共查询到20条相似文献,搜索用时 328 毫秒
1.
Gurjav Ganbold 《Physics of Particles and Nuclei》2012,43(1):79-105
We study the behavior of the QCD effective coupling α
s
in the low-energy region by exploiting the conventional meson spectrum within a relativistic quantum-field model based on
analytical confinement of quarks and gluons. The spectra of quark-antiquark and two-gluon bound states are defined by using
a master equation similar to the ladder Bethe-Salpeter equation. A new, independent and specific infrared-finite behavior
of QCD coupling is found below energy scale ∼1 GeV. Particularly, an infrared-fixed point is extracted at α
s
(0) ≅ 0.757 for confinement scale Λ = 345 MeV. We provide a new analytic estimate of the lowest-state glueball mass. As applications,
we also estimate masses of some intermediate and heavy mesons as well as the weak-decay constants of light mesons. By introducing
only a minimal set of parameters (the quark masses m
f
and Λ) we obtain results in reasonable agreement with recent experimental data in a wide range of energy scale ∼0.1–10 GeV.
We demonstrate that global properties of some low-energy phenomena may be explained reasonably in the framework of a simple
relativistic quantum-field model if one guesses correct symmetry structure of the quark-gluon interaction in the confinement
region and uses simple forms of propagators in the hadronisation regime. The model may serve a reasonable framework to describe
simultaneously different sectors in low-energy particle physics. 相似文献
2.
Robert C. Nichol 《General Relativity and Gravitation》2008,40(2-3):249-267
In this review, I outline the use of galaxy correlations to constrain cosmological parameters. As with the cosmic microwave
background (CMB), the density of dark and baryonic matter imprints important scales on the fluctuations of matter and thus
the clustering of galaxies, e.g., the particle horizon at matter-radiation equality and the sound horizon at recombination.
Precision measurements of these scales from the baryon acoustic oscillations (BAO) and the large scale shape of the power
spectrum of galaxy clustering provide constraints on Ω
m
h
2. Recent measurements from the Sloan Digital Sky Survey (SDSS) and 2dF Galaxy Redshift Survey (2dFGRS) strongly suggest that
Ω
m
< 0.3. This forms the basic evidence for a flat Universe dominated by a Cosmological Constant (Λ) today (when combined with
results from the CMB and supernova surveys). Further evidence for this cosmological model is provided by the late-time Integrated
Sachs–Wolfe (ISW) effect, which has now been detected using a variety of tracers of the large scale structure in the Universe
out to redshifts of z > 1. The ISW effect also provides an opportunity to discriminate between Λ, dynamical dark energy models and the modification
of gravity on large scales. 相似文献
3.
D. Atwood S. Bar-Shalom A. Soni 《The European Physical Journal C - Particles and Fields》2006,45(1):219-225
We describe a model for the scalar sector where all interactions occur either at an ultra-high scale, ΛU~1016-1019 GeV, or at an intermediate scale, ΛI = 109-1011 GeV. The interaction of physics on these two scales results in an SU(2) Higgs condensate at the electroweak (EW) scale, ΛEW, through a seesaw-like Higgs mechanism,
, while the breaking of the SM SU(2) x U(1) gauge symmetry occurs at the intermediate scale ΛI . The EW scale is, therefore, not fundamental but is naturally generated in terms of ultra-high energy phenomena and so the
hierarchy problem is alleviated. We show that the class of such "seesaw Higgs" models predict the existence of sub-eV neutrino
masses which are generated through a "two-step" seesaw mechanism in terms of the same two ultra-high scales:
. The neutrinos can be either Dirac or Majorana, depending on the structure of the scalar potential. We also show that our
seesaw Higgs model can be naturally embedded in theories with tiny extra dimensions of size
fm, where the seesaw induced EW scale arises from a violation of a symmetry at a distant brane; in particular, in the scenario
presented there are seven tiny extra dimensions.
Received: 19 August 2004, Revised: 27 July 2005, Published online: 14 October 2005 相似文献
4.
Zhe Chang Ming-Hua Li Xin Li Sai Wang 《The European Physical Journal C - Particles and Fields》2012,72(3):1915
We investigate the possible effect of cosmological-constant type dark energy during the inflation period of the early universe.
This is accommodated by a new dispersion relation in de Sitter space. The modified inflation model of a minimally coupled
scalar field is still able to yield an observation-compatible scale-invariant primordial spectrum, simultaneously having the
potential to generate a spectrum with lower power at large scales. A qualitative match to the WMAP 7-year data is presented.
