We investigate entanglement islands and the Page curve in the framework of Horndeski gravity on a Karch-Randall braneworld background. In particular, treating the holographic boundary conformal field theory analytically we find that the Horndeski parameters significantly alter the behavior of the Page curve compared to standard general relativity, a feature caused by the nontrivial geometry induced by the Horndeski scalar field. Interestingly enough, the geometry far from the AdS limit plays a more significant role compared to previous studies. This suggests that Horndeski gravity introduces important modifications to the distribution of quantum information in the holographic model. Finally, we claim that holographic consistency can be used reversely to impose constraints on Horndeski gravity itself, providing a new tool for probing the validity of modified gravity theories.

Brazil

Fabiano Santos

Iran

Azerbaijan

Behnam Pourhassan

Chile

China

Greece

Emmanuel Saridakis

Ukraine

Oleksii Sokoliuk

Alexander Baransky

Türkiye

Emre Kahya

Holographic boundary conformal field theory within Horndeski gravity

On 22nd September 2017, the IceCube Collaboration detected a neutrino with energy of about 290 TeV from the direction of the gamma-ray blazar TXS 0506+056, located at a distance of about 1.75 Gpc. During the same time, enhanced gamma-ray flaring was also simultaneously observed from multiple telescopes, giving rise to only the second coincident astrophysical neutrino/photon observation after SN 1987A. We point out that for this event, both neutrinos and photons encountered a Shapiro delay of about 6300 days along the way from the source. From this delay and the relative time difference between the neutrino and photon arrival times, one can constrain violations of Einstein’s Weak Equivalence Principle (WEP) for TeV neutrinos. We constrain such violations of WEP using the Parameterized Post-Newtonian (PPN) parameter $$\gamma $$ <math><mi>γ</mi></math> , which is given by $$|\gamma _\mathrm{{\nu }}-\gamma _{\mathrm{EM}}|&lt;5.5 \times 10^{-2}$$ <math><mrow><mrow><mo>|</mo></mrow><msub><mi>γ</mi><mi>ν</mi></msub><mo>-</mo><msub><mi>γ</mi><mi>EM</mi></msub><mrow><mo>|</mo><mo>&lt;</mo><mn>5.5</mn><mo>×</mo></mrow><msup><mn>10</mn><mrow><mo>-</mo><mn>2</mn></mrow></msup></mrow></math> , after assuming time difference of 175 days between neutrino and photon arrival times.

Sibel Boran

India

Shantanu Desai

Constraints on differential Shapiro delay between neutrinos and photons from IceCube-170922A

We calculate the total galactic Shapiro delay to the Crab pulsar by including the contributions from the dark matter as well as baryonic matter along the line of sight. The total delay due to dark matter potential is about 3.4 days. For baryonic matter, we included the contributions from both the bulge and the disk, which are approximately 0.12 and 0.32 days respectively. The total delay from all the matter distribution is therefore 3.84 days. We also calculate the limit on violations of Weak equivalence principle by using observations of ânano-shotâ giant pulses from the Crab pulsar with time-delay &lt;0.4 Â ns, as well as using time differences between radio and optical photons observed from this pulsar. Using the former, we obtain a limit on violation of Weak equivalence principle in terms of the PPN parameter ÎÎ³&lt;2.41Ã10-15 . From the time-difference between simultaneous optical and radio observations, we get ÎÎ³&lt;1.54Ã10-9 . We also point out differences in our calculation of Shapiro delay and that from two recent papersÂ (Yang and Zhang, Phys Rev D 94(10):101501, 2016 ; Zhang and Gong, Astrophys J 837:134, 2017 ), which used the same observations to obtain a corresponding limit on ÎÎ³ .

Galactic Shapiro delay to the Crab pulsar and limit on weak equivalence principle violation