Modern optical atomic clocks along with the optical fiber technology currently being developed can measure the geoid, which is the equipotential surface that extends the mean sea level on continents, to a precision that competes with existing technol
ogy. In this proceeding, we point out that atomic clocks have the potential to not only map the sea level surface on continents, but also look at variations of the geoid as a function of time with unprecedented timing resolution. The local time series of the geoid has a plethora of applications. These include potential improvement in the predictions of earthquakes and volcanoes, and closer monitoring of ground uplift in areas where hydraulic fracturing is performed.
Microlensing observations toward globular clusters could be very useful to probe their low mass star and brown dwarf content. Using the large set of microlensing events detected so far toward the Galactic centre we investigated whether for some of th
e observed events the lenses are located in the Galactic globular clusters. Indeed, we found that in four cases some events might be due to lenses located in the globular clusters themselves. Moreover, we discuss a microlensing event found in M22. Using the adaptive optics system NACO at ESO VLT it was possible to identify the lens, which turned out to be a low mass star of about 0.18 solar masses in the globular cluster M22 itself.
Microlensing started with the seminal paper by Paczynski in 1986, first with observations towards the Large Magellanic Cloud and the galactic bulge. Since then many other targets have been observed and new applications have been found. In particular,
it turned out to be a powerful method to detect planets in our galaxy and even in the nearby M31. Here, we will present some results obtained so far by microlensing without being, however, exhaustive.
The nature of the dark energy is still a mystery and several models have been proposed to explain it. Here we consider a phenomenological model for dark energy decay into photons and particles as proposed by Lima (J. Lima, Phys. Rev. D 54, 2571 (1996
)). He studied the thermodynamic aspects of decaying dark energy models in particular in the case of a continuous photon creation and/or disruption. Following his approach, we derive a temperature redshift relation for the CMB which depends on the effective equation of state $w_{eff}$ and on the adiabatic index $gamma$. Comparing our relation with the data on the CMB temperature as a function of the redshift obtained from Sunyaev-Zeldovich observations and at higher redshift from quasar absorption line spectra, we find $w_{eff}=-0.97 pm 0.034$, adopting for the adiabatic index $gamma=4/3$, in good agreement with current estimates and still compatible with $w_{eff}=-1$, implying that the dark energy content being constant in time.
We present an analysis of the large set of microlensing events detected so far toward the Galactic center with the purpose of investigating whether some of the dark lenses are located in Galactic globular clusters. We find that in four cases some eve
nts might indeed be due to lenses located in the globular clusters themselves. We also give a rough estimate for the average lens mass of the events being highly aligned with Galactic globular cluster centers and find that, under reasonable assumptions, the deflectors could most probably be either brown dwarfs, M-stars or stellar remnants.
In this note we perform an analysis of the large set of microlensing events detected so far toward the Galactic center with the purpose of investigating whether some of the dark lenses are located in Galactic globular clusters. We find that in four c
ases some events might indeed be due to lenses located in the globular clusters themselves. We also give a rough estimate for the average lens mass of the subset of events being highly aligned with Galactic globular cluster centers and find that, under reasonable assumptions, the deflectors could most probably be either brown dwarfs, M-stars or stellar remnants.
