599 research outputs found
Nonthermal Two Component Dark Matter Model for Fermi-LAT -ray excess and 3.55 keV X-ray Line
A two component model of nonthermal dark matter is formulated to
simultaneously explain the Fermi-LAT results indicating a -ray excess
observed from our Galactic Centre in the 1-3 GeV energy range and the detection
of an X-ray line at 3.55 keV from extragalactic sources. Two additional
Standard Model singlet scalar fields and are introduced. These
fields couple among themselves and with the Standard Model Higgs doublet .
The interaction terms among the scalar fields, namely , and , are
constrained by the application of a discrete symmetry which breaks softly to a remnant
symmetry. This residual discrete symmetry is
then spontaneously broken through an MeV order vacuum expectation value of
the singlet scalar field . The resultant physical scalar spectrum has the
Standard Model like Higgs as with GeV, a moderately heavy scalar with and a light
with keV. There is only tiny mixing between
and as well as between
and . The lack of importance of domain wall formation in the
present scenario from the spontaneous breaking of the discrete symmetry
, provided MeV, is pointed out. We
find that our proposed two component dark matter model is able to explain
successfully both the above mentioned phenomena the Fermi-LAT observed
-ray excess (from the decay mode) and the observation of the X-ray line (from the decay channel
) by the XMM-Newton observatory.Comment: 11 eps Figures, 2 Tables, 32 Pages. Minor addition in Abstract.
Inclusion in Section 1 of discussion of earlier attempts to explain the
concerned phenomena by astrophysical processes. Extension of discussion in
Section 6 to the case of a steeper dark matter density profile. Results
unchanged. Version accepted for publication in JHE
Dwarf Galaxy -excess and 3.55 keV X-ray Line In A Nonthermal Dark Matter Model
Recent data from Reticulum II (RetII) require the energy range of the
FermiLAT -excess to be GeV. We adjust our unified
nonthermal Dark Matter (DM) model to accommodate this. We have two extra
scalars beyond the Standard Model to also explain 3.55 keV X-ray line. Now the
mass of the heavier of them has to be increased to lie around 250 GeV, while
that of the lighter one remains at 7.1 keV. This requires a new seed mechanism
for the -excess and new Boltzmann equations for the generation of the
DM relic density. All concerned data for RetII and the X-ray line can now be
fitted well and consistency with other indirect limits attained.Comment: 8 eps figures, 1 Table, 7 pages. The paper has been completely
rewritten with additional references and discussions of indirect constraints
from AMS-02 and ANTARES data. Basic results remain unchanged. Version
accepted for publication in Europhysics Letter
Possible explanation of indirect gamma ray signatures from hidden sector fermionic dark matter
We propose the existence of a hidden or dark sector besides the standard
model (SM) of particle physics, whose members (both fermionic and bosonic) obey
a local SU(2) gauge symmetry while behaving like a singlet under the
SM gauge group. However, the fermiomic fields of the dark sector also possess
another global U(1) symmetry which remains unbroken. The local
SU(2) invariance of the dark sector is broken spontaneously when a
scalar field in this sector acquires a vacuum expectation value (VEV) and
thereby generating masses to the dark gauge bosons and dark fermions charged
under the SU(2). The lightest fermion in this dark SU(2)
sector can be a potential dark matter candidate. We first examine the viability
of the model and constrain the model parameter space by theoretical constraints
such as vacuum stability and by the experimental constraints such as PLANCK
limit on relic density, LHC data, limits on spin independent scattering
cross-section from dark matter direct search experiments etc. We then
investigate the gamma rays from the pair annihilation of the proposed dark
matter candidate at the Galactic Centre region. We also extend our calculations
of gamma rays flux for the case of dwarf galaxies and compare the signatures of
gamma rays obtained from these astrophysical sites.Comment: 33 pages, 16 figures, title changed, major revisio
Width of Non-deterministic Automata
