The Turbulence in incompressible fluid is represented as a Field Theory in 3 dimensions. There is no time involved, so this is intended to describe stationary limit of the Hopf functional.
The basic fields are Clebsch variables defined modulo gauge transformations (symplectomorphisms).
Explicit formulas for gauge invariant Clebsch measure in space of Generalized Beltrami Flow...
Recently it was realized that in certain situations folded strings are created at an instant. Since they violate the average null energy condition they lead to fascinating effects in Cosmology and black holes.
String Theory is believed to have more than $10^{500}$ possible compactifications to four dimensions, leading to de Sitter universes whose physics resembles that of our universe. This is often invoked as supporting the ``anthropic principle'': our universe is but one of this multitude of universes (multiverse), and the physical parameters we observe in our universe are selected by requiring...
We study the holographic phase transition of the radion field in a five-dimensional warped model which includes a scalar potential with a power-like behavior. We consider Kaluza-Klein (KK) resonances with masses $m_{\rm KK}$ at the TeV scale or beyond. The backreaction of the radion field on the gravitational metric is taken into account by using the superpotential formalism. The...
We present our recent work that is the description of a gravitational theory as a gague theory on a covariant noncommutative space. First, we remind the most basics of the translation of gravity theories to the gauge theory language and also the tools we use to construct gauge theories on noncommutative spaces. Then, we describe the construction of the covariant noncommutative space, that is a...
It is since 1966, with the paper of DeWitt, that there is great interest in the interplay between the theory of gravitation and superconductivity. In the following years, a lot of theoretical papers about this topic have been produced, until Podkletnov and Nieminem declared to have observed a gravitational shielding in a disk of YBaCuO. Of course, after the publication of this paper, other...
We analyze the stability at one-loop of open string models in four-dimensional Minkowski space, where N=2 supersymmetry is spontaneously broken. In the region of moduli space where the supersymmetry breaking scale is lower than all other scales, we identify vanishing minima of the one-loop effective potential, up to exponentially small corrections. In these backgrounds, the spectrum satisfies...
In this talk I will present a fundamental theory of the QCD axion: all couplings flow to zero in the infinite energy limit (realizing the totally asymptotically free scenario) and the Peccei-Quinn (PQ) scale $f_a$ is dynamically generated by quantum effects. This theory is highly predictive as the axion sector only features few free parameters: $f_a$ and the QCD gauge coupling. The PQ phase...
We need Dark Matter to explain lack of gravitational potentials in present and early Universe at various spatial scales. So it must participate in gravitational interactions. Gravity can even produce the Dark Matter while the Universe expands. What changes if the Dark Matter is a substence with non-minimal coupling to gravity? Actually, a variety of options ranging from 'gravity can destroy...
I will present an overview of primordial black holes as dark matter candidates, across a wide range of masses and detection methods.
The KOTO experiment has reported an excess of $K_L\to\pi^0\nu\bar\nu$ events above the standard model prediction, in tension with the Grossman--Nir bound. The GN bound heavily constrains new physics interpretations of an excess in this channel, but another possibility is that the observed events originate from a different process entirely: a decay of the form $K_L\to\pi^0X$, where $X$ denotes...
In the age of gravitational wave astronomy, the possibility that some of the black holes in the universe have a primordial, rather than stellar origin, and that they might be a non-negligible fraction of the cosmological dark matter, is quite intriguing. I will review the status of the field, and comment on search strategies and future prospects for detection across many decades in black hole...
Microlensing of stars places significant constraints on sub-planetary mass compact objects, including primordial black holes, as dark matter candidates. However, when the Einstein radius of the lens in the source plane is smaller than the size of the light source, amplification is strongly suppressed, making it difficult to constrain lenses with a mass below ~10^{-10} solar masses, i.e....
A dark QCD sector is a relatively minimal extension of the Standard Model that admits Dark Matter (DM) candidates, but requires no portal to the SM sector beyond gravitational interactions:
A ``nightmare scenario'' for DM detection.
We consider a minimal dark sector gauged under $SU(N)$ with a single flavor of light, vector-like dark quark.
In the large-$N$ limit, this single-flavor...
