1,607 research outputs found
The Pure State Space of Quantum Mechanics as Hermitian Symmetric Space
The pure state space of Quantum Mechanics is investigated as Hermitian
Symmetric Kaehler manifold. The classical principles of Quantum Mechanics
(Quantum Superposition Principle, Heisenberg Uncertainty Principle, Quantum
Probability Principle) and Spectral Theory of observables are discussed in this
non linear geometrical context.Comment: 18 pages, no figure
Multi-Component Dark Matter
We explore multi-component dark matter models where the dark sector consists
of multiple stable states with different mass scales, and dark forces coupling
these states further enrich the dynamics. The multi-component nature of the
dark matter naturally arises in supersymmetric models, where both R parity and
an additional symmetry, such as a , is preserved. We focus on a particular
model where the heavier component of dark matter carries lepton number and
annihilates mostly to leptons. The heavier component, which is essentially a
sterile neutrino, naturally explains the PAMELA, ATIC and synchrotron signals,
without an excess in antiprotons which typically mars other models of weak
scale dark matter. The lighter component, which may have a mass from a GeV to a
TeV, may explain the DAMA signal, and may be visible in low threshold runs of
CDMS and XENON, which search for light dark matter.Comment: 4 pages, no figures. v2: paper shortened to letter length; modified
dark matter spectru
Dark matter in natural supersymmetric extensions of the Standard Model
We explore the dark matter sector in extensions of the Minimal Supersymmetric
Standard Model (MSSM) that can provide a good fit to the PAMELA cosmic ray
positron excess, while at the same time addressing the little hierarchy problem
of the MSSM. Adding a singlet Higgs superfield, S, can account for the observed
positron excess, as recently discussed in the literature, but we point out that
it requires a fine-tuned choice for the parameters of the model. We find that
including an additional singlet allows both a reduction of the weak-scale
fine-tuning, and an interpretation of the cosmic ray observations in terms of
dark matter annihilations in the galactic halo. Our setup contains a light
axion, but does not require light CP-even scalars in the spectrum.Comment: 26 pages, 8 figures, references adde
Supersymmetric Extension of the Minimal Dark Matter Model
The minimal dark matter model is given a supersymmetric extension. A super
SU(2)L quintuplet is introduced with its fermionic neutral component still
being the dark matter, the dark matter particle mass is about 19.7 GeV. Mass
splitting among the quintplet due to supersymmetry particles is found to be
negligibly small compared to the electroweak corrections. Other properties of
this supersymmetry model are studied, it has the solutions to the PAMELA and
Fermi-LAT anomaly, the predictions in higher energies need further experimental
data to verify.Comment: 14 pages, 7 figures, accepted for publication in Chinese Physics C,
typos correcte
Recent developments in theory and phenomenology of Dark Matter
Dark Matter constitutes more than 80% of the total amount of
matter in the Universe, yet almost nothing is known about its nature. A powerful investigation technique is that of searching for the products of annihilations of Dark Matter particles in the galactic halo, on top of the ordinary cosmic rays. Recent data from the PAMELA and FERMI satellites and a number of balloon experiment have reported unexpected excesses in the measured fluxes of cosmic rays. Are these the first direct evidences for Dark Matter? If yes, which DM models and candidates can explain these anomalies (in terms of annihilations) and what do they imply for future searches and model building? What are the constraints from gamma-rays measurements and cosmology
Dark Matter searches: A theoretical perspective
In an era of promising experimental searches, Dark Matter theorists are diversifying their portfolio, adding assets different from the time-honored SuperSymmetric neutralino. I pick and briefly discuss a few new directions in model
building and in phenomenology: Minimal Dark Matter, Asymmetric Dark Matter and Secluded Dark Matter (Report numbers: CERN-PH-TH/2012-081, SACLAY–T12/026)
When CoGeNT met PAMELA
If the excess events from the CoGeNT experiment arise from elastic
scatterings of a light dark matter off the nuclei, crossing symmetry implies
non-vanishing annihilation cross-sections of the light dark matter into
hadronic final states inside the galactic halo, which we confront with the
anti-proton spectrum measured by the PAMELA collaboration. We consider two
types of effective interactions between the dark matter and the quarks: 1)
contact interactions from integrating out heavy particles and 2) long-range
interactions due to the electromagnetic properties of the dark matter. The lack
of excess in the anti-proton spectrum results in tensions for a scalar and, to
a less extent, a vector dark matter interacting with the quarks through the
Higgs portal.Comment: 15 pages, 3 figures. Updated references and included effects of solar
modulatio
Symmetryless Dark Matter
It is appealing to stabilize dark matter by the same discrete symmetry that
is used to explain the structure of quark and lepton mass matrices. However, to
generate the observed fermion mixing patterns, any flavor symmetry must
necessarily be broken, rendering dark matter unstable. We study singlet,
doublet and triplet SU(2) multiplets of both scalar and fermion dark matter
candidates and enumerate the conditions under which no d < 6 dark matter decay
operators are generated even in the case if the flavor symmetry is broken to
nothing. We show that the VEVs of flavon scalars transforming as higher
multiplets (e.g. triplets) of the flavor group must be at the electroweak
scale. The most economical way for that is to use SM Higgs boson(s) as flavons.
Such models can be tested by the LHC experiments. This scenario requires the
existence of additional Froggatt-Nielsen scalars that generate hierarchies in
Yukawa couplings. We study the conditions under which large and small flavor
breaking parameters can coexist without destabilizing the dark matter.Comment: 8 pages, no figure
Initial State Radiation in Majorana Dark Matter Annihilations
The cross section for a Majorana Dark Matter particle annihilating into light
fermions is helicity suppressed. We show that, if the Dark Matter is the
neutral Majorana component of a multiplet which is charged under the
electroweak interactions of the Standard Model, the emission of gauge bosons
from the initial state lifts the suppression and allows an s-wave annihilation.
The resulting energy spectra of stable Standard Model particles are importantly
affected. This has an impact on indirect searches for Dark Matter.Comment: 9 pages, 3 figure
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Using Implicit Instructional Cues to Influence False Memory Induction
Previous research has shown that explicit cues specific to the encoding process (endogenous) or characteristic of the stimuli themselves (exogenous) can be used to direct a reader’s attentional resources towards either relational or item-specific information. By directing attention to relational information (and therefore away from item-specific information) the rate of false memory induction can be increased. The purpose of the current study was to investigate if a similar effect would be found by manipulating implicitly endogenous cues. An instructional manipulation was used to influence the perceptual action participants performed on word stimuli during the encoding of DRM list words. Results demonstrated that the instructional conditions that encouraged faster processing also led to an increased rate of false memory induction for semantically related words, supporting the hypothesis that attention was directed towards relational information. This finding supports the impoverished relational processing account of false memory induction. This supports the idea that implicitly endogenous cues, exogenous cues (like font) or explicitly endogenous cues (like training) can direct attentional resources during encoding
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