universe's history and could be compatible with the lower bound from $\gamma$-ray telescopes on intergalactic magnetic fields (IGMF) at present time. We find that, if even a small fraction of the kinetic energy in sound waves is converted into MHD turbulence, a first order phase transition occurring at temperature between $1$ and $10^6$ GeV can give rise to an observable SGWB signal in LISA and, at the same time, an IGMF compatible with the lower bound from the $\gamma$-ray telescope MAGIC, for all proposed evolutionary paths of the magnetic fields throughout the radiation dominated era. For two values of the fraction of energy density converted into turbulence, $\varepsilon_{\rm turb}=0.1$ and $1$, we provide the range of first-order phase transition parameters (strength $\alpha$, duration $\beta^{-1}$, bubbles wall speed $v_w$, and temperature $T_*$), together with the corresponding range of magnetic field strength $B$ and correlation length $\lambda$, that would lead to the SGWB and IGMF observable with LISA and MAGIC. The resulting magnetic field strength at recombination can also correspond to the one that has been proposed to induce baryon clumping, previously suggested as a possible way to ease the Hubble tension. In the limiting case $\varepsilon_{\rm turb} \ll 1$, the SGWB is only sourced by sound waves, however, an IGMF is still generated. We find that values as small as $\varepsilon_{\rm turb} \sim O(10^{-13})$ (helical) and $O (10^{-9})$ (non-helical) can provide IGMF compatible with MAGIC's lower bound

LISA and γ\gamma-ray telescopes as multi-messenger probes of a first-order cosmological phase transition

We study two possible cosmological consequences of a first-order phase transition in the temperature range of $1$ GeV to $10^3$ TeV: the generation of a stochastic gravitational wave background (SGWB) within the sensitivity of the Laser Interferometer Space Antenna (LISA) and, simultaneously, primordial magnetic fields that would evolve through the Universe's history and could be compatible with the lower bound from $\gamma$-ray telescopes on intergalactic magnetic fields (IGMF) at present time. We find that, if even a small fraction of the kinetic energy in sound waves is converted into MHD turbulence, a first order phase transition occurring at temperature between $1$ and $10^6$ GeV can give rise to an observable SGWB signal in LISA and, at the same time, an IGMF compatible with the lower bound from the $\gamma$-ray telescope MAGIC, for all proposed evolutionary paths of the magnetic fields throughout the radiation dominated era. For two values of the fraction of energy density converted into turbulence, $\varepsilon_{\rm turb}=0.1$ and $1$, we provide the range of first-order phase transition parameters (strength $\alpha$, duration $\beta^{-1}$, bubbles wall speed $v_w$, and temperature $T_*$), together with the corresponding range of magnetic field strength $B$ and correlation length $\lambda$, that would lead to the SGWB and IGMF observable with LISA and MAGIC. The resulting magnetic field strength at recombination can also correspond to the one that has been proposed to induce baryon clumping, previously suggested as a possible way to ease the Hubble tension. In the limiting case $\varepsilon_{\rm turb} \ll 1$, the SGWB is only sourced by sound waves, however, an IGMF is still generated. We find that values as small as $\varepsilon_{\rm turb} \sim O(10^{-13})$ (helical) and $O (10^{-9})$ (non-helical) can provide IGMF compatible with MAGIC's lower bound

LISA and γ\gamma-ray telescopes as multi-messenger probes of a first-order cosmological phase transition

International audienceWe study two possible cosmological consequences of a first-order phase transition in the temperature range of $1$ GeV to $10^3$ TeV: the generation of a stochastic gravitational wave background (SGWB) within the sensitivity of the Laser Interferometer Space Antenna (LISA) and, simultaneously, primordial magnetic fields that would evolve through the Universe's history and could be compatible with the lower bound from $\gamma$-ray telescopes on intergalactic magnetic fields (IGMF) at present time. We find that, if even a small fraction of the kinetic energy in sound waves is converted into MHD turbulence, a first order phase transition occurring at temperature between $1$ and $10^6$ GeV can give rise to an observable SGWB signal in LISA and, at the same time, an IGMF compatible with the lower bound from the $\gamma$-ray telescope MAGIC, for all proposed evolutionary paths of the magnetic fields throughout the radiation dominated era. For two values of the fraction of energy density converted into turbulence, $\varepsilon_{\rm turb}=0.1$ and $1$, we provide the range of first-order phase transition parameters (strength $\alpha$, duration $\beta^{-1}$, bubbles wall speed $v_w$, and temperature $T_*$), together with the corresponding range of magnetic field strength $B$ and correlation length $\lambda$, that would lead to the SGWB and IGMF observable with LISA and MAGIC. The resulting magnetic field strength at recombination can also correspond to the one that has been proposed to induce baryon clumping, previously suggested as a possible way to ease the Hubble tension. In the limiting case $\varepsilon_{\rm turb} \ll 1$, the SGWB is only sourced by sound waves, however, an IGMF is still generated. We find that values as small as $\varepsilon_{\rm turb} \sim O(10^{-13})$ (helical) and $O (10^{-9})$ (non-helical) can provide IGMF compatible with MAGIC's lower bound

LISA and γ\gamma-ray telescopes as multi-messenger probes of a first-order cosmological phase transition

International audienceWe study two possible cosmological consequences of a first-order phase transition in the temperature range of $1$ GeV to $10^3$ TeV: the generation of a stochastic gravitational wave background (SGWB) within the sensitivity of the Laser Interferometer Space Antenna (LISA) and, simultaneously, primordial magnetic fields that would evolve through the Universe's history and could be compatible with the lower bound from $\gamma$-ray telescopes on intergalactic magnetic fields (IGMF) at present time. We find that, if even a small fraction of the kinetic energy in sound waves is converted into MHD turbulence, a first order phase transition occurring at temperature between $1$ and $10^6$ GeV can give rise to an observable SGWB signal in LISA and, at the same time, an IGMF compatible with the lower bound from the $\gamma$-ray telescope MAGIC, for all proposed evolutionary paths of the magnetic fields throughout the radiation dominated era. For two values of the fraction of energy density converted into turbulence, $\varepsilon_{\rm turb}=0.1$ and $1$, we provide the range of first-order phase transition parameters (strength $\alpha$, duration $\beta^{-1}$, bubbles wall speed $v_w$, and temperature $T_*$), together with the corresponding range of magnetic field strength $B$ and correlation length $\lambda$, that would lead to the SGWB and IGMF observable with LISA and MAGIC. The resulting magnetic field strength at recombination can also correspond to the one that has been proposed to induce baryon clumping, previously suggested as a possible way to ease the Hubble tension. In the limiting case $\varepsilon_{\rm turb} \ll 1$, the SGWB is only sourced by sound waves, however, an IGMF is still generated. We find that values as small as $\varepsilon_{\rm turb} \sim O(10^{-13})$ (helical) and $O (10^{-9})$ (non-helical) can provide IGMF compatible with MAGIC's lower bound