We obtain an Ω
Λ
of the same order of that in the Λ-CDM model. Possible relations between the de Sitter scenario and Doubly Special Relativity (DSR) are also discussed. 相似文献
5.
We investigate resonances in the pump-probe spectroscopy of Λ configuration of levels in the hyperfine manifold of D
2 transition of 133Cs and a7Rb with specific reference to Autler-Townes splitting, dressed state resonances in double Λ system and electromagnetically induced transparency. As an application, a dark resonance based magnetometer is briefly discussed. 相似文献
6.
T. Padmanabhan 《General Relativity and Gravitation》2008,40(2-3):529-564
I review the problem of dark energy focussing on cosmological constant as the candidate and discuss what it tells us regarding
the nature of gravity. Section 1 briefly overviews the currently popular “concordance cosmology” and summarizes the evidence
for dark energy. It also provides the observational and theoretical arguments in favour of the cosmological constant as a
candidate and emphasizes why no other approach really solves the conceptual problems usually attributed to cosmological constant.
Section 2 describes some of the approaches to understand the nature of the cosmological constant and attempts to extract certain
key ingredients which must be present in any viable solution. In the conventional approach, the equations of motion for matter
fields are invariant under the shift of the matter Lagrangian by a constant while gravity breaks this symmetry. I argue that
until the gravity is made to respect this symmetry, one cannot obtain a satisfactory solution to the cosmological constant
problem. Hence cosmological constant problem essentially has to do with our understanding of the nature of gravity. Section 3 discusses such an alternative perspective on gravity in which the gravitational interaction—described in terms
of a metric on a smooth spacetime—is an emergent, long wavelength phenomenon, and can be described in terms of an effective
theory using an action associated with normalized vectors in the spacetime. This action is explicitly invariant under the
shift of the matter energy momentum tensor T
ab
→ T
ab
+ Λ
gab
and any bulk cosmological constant can be gauged away. Extremizing this action leads to an equation determining the background geometry which gives Einstein’s theory at the lowest order with Lanczos–Lovelock type corrections. In this approach, the observed
value of the cosmological constant has to arise from the energy fluctuations of degrees of freedom located in the boundary
of a spacetime region. 相似文献
7.
We consider non-renormalizable interaction term as perturbation of the conventional neutrino mass matrix. We assume that the
neutrino masses and mixing arise through physics at a scale intermediate between Planck scale and the electroweak breaking
scale. We also assume that, just above the electroweak breaking scale, neutrino masses are nearly degenerate and their mixing
is tetra-maximal. Quantum gravity (Planck scale effects) lead to an effective SU(2)
L
×U(1) invariant dimension-5 Lagrangian involving neutrino and Higgs fields. On electroweak symmetry breaking, this operator
gives rise to correction to the above masses and mixing. These additional term can be consider as a perturbation to the Tetra-maximal
mass matrix. The nature of gravitational interaction demands that the element of this perturbation matrix should be independent
of flavor indices. We compute the deviation of three neutrino mixing angles due to Planck scale effects. We find that there
is no change in θ
13 and θ
23 but change in solar mixing angle θ
12 is suppress by 3.0°. 相似文献
8.
Pawel Horodecki 《Central European Journal of Physics》2003,1(4):695-707
We consider the problem of invariance of distillable entanglement D and quantum capacities Q under erasure of information about single copy of quantum state or channel respectively. We argue that any 2 ⊗N two-way distillable state is still two-way distillable after erasure of single copy information. For some known distillation
protocols the obtained two-way distillation rate is the same as if Alice and Bob knew the state from the very beginning. The
isomorphism between quantum states and quantum channels is also investigated. In particular it is pointed out that any transmission
rate down the channel is equal to distillation rate with formal LOCC-like superoperator that uses in general nonphysical Alice
actions. This allows to we prove that if given channel Λ has nonzero capacity (Q
→ or Q
⟺) then the corresponding quantum state ϱ(Λ) has nonzero distillable entanglement (D
→ or D
⟺). Follwoing the latter arguments are provided that any channel mapping single qubit into N level system allows for reliable two-way transmission after erasure of information about single copy. Some open problems
are discussed. 相似文献
9.