International audienceWe introduce a measure called width, quantifying the amount of nondeterminism in automata. Width generalises the notion of good-for-games (GFG) automata, that correspond to NFAs of width 1, and where an accepting run can be built on-the-fly on any accepted input. We describe an incremental determinisation construction on NFAs, which can be more efficient than the full powerset determinisation, depending on the width of the input NFA. This construction can be generalised to infinite words, and is particularly well-suited to coBüchi automata in this context. For coBüchi automata, this procedure can be used to compute either a deterministic automaton or a GFG one, and it is algorithmically more efficient in this last case. We show this fact by proving that checking whether a coBüchi automaton is determinisable by pruning is NP-complete. On finite or infinite words, we show that computing the width of an automaton is PSPACE-hard. 1 Introduction Determinisation of non-deterministic automata (NFAs) is one of the cornerstone problems of automata theory, with countless applications in verification. There is a very active field of research for optimizing or approximating determinisation, or circumventing it in contexts like inclusion of NFA or Church Synthesis. Indeed, determinisation is a costly operation, as the state space blow-up is in O(2 n) on finite words, O(3 n) for coBüchi automata [16], and 2 O(n log(n)) for Büchi automata [17]. If A and B are NFAs, the classical way of checking the inclusion L(A) ⊆ L(B) is to determinise B, complement it, and test emptiness of L(A) ∩ L(B). To circumvent a full determinisation, the recent algorithm from [3] proved to be very efficient, as it is likely to explore only a part of the powerset construction. Other approaches use simulation games to approximate inclusion at a cheaper cost, see for instance [8]. Another approach consists in replacing determinism by a weaker constraint that suffices in some particular context. In this spirit, Good-for-Games automata (GFG for short) were introduced in [9], as a way to solve the Church synthesis problem. This problem asks, given a specification L, typically given by an LTL formula, over an alphabet of inputs and outputs, whether there is a reactive system (transducer) whose behaviour is included in L. The classical solution computes a deterministic automaton for L, and solves a game defined on this automaton. It turns out that replacing determinism by the weaker constraint of being GFG is sufficient in this context. Intuitively, GFG automata are non-deterministic * This work was supported by the grant PALSE Impulsion
Computing the Width of Non-deterministic Automata
International audienceWe introduce a measure called width, quantifying the amount of nondetermin-ism in automata. Width generalises the notion of good-for-games (GFG) automata, that correspond to NFAs of width 1, and where an accepting run can be built on-the-fly on any accepted input. We describe an incremental determinisation construction on NFAs, which can be more efficient than the full powerset determinisation, depending on the width of the input NFA. This construction can be generalised to infinite words, and is particularly well-suited to coBüchi automata. For coBüchi automata, this procedure can be used to compute either a deterministic automaton or a GFG one, and it is algorithmically more efficient in the last case. We show this fact by proving that checking whether a coBüchi automaton is determinisable by pruning is NP-complete. On finite or infinite words, we show that computing the width of an automaton is EXPTIME-complete. This implies EXPTIME-completeness for multipebble simulation games on NFAs
Two component WIMP-FImP dark matter model with singlet fermion, scalar and pseudo scalar
We explore a two component dark matter model with a fermion and a scalar. In
this scenario the Standard Model (SM) is extended by a fermion, a scalar and an
additional pseudo scalar. The fermionic component is assumed to have a global
and interacts with the pseudo scalar via Yukawa
interaction while a symmetry is imposed on the other component
-- the scalar. These ensure the stability of both the dark matter components.
Although the Lagrangian of the present model is CP conserving, however the CP
symmetry breaks spontaneously when the pseudo scalar acquires a vacuum
expectation value (VEV). The scalar component of the dark matter in the present
model also develops a VEV on spontaneous breaking of the
symmetry. Thus the various interactions of the dark sector and the SM sector
are progressed through the mixing of the SM like Higgs boson, the pseudo scalar
Higgs like boson and the singlet scalar boson. We show that the observed gamma
ray excess from the Galactic Centre, self-interaction of dark matter from
colliding clusters as well as the 3.55 keV X-ray line from Perseus, Andromeda
etc. can be simultaneously explained in the present two component dark matter
model.Comment: 35 pages, 5 figure
Wilson flow with naive staggered quarks
Scale setting for QCD with two flavours of staggered quarks is examined using
Wilson flow over a factor of four change in both the lattice spacing and the
pion mass. The statistics needed to keep the errors in the flow scale fixed is
found to increase approximately as the inverse square of the lattice spacing.
Tree level improvement of the scales t_0 and w_0 is found to be useful in most
of the range of lattice spacings we explore. The scale uncertainty due to
remaining lattice spacing effects is found to be about 3%. The ratio
w_0/\sqrt{t_0} is N_f dependent and we find its continuum limit to be 1.106 \pm
0.007 (stat) \pm 0.005 (syst) for m_\pi w_0 \simeq 0.3
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