255,959 research outputs found
Probing Confinement with Chromomagnetic Fields
Using the lattice Schr\"odinger functional we study vacuum dynamics of SU(3)
gauge theory at finite temperature. The vacuum is probed by means of an
external constant Abelian chromomagnetic field. We find that by increasing the
strength of the applied external field the deconfinement temperature decreases
towards zero. This implies that strong enough Abelian chromomagnetic fields
destroy confinement of color.Comment: Lattice2002(topology). 3 pages, 3 figure
Exploring the Dynamics of Three-Dimensional Lattice Gauge Theories by External Fields
We investigate the dynamics of three-dimensional lattice gauge theories by
means of an external Abelian magnetic field. For the SU(2) lattice gauge theory
we find evidence of the unstable modes.Comment: 3 pages, PostScript. Contribution to the LATTICE 93 Conference
(Dallas, U.S.A., September 1993) preprint BARI-TH-162/9
Investigations on the deconfining phase transition in QCD
We investigate the deconfining phase transition in SU(3) pure gauge theory
and in full QCD with two flavors of staggered fermions by means of a gauge
invariant thermal partition functional. In the pure gauge case our finite size
scaling analysis is in agreement with the well known weak first order phase
transition. In the case of 2 flavors full QCD we find that the phase transition
is consistent with weak first order, contrary to the expectation of a crossover
for not too large quark masses.Comment: 3 pages, 3 figures, Lattice2003(topology
Unstable Modes and Confinement in the Lattice Schr\"odinger Functional Approach
We analyze the problem of the Nielsen-Olesen unstable modes in the SU(2)
lattice gauge theory by means of a recently introduced gauge-invariant
effective action. We perform numerical simulations in the case of a constant
Abelian chromomagnetic field. We find that for lattice sizes above a certain
critical length the density of effective action shows a behaviour compatible
with the presence of the unstable modes. We put out a possible relation between
the dynamics of the unstable modes and the confinement.Comment: 15 pages, LaTeX2e file, 5 figure
No Primordial Magnetic Field from Domain Walls
It is pointed out that, contrary to some claims in the literature, the domain
walls cannot be a source of a correlated at large scales primordial magnetic
field, even if the fermionic modes bound on the wall had ferromagnetic
properties. In a particular model with massive (2+1) dimensional fermions bound
to a domain wall, previously claimed to exhibit a ferromagnetic behavior, it is
explicitly shown that the fermionic system in fact has properties of a normal
diamagnetic with the susceptibility vanishing at high temperature.Comment: 8 pages. Modified discussion of the baryon density on an axion domain
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Indications on the Higgs boson mass from lattice simulations
The `triviality' of has been traditionally interpreted within
perturbation theory where the prediction for the Higgs boson mass depends on
the magnitude of the ultraviolet cutoff . This approach crucially
assumes that the vacuum field and its quantum fluctuations rescale in the same
way. The results of the present lattice simulation, confirming previous
numerical indications, show that this assumption is not true. As a consequence,
large values of the Higgs mass can coexist with the limit . As an example, by extrapolating to the Standard Model our results
obtained in the Ising limit of the one-component theory, one can obtain a value
as large as GeV, independently of .Comment: 3 pages, 2 figures, Lattice2003(higgs
Identification of a Carcinoembryonic Antigen Gene Family in the Rat
The existence of a carcinoembryonic antigen (CEA)-like gene family in rat has been demonstrated through isolation and sequencing of the N- terminal domain exons of presumably five discrete genes (rnCGM1-5). This finding will allow for the first time the study of functional and clinical aspects of the tumor marker CEA and related antigens in an animal model. Sequence comparison with the corresponding regions of members of the human CEA gene family revealed a relatively low similarity at the amino acid level, which indicates rapid divergence of the CEA gene family during evolution and explains the lack of cross- reactivity of rat CEA-like antigens with antibodies directed against human CEA. The N-terminal domains of the rat CEA-like proteins show structural similarity to immunoglobulin variable domains, including the presence of hypervariable regions, which points to a possible receptor function of the CEA family members. Although so far only one of the five rat CEA-like genes could be shown to be transcriptionally active, multiple mRNA species derived from other members of the rat CEA-like gene family have been found to be differentially expressed in rat placenta and liver
Long-wavelength excitations of Higgs condensates
Quite independently of the Goldstone phenomenon, recent lattice data suggest
the existence of gap-less modes in the spontaneously broken phase of a theory. This result is a direct consequence of the quantum nature of
the `Higgs condensate' that cannot be treated as a purely classical c-number
field.Comment: 6 page
Dynamical Generation of the Primordial Magnetic Field by Ferromagnetic Domain Walls
The spontaneous generation of uniform magnetic condensate in gives
rise to ferromagnetic domain walls at the electroweak phase transition. These
ferromagnetic domain walls are caracterized by vanishing effective surface
energy density avoiding, thus, the domain wall problem. Moreover we find that
the domain walls generate a magnetic field at the
electroweak scale which account for the seed field in the so called dynamo
mechanism for the cosmological primordial magnetic field. We find that the
annihilation processes of walls with size could release an
energy of order indicating the invisible ferromagnetic walls as
possible compact sources of Gamma Ray Bursts.Comment: LaTeX, 8 pages, 1 figur
Analysis of the Size of the Carcinoembryonic Antigen (CEA) Gene Family
Five members of the human CEA gene family [human pregnancy-specific ÎČ1-glycoprotein (PSÎČG), hsCGM1, 2, 3 and 4] have been isolated and identified through sequencing the exons containing their N-terminal domains. Sequence comparisons with published data for CEA and related molecules reveal the existence of highly-conserved gene subgroups within the CEA family. Together with published data eleven CEA family members have so far been determined. Apart from the highly conserved coding sequences, these genes also show strong sequence conservation in their introns, indicating a duplication of whole gene units during the evolution of the CEA gene family
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