John Ellis Azar Mustafayev Keith A. Olive 《The European Physical Journal C - Particles and Fields》2011,71(7):1689
We explore the phenomenology of the minimal supersymmetric flipped SU(5) GUT model (CFSU(5)), whose soft supersymmetry-breaking
(SSB) mass parameters are constrained to be universal at some input scale, M
in
, above the GUT scale, M
GUT. We analyze the parameter space of CFSU(5) assuming that the lightest supersymmetric particle (LSP) provides the cosmological
cold dark matter, paying careful attention to the matching of parameters at the GUT scale. We first display some specific
examples of the evolutions of the SSB parameters that exhibit some generic features. Specifically, we note that the relationship
between the masses of the lightest neutralino χ and the lighter stau [(t)\tilde]1{\tilde{\tau}_{1}} is sensitive to M
in
, as is the relationship between m
χ
and the masses of the heavier Higgs bosons A,H. For these reasons, prominent features in generic (m
1/2,m
0) planes such as coannihilation strips and rapid-annihilation funnels are also sensitive to M
in
, as we illustrate for several cases with tan β=10 and 55. However, these features do not necessarily disappear at large M
in
, unlike the case in the minimal conventional SU(5) GUT. Our results are relatively insensitive to neutrino masses. 相似文献
10.
The possible existence of higher multi-quark flavor multiplets of baryons is investigated. We argue that the S-matrix should have poles with any quantum numbers, including those which are exotic. This argument provides a novel justification
for the existence of hadrons with arbitrary exotic structure. Though it does not constitute a proof, there are still no theoretical
arguments against exotics. We then consider KN and πN scattering. Conventional and modified partial-wave analyses provide several sets of candidates for correlated pairs (Θ1,Δ), each of which could label a related 27-plet. Properties of the pairs (masses, mass orderings, spin-parity quantum numbers) do not quite correspond to the current
theoretical expectations. Decay widths of the candidates are either wider or narrower than expected. Possible reasons for
such disagreements are briefly discussed. 相似文献
11.
Bipin Singh Koranga 《International Journal of Theoretical Physics》2011,50(1):42-47
We consider non renormalization 1/M
x
interaction term as a perturbation of the neutrino mass matrix. We find that for the degenerate neutrino mass spectrum. We
assume that the neutrino masses and mixing arise through physics at a scale intermediate between Planck Scale and the electroweak
scale. We also assume, above the electroweak breaking scale, neutrino masses are nearly degenerate and their mixing is bimaximal.
The perturbation generates a non zero value of θ
13, which is within reach of the high performance neutrino factory. In this paper, we find that the non zero value of θ
13 due to Planck scale effects indicates the possibility of CP violation. 相似文献
12.
V. Fayaz H. Hossienkhani F. Felegary 《International Journal of Theoretical Physics》2012,51(8):2656-2664
We have investigated general Bianchi type I cosmological models which containing a perfect fluid and dark energy with time varying G and Λ that have been presented. The perfect fluid is taken to be one obeying the equation of state parameter, i.e., p=ωρ; whereas the dark energy density is considered to be either modified polytropic or the Chaplygin gas. Cosmological models admitting both power-law which is explored in the presence of perfect fluid and dark energy too. We reconstruct gravitational parameter G, cosmological term Λ, critical density ρ c , density parameter Ω, cosmological constant density parameter Ω Λ and deceleration parameter q for different equation of state. The present study will examine non-linear EOS with a general nonlinear term in the energy density. 相似文献
13.
We consider the astrophysical and cosmological implications of the existence of a minimum density and mass due to the presence
of the cosmological constant. If there is a minimum length in nature, then there is an absolute minimum mass corresponding
to a hypothetical particle with radius of the order of the Planck length. On the other hand, quantum mechanical considerations
suggest a different minimum mass. These particles associated with the dark energy can be interpreted as the “quanta” of the
cosmological constant. We study the possibility that these particles can form stable stellar-type configurations through gravitational
condensation, and their Jeans and Chandrasekhar masses are estimated. From the requirement of the energetic stability of the
minimum density configuration on a macroscopic scale one obtains a mass of the order of 1055 g, of the same order of magnitude as the mass of the universe. This mass can also be interpreted as the Jeans mass of the
dark energy fluid. Furthermore we present a representation of the cosmological constant and of the total mass of the universe
in terms of ‘classical’ fundamental constants. 相似文献
14.
15.
We show that the temperature-generalization of a popular model of quark-confinement seems to provide a rather interesting
insight into the origin of mass of elementary particles: as the universe cooled, there was an era when particles did not have
an identity since their masses were variable; the temperature at which the conversion of these ‘nomadic’ particles into ‘elementary’
particles took place seems to have been governed by the value of a dimension-less coupling constantC
c. ForC
c=0.001(0.1) this temperature is of the order of 109 K (1011 K), below which the particle masses do not change. 相似文献
16.
