328 research outputs found
Spinning gravitating objects in the effective field theory in the post-Newtonian scheme
We introduce a formulation for spinning gravitating objects in the effective
field theory in the post-Newtonian scheme in the context of the binary inspiral
problem. We aim at an effective action, where all field modes below the orbital
scale are integrated out. We spell out the relevant degrees of freedom, in
particular the rotational ones, and the associated symmetries. Building on
these symmetries, we introduce the minimal coupling part of the point particle
action in terms of gauge rotational variables, and construct the spin-induced
nonminimal couplings, where we obtain the leading order couplings to all orders
in spin. We specify the gauge for the rotational variables, where the
unphysical degrees of freedom are eliminated already from the Feynman rules,
and all the orbital field modes are integrated out. The equations of motion of
the spin can be directly obtained via a proper variation of the action, and
Hamiltonians may be straightforwardly derived. We implement this effective
field theory for spin to derive all spin dependent potentials up to
next-to-leading order to quadratic level in spin, namely up to the third
post-Newtonian order for rapidly rotating compact objects. In particular, the
proper next-to-leading order spin-squared potential and Hamiltonian for generic
compact objects are also derived. For the implementations we use the
nonrelativistic gravitational field decomposition, which is found here to
eliminate higher-loop Feynman diagrams also in spin dependent sectors, and
facilitates derivations. This formulation for spin is thus ideal for treatment
of higher order spin dependent sectors.Comment: 47 pages, 4 figures, publishe
Equivalence of ADM Hamiltonian and Effective Field Theory approaches at next-to-next-to-leading order spin1-spin2 coupling of binary inspirals
The next-to-next-to-leading order spin1-spin2 potential for an inspiralling
binary, that is essential for accuracy to fourth post-Newtonian order, if both
components in the binary are spinning rapidly, has been recently derived
independently via the ADM Hamiltonian and the Effective Field Theory
approaches, using different gauges and variables. Here we show the complete
physical equivalence of the two results, thereby we first prove the equivalence
of the ADM Hamiltonian and the Effective Field Theory approaches at
next-to-next-to-leading order with the inclusion of spins. The main difficulty
in the spinning sectors, which also prescribes the manner in which the
comparison of the two results is tackled here, is the existence of redundant
unphysical spin degrees of freedom, associated with the spin gauge choice of a
point within the extended spinning object for its representative worldline.
After gauge fixing and eliminating the unphysical degrees of freedom of the
spin and its conjugate at the level of the action, we arrive at curved
spacetime generalizations of the Newton-Wigner variables in closed form, which
can also be used to obtain further Hamiltonians, based on an Effective Field
Theory formulation and computation. Finally, we make use of our validated
result to provide gauge invariant relations among the binding energy, angular
momentum, and orbital frequency of an inspiralling binary with generic compact
spinning components to fourth post-Newtonian order, including all known sectors
up to date.Comment: 44 pages; v2: publishe
Next-to-leading order gravitational spin1-spin2 coupling with Kaluza-Klein reduction
We use the recently proposed Kaluza-Klein (KK) reduction over the time
dimension, within an effective field theory (EFT) approach, to calculate the
next to leading order (NLO) gravitational spin1-spin2 interaction between two
spinning compact objects. It is shown here that to NLO in the spin1-spin2
interaction, the reduced KK action within the stationary approximation is
sufficient to describe the gravitational interaction, and that it simplifies
calculation substantially. We also find here that the gravito-magnetic vector
field defined within the KK decomposition of the metric mostly dominates the
mediation of the interaction. Our results coincide with those calculated in the
ADM Hamiltonian formalism, and we provide another explanation for the
discrepancy with the result previously derived within the EFT approach, thus
demonstrating clearly the equivalence of the ADM Hamiltonian formalism and the
EFT action approach.Comment: 12 pages, revtex4-1, 3 figures; v2: reference added; v3: edited,
section 3 elaborated; v4: publishe
Tectono-metamorphic history of the ophiolitic Lento unit (northern Corsica): evidences for the complexity of accretion-exhumation processes in a fossil subduction system
The Alpine Corsica (Corsica Island, France) is characterized by a stack of continent- and ocean-derived tectonic units, known as Schistes Lustres complex. This complex is affected by deformation and metamorphic imprint achieved during Late Cretaceous – Early Tertiary subduction- related processes connected with the closure of the Ligure-Piemontese oceanic basin and subsequent continental collision. In the Schistes Lustres complex, the Lento oceanic unit is characterized by four deformation phases, from D1 to D4 phase. The D1 phase, characterized by blueschist metamorphism, is regarded as related to coherent underplating in a subduction zone at a depth of about 25-30 km. The subsequent deformation phases can be referred to exhumation history, as suggested by the continuous decrease of metamorphic conditions. The transition from accretion to exhumation is represented by the D2 phase, achieved during the development of a duplex structure of accreted units. The D3 phase is in turn achieved by a further horizo..
Reducing cavity-pulling shift in Ramsey-operated compact clocks
We describe a method to stabilize the amplitude of the interrogating
microwave field in compact atomic clocks working in a Ramsey approach. In this
technique, we take advantage of the pulsed regime to use the atoms themselves
as microwave amplitude discriminators. Specifically, in addition to the
dependence on the microwave detuning, the atomic signal after the Ramsey
interrogation acquires a dependence on the microwave pulse area (amplitude
times duration) that can be exploited to implement an active stabilization of
the microwave field amplitude, in a similar way in which the Ramsey clock
signal is used to lock the local oscillator frequency to the atomic reference.
This stabilization results in a reduced sensitivity of the clock frequency to
microwave amplitude fluctuations that are transferred to the atoms through the
cavity-pulling effect. The proposed technique is then effective to improve the
clock stability and drift on medium and long term. We demonstrate the method
for a vapor-cell clock working with a hot sample of atoms but it can be
extended to cold-atom compact clocks.Comment: Accepted for publication by IEEE UFFC on April 16th 201
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