[astroseminar at Sapienza] Gravity theory webinar Mon Jan 25th: Katsuki Aoki (Yakawa Institute) "Non-linearly ghost-free higher curvature gravity"

[Paolo Pani]

Announcement of the next gravity-theory webinar:

*Katsuki Aoki* (Yukawa Institute for Theoretical Physics, Kyoto University)
*Monday, Jan 25th, h11:00am*

Title: *Non-linearly ghost-free higher curvature gravity*

Abstract: We find unitary and local theories of higher curvature gravity in
the vielbein formalism, known as the Poincaré gauge theory by utilizing the
equivalence to the ghost-free massive bigravity. We especially focus on
three and four dimensions but extensions into a higher dimensional
spacetime are straightforward. In three dimensions, a quadratic gravity
L=R+T^2+R^2, where R is the curvature and T is the torsion with indices
omitted, is shown to be equivalent to zwei-dreibein gravity and free from
the ghost at fully non-linear orders. In a special limit, new massive
gravity is recovered. When the model is applied to the AdS/CFT
correspondence, unitarity both in the bulk theory and in the boundary
theory implies that the torsion must not vanish. On the other hand, in four
dimensions, the absence of ghost at non-linear orders requires an infinite
number of higher curvature terms, and these terms can be given by a
schematic form R/(1+R/alpha m^2)R where m is the mass of the massive spin-2
mode originating from the higher curvature terms and alpha is an additional
parameter that determines the amplitude of the torsion. We also provide
another four-dimensional ghost-free higher curvature theory that contains a
massive spin-0 mode as well as the massive spin-2 mode.


Zoom link:
https://uniroma1.zoom.us/j/81283707469?pwd=SzkyMk5jRm0xcEN3WE5MYVh1RVFtQT09
ID meeting: 812 8370 7469
Passcode: 915450

List of the next gravity-theory webinars (calendar available here:
https://calendar.google.com/calendar/u/1?cid=Y191MGo3bG9pYzE1bjBxdGFhN3A4MTlzNDg2Y0Bncm91cC5jYWxlbmRhci5nb29nbGUuY29t
)

08/02/2021 h12:00   Jonas P. Pereira (Nicolaus Copernicus Astronomical
Center, Warsaw PL):  "Probing elastic quark phases in hybrid stars"
15/03/2021 h12:00   Danny Laghi & Gregorio Carullo (Pisa University, IT):
                                  "TBA"
24/03/2021 h16:00   William East (Perimeter Institute, CAN):
                                          "Black-hole mergers in
Einstein-scalar-Gauss-Bonnet gravity"
14/04/2021 h16:00   Jorge Rocha (ISCTE, PT):
                                               "Recent developments toward
the resolution of the information-loss paradox"

Cheers,
Paolo


-- 
Paolo Pani
Associate Professor
ERC StG Fellow, DarkGRA project
Junior Fellow, Scuola Superiore di Studi Avanzati Sapienza

Physics Department (Marconi Building), 3rd floor, room 334
Sapienza University of Rome
Piazzale Aldo Moro 5 - 00185 Rome (Italy)
+39 06 4991 4472 (int 24472)

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