A new dark energy model called “ghost dark energy” was recently suggested to explain the observed accelerating expansion of
the universe. This model originates from the Veneziano ghost of QCD. The dark energy density is proportional to Hubble parameter,
ρ
D
= α H, where α is a constant of order LQCD3{\Lambda_{\rm QCD}^3} and ΛQCD ~ 100 MeV is QCD mass scale. In this Letter, we extend the ghost dark energy model to the universe with spatial curvature
in the presence of interaction between dark matter and dark energy. We study cosmological implications of this model in detail.
In the absence of interaction the equation of state parameter of ghost dark energy is always w
D
> −1 and mimics a cosmological constant in the late time, while it is possible to have w
D
< −1 provided the interaction is taken into account. When k = 0, all previous results of ghost dark energy in flat universe are recovered. For the observational test, we use Supernova
type Ia Gold sample, shift parameter of cosmic microwave background radiation and the correlation of acoustic oscillation
on the last scattering surface and the baryonic acoustic peak from Sloan Digital Sky Survey are used to confine the value
of free parameter of mentioned model. 相似文献
17.
Utpal Mukhopadhyay Saibal Ray A. A. Usmani Partha Pratim Ghosh 《International Journal of Theoretical Physics》2011,50(3):752-759
We perform a deductive study of accelerating Universe and focus on the importance of variable time-dependent Λ in the Einstein’s
field equations under the phenomenological assumption, Λ=αH
2 for the full physical range of α. The relevance of variable Λ with regard to various key issues like dark matter, dark energy, geometry of the field, age
of the Universe, deceleration parameter and barotropic equation of state has been trivially addressed. The deceleration parameter
and the barotropic equation of state parameter obey a straight line relationship for a flat Universe described by Friedmann
and Raychaudhuri equations. Both the parameters are found identical for α=1. 相似文献
18.
M. Malekjani A. Khodam-Mohammadi M. Taji 《International Journal of Theoretical Physics》2011,50(10):3112-3124
The polytropic gas model is investigated as an interacting dark energy scenario. The cosmological implications of the model
including the evolution of EoS parameter w
Λ, energy density ΩΛ and deceleration parameter q are investigated. We show that, depending on the parameter of model, the interacting polytropic gas can behave as a quintessence
or phantom dark energy. In this model, the phantom divide is crossed from below to up. The evolution of q in the context of polytropic gas dark energy model represents the decelerated phase at the early time and accelerated phase
later. The singularity of this model is also discussed. Eventually, we establish the correspondence between interacting polytropic
gas model with tachyon, K-essence and dilaton scalar fields. The potential and the dynamics of these scalar field models are
reconstructed according to the evolution of interacting polytropic gas. 相似文献
19.
Alain Bachelot 《Communications in Mathematical Physics》2008,283(1):127-167
We investigate the global solutions of the Dirac equation on the Anti- de-Sitter Universe. Since this space is not globally
hyperbolic, the Cauchy problem is not, a priori, well-posed. Nevertheless we can prove that there exists unitary dynamics, but its uniqueness crucially depends on the ratio
beween the mass M of the field and the cosmological constant Λ > 0: it appears a critical value, Λ/12, which plays a role similar to the Breitenlohner-Freedman
bound for the scalar fields. When M
2 ≥ Λ/12 there exists a unique unitary dynamics. On the contrary, for the light fermions satisfying M
2 < Λ/12, we construct several asymptotic conditions at infinity, such that the problem becomes well-posed. In all the cases,
the spectrum of the hamiltonian is discrete. We also prove a result of equipartition of the energy. 相似文献
20.
A. Valcarce H. Garcilazo J. Vijande 《The European Physical Journal A - Hadrons and Nuclei》2008,37(2):217-225
The recent observation at CDF and D0 of Σ
b
, Σ
b
* and Ξ
b
baryons opens the door to the advent of new states in the bottom baryon sector. The states measured provide sufficient constraints
to fix the parameters of phenomenological models. One may therefore consistently predict the full bottom baryon spectra. For
this purpose we have solved exactly the three-quark problem by means of the Faddeev method in momentum space. We consider
our guidance may help experimentalists in the search for new bottom baryons and their findings will help in constraining further
the phenomenological models. We identify particular states whose masses may allow to discriminate between the dynamics for
the light quark pairs predicted by different phenomenological models. Within the same framework we also present results for
charmed, doubly charmed, and doubly bottom baryons. Our results provide a restricted possible assignment of quantum numbers
to recently reported charmed-baryon states. Some of them are perfectly described by D-wave excitations with J
P
= 5/2+, as the Λ
c
(2880), Λ
c
(3055), and Λ
c
(3123).
Communicated by V. Vento 相似文献