Dynamical boson stars

An exceptional G(2) extension of the Standard Model from the correspondence with Cayley-Dickson algebras automorphism groups

In this article I propose a new criterion to extend the Standard Model of particle physics from a straightforward algebraic conjecture: the symmetries of physical microscopic forces originate from the automorphism groups of main Cayley-Dickson algebras, from complex numbers to octonions and sedenions. This correspondence leads to a natural enlargement of the Standard Model color sector, from a SU(3) gauge group to an exceptional Higgs-broken G(2) group, following the octonionic automorphism relation guideline. In this picture, an additional ensemble of massive G(2)-gluons emerges, which is separated from the particle dynamics of the Standard Model.

General Relativistic Decoherence with Applications to Dark Matter Detection

Quantum mechanics allows for states in macroscopic superpositions, but they ordinarily undergo rapid decoherence due to interactions with their environment. A system that only interacts gravitationally, such as an arrangement of dark matter (DM), may exhibit slow decoherence. In this Letter, we compute the decoherence rate of a quantum object within general relativity, focusing on superposed metric oscillations; a rare quantum general relativistic result. For axion DM in a superposition of the field's phase, we find that DM in the Milky Way is robust against decoherence, while a spatial superposition is not. This novel phase behavior may impact direct detection experiments.

GW190521 as a Merger of Proca Stars: A Potential New Vector Boson of 8.7×10^{-13} eV

Advanced LIGO-Virgo have reported a short gravitational-wave signal (GW190521) interpreted as a quasicircular merger of black holes, one at least populating the pair-instability supernova gap, that formed a remnant black hole of M_{f}∼142  M_{⊙} at a luminosity distance of d_{L}∼5.3  Gpc. With barely visible pre-merger emission, however, GW190521 merits further investigation of the pre-merger dynamics and even of the very nature of the colliding objects. We show that GW190521 is consistent with numerically simulated signals from head-on collisions of two (equal mass and spin) horizonless vector boson stars (aka Proca stars), forming a final black hole with M_{f}=231_{-17}^{+13}  M_{⊙}, located at a distance of d_{L}=571_{-181}^{+348}  Mpc. This provides the first demonstration of close degeneracy between these two theoretical models, for a real gravitational-wave event. The favored mass for the ultralight vector boson constituent of the Proca stars is μ_{V}=8.72_{-0.82}^{+0.73}×10^{-13}  eV. Confirmation of the Proca star interpretation, which we find statistically slightly preferred, would provide the first evidence for a long sought dark matter particle.

Gravimeter Search for Compact Dark Matter Objects Moving in the Earth

Dark matter could be composed of compact dark objects (CDOs). These objects may interact very weakly with normal matter and could move freely inside the Earth. A CDO moving in the inner core of the Earth will have an orbital period near 55 min and produce a time-dependent signal in a gravimeter. Data from superconducting gravimeters rule out such objects moving inside the Earth unless their mass m_{D} and or orbital radius a are very small so that m_{D}a<1.2×10^{-13}M_{⊕}R_{⊕}. Here, M_{⊕} and R_{⊕} are the mass and radius of the Earth, respectively.

Nonlinear Dynamics of Spinning Bosonic Stars: Formation and Stability

We perform numerical evolutions of the fully nonlinear Einstein (complex, massive) Klein-Gordon and Einstein (complex) Proca systems, to assess the formation and stability of spinning bosonic stars. In the scalar (vector) case these are known as boson (Proca) stars. Firstly, we consider the formation scenario. Starting with constraint-obeying initial data, describing a dilute, axisymmetric cloud of spinning scalar or Proca field, gravitational collapse toward a spinning star occurs, via gravitational cooling. In the scalar case the formation is transient, even for a nonperturbed initial cloud; a nonaxisymmetric instability always develops ejecting all the angular momentum from the scalar star. In the Proca case, by contrast, no instability is observed and the evolutions are compatible with the formation of a spinning Proca star. Secondly, we address the stability of an existing star, a stationary solution of the field equations. In the scalar case, a nonaxisymmetric perturbation develops, collapsing the star to a spinning black hole. No such instability is found in the Proca case, where the star survives large amplitude perturbations; moreover, some excited Proca stars decay to, and remain as, fundamental states. Our analysis suggests bosonic stars have different stability properties in the scalar (vector) case, which we tentatively relate to its toroidal (spheroidal) morphology. A parallelism with instabilities of spinning fluid stars is briefly discussed.

Multioscillating Boson Stars

We propose that stable boson stars generically fall within an infinite-parameter family of solutions that oscillate on any number of noncommensurate frequencies. We numerically construct two-frequency solutions and explore their parameter space. These solutions merge with the standard boson star family in the limit where the nondominating frequencies are turned off. We find that, for a fixed energy, these two-frequency solutions can differ considerably in size from standard boson stars.