32,012 research outputs found
Can a millicharged dark matter particle emit an observable gamma-ray line?
If a gamma-ray line is observed in the near future, it will be important to
determine what kind of dark matter (DM) particle could be at its origin. We
investigate the possibility that the gamma-ray line would be induced by a slow
DM particle decay associated to the fact that the DM particle would not be
absolutely neutral. A "millicharge" for the DM particle can be induced in
various ways, in particular from a kinetic mixing interaction or through the
Stueckelberg mechanism. We show that such a scenario could lead in specific
cases to an observable gamma-ray line. This possibility can be considered in a
systematic model-independent way, by writing down the corresponding effective
theory. This allows for a multi-channel analysis, giving in particular upper
bounds on the intensity of the associated gamma-ray line from cosmic rays
emission. Our analysis includes the possibility that in the two-body decay the
photon is accompanied with a neutrino. We show that, given the stringent
constraints which hold on the millicharge of the neutrinos, this is not an
option, except if the DM particle mass lies in the very light KeV-MeV range,
allowing for a possibility of explanation of the recently claimed, yet to be
confirmed, ~3.5KeV X-ray line.Comment: 10 pages, references and one figure presenting the bounds holding on
the dark charge in the kinetic mixing case adde
New Search for Monochromatic Neutrinos from Dark Matter Decay
From data recently reported from the IceCube telescope, we derive new bounds
on the monochromatic neutrino signal produced from dark matter particle decays.
In the few TeV to tens of TeV energy range, these bounds turn out to be better
than previous limits by more than an order of magnitude. As a result, intensity
constraints on neutrino lines at energies above a few TeV are now comparable to
those on gamma-ray lines. From the same data sample, we also perform a detailed
search for a neutrino line, showing that there is no significant hint for such
a signal.Comment: 12 pages, 13 figures. Tabulated results attached among the source
files (Appendix_D_Table.dat
On a conjecture of Dekking : The sum of digits of even numbers
Let and denote by the sum-of-digits function in base . For
consider # \{0 \le n < N : \;\;s_q(2n) \equiv j \pmod q \}.
In 1983, F. M. Dekking conjectured that this quantity is greater than
and, respectively, less than for infinitely many , thereby claiming an
absence of a drift (or Newman) phenomenon. In this paper we prove his
conjecture.Comment: 6 pages, accepted by JTN
Learning to bid in revenue-maximizing auctions
We consider the problem of the optimization of bidding strategies in
prior-dependent revenue-maximizing auctions, when the seller fixes the reserve
prices based on the bid distributions. Our study is done in the setting where
one bidder is strategic. Using a variational approach, we study the complexity
of the original objective and we introduce a relaxation of the objective
functional in order to use gradient descent methods. Our approach is simple,
general and can be applied to various value distributions and
revenue-maximizing mechanisms. The new strategies we derive yield massive
uplifts compared to the traditional truthfully bidding strategy
Cantor sets and cyclicity in weighted Dirichlet spaces
We treat the problem of characterizing the cyclic vectors in the weighted
Dirichlet spaces, extending some of our earlier results in the classical
Dirichlet space. The absence of a Carleson-type formula for weighted Dirichlet
integrals necessitates the introduction of new techniques
Did the European Free Movement of Persons and Residence Directive Change Migration Patterns within the EU? A First Glance
Niederlassungsrecht, EU-Recht, Freizügigkeit, Mobilität, Europäische Wirtschafts- und Währungsunion, Freedom of establishment, Community law, Freedom of movement , Mobility, European Economic and Monetary Union
Baseband Radio over Fiber Aided Millimeter-Wave Distributed Antenna for Optical/Wireless Integration
A Baseband Radio Over Fiber (BROF) architecture is proposed, where upto four Radio Frequency (RF) carriers can be generated, while using the heterodyne photo-detection of only two optical signals. This proposed BROF architecture has a star-like structure and it is composed of six Radio Access Units (RAUs), where data is transmitted from the Central Unit (CU) to the Base Station (BS) and from the BS to the RAU over a distance of 20 Km and 0.3 Km, respectively, at a rate of 768 Mbps. The performance of the system supporting four carrier frequencies drops by at most 1dB, at a BER of 10-9, compared to conventional heterodyne photo-detection
- …