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Search Results: 1 - 10 of 401458 matches for " M. Shaposhnikov "
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On Non-Perturbative Effects at the High-Temperature Electroweak Phase Transition
M. Shaposhnikov
Physics , 1993, DOI: 10.1016/0370-2693(93)90666-6
Abstract: It is argued that confining effects in 3-dimensional non-Abelian gauge theories (high-temperature limit of 4-dimensional ones) imply the existence of the condensates of the gauge and Higgs fields in 3-d vacuum. This non-perturbative effect can decrease the energy of the phase with unbroken symmetry and may result in the creation of a barrier separating the broken and unbroken phases. Thus the high-temperature phase transitions in gauge theories can be stronger first order than is expected from perturbation theory. The applications of these results to electroweak baryogenesis are briefly discussed.
Thermodynamics of Non-Topological Solitons
M. Laine,M. Shaposhnikov
Physics , 1998, DOI: 10.1016/S0550-3213(98)00474-X
Abstract: In theories with low energy supersymmetry breaking, the effective potential for squarks and sleptons has generically nearly flat directions, V(phi) ~ M^4 (log(phi/M))^n. This guarantees the existence of stable non-topological solitons, Q-balls, that carry large baryon number, B >> (M/m_p)^4, where m_p is the proton mass. We study the behaviour of these objects in a high temperature plasma. We show that in an infinitely extended system with a finite density of the baryon charge, the equilibrium state is not homogeneous and contains Q-balls at any temperature. In a system with a finite volume, Q-balls evaporate at a volume dependent temperature. In the cosmological context, we formulate the conditions under which Q-balls, produced in the Early Universe, survive till the present time. Finally, we estimate the baryon to cold dark matter ratio in a cosmological scenario in which Q-balls are responsible for both the net baryon number of the Universe and its dark matter. We find out naturally the correct orders of magnitude for M ~ 1...10 TeV: \eta ~ 10^{-10} (M/TeV)^{-2} (B/10^{26})^{-1/2}.
Primordial Magnetic Fields, Right Electrons, and the Abelian Anomaly
M. Joyce,M. Shaposhnikov
Physics , 1997, DOI: 10.1103/PhysRevLett.79.1193
Abstract: In the standard model there are charges with abelian anomaly only (e.g. right-handed electron number) which are effectively conserved in the early universe until some time shortly before the electroweak scale. A state at finite chemical potential of such a charge, possibly arising due to asymmetries produced at the GUT scale, is unstable to the generation of hypercharge magnetic field. Quite large magnetic fields ($\sim 10^{22}$ gauss at $T\sim 100$ GeV with typical inhomogeneity scale $ \sim \frac{ 10^6}{T}$) can be generated. These fields may be of cosmological interest, potentially acting as seeds for amplification to larger scale magnetic fields through non-linear mechanisms. Previously derived bounds on exotic $B-L$ violating operators may also be evaded.
Primordial magnetic fields from inflation?
M. Giovannini,M. Shaposhnikov
Physics , 2000, DOI: 10.1103/PhysRevD.62.103512
Abstract: The hot plasma above the electroweak scale contains (hyper) charged scalar particles which are coupled to Abelian gauge fields. Scalars may interact with gravity in a non-conformally invariant way and thus their fluctuations can be amplified during inflation. These fluctuations lead to creation of electric currents and produce inhomogeneous distribution of charge density, resulting in the generation of cosmological magnetic fields. We address the question whether these fields can be coherent at large scales so that they may seed the galactic magnetic fields. Depending upon the mass of the charged scalar and upon various cosmological (critical fraction of energy density in matter, Hubble constant) and particle physics parameters we found that the magnetic fields generated in this way are much larger than vacuum fluctuations. However, their amplitude on cosmological distances is found to be too small for seeding the galactic magnetic fields.
An all-order discontinuity at the electroweak phase transition
M. Laine,M. Shaposhnikov
Physics , 1999, DOI: 10.1016/S0370-2693(99)01014-X
Abstract: We define a non-local gauge-invariant Green's function which can distinguish between the symmetric (confinement) and broken (Higgs) phases of the hot SU(2)xU(1) electroweak theory to all orders in the perturbative expansion. It is related to the coupling of the Chern-Simons number to a massless Abelian gauge field. The result implies either that there is a way to distinguish between the phases, even though the macroscopic thermodynamical properties of the system have been observed to be smoothly connected, or that the perturbative Coleman-Hill theorem on which the argument is based, is circumvented by non-perturbative effects. We point out that this question could in principle be studied with three-dimensional lattice simulations.
A remark on sphaleron erasure of baryon asymmetry
M. Laine,M. Shaposhnikov
Physics , 1999, DOI: 10.1103/PhysRevD.61.117302
Abstract: We complete an existing result for how the baryon asymmetry left over after a period of full thermal equilibrium depends on different lepton asymmetries.
Chiral Asymmetry from a 5D Higgs Mechanism
Salvio, A.;Shaposhnikov, M.
High Energy Physics - Phenomenology , 2007, DOI: 10.1088/1126-6708/2007/11/037
Abstract: An intriguing feature of the Standard Model is that the representations of the unbroken gauge symmetries are vector-like whereas those of the spontaneously broken gauge symmetries are chiral. Here we provide a toy model which shows that a natural explanation of this property could emerge in higher dimensional field theories and discuss the difficulties that arise in the attempt to construct a realistic theory. An interesting aspect of this type of models is that the 4D low energy effective theory is not generically gauge invariant. However, the non-invariant contributions to the observable quantities are very small, of the order of the square of the ratio between the light particle mass scale and the Kaluza-Klein mass scale. Remarkably, when we take the unbroken limit both the chiral asymmetry and the non-invariant terms disappear.
Strong Sphalerons and Electroweak Baryogenesis
G. Giudice,M. Shaposhnikov
Physics , 1993, DOI: 10.1016/0370-2693(94)91202-5
Abstract: We analyze the spontaneous baryogenesis and charge transport mechanisms suggested by Cohen, Kaplan and Nelson for baryon asymmetry generation in extended versions of electroweak theory. We find that accounting for non-perturbative chirality-breaking transitions due to strong sphalerons reduces the baryonic asymmetry by the factor $(m_t/\pi T)^2$ or $\alpha_W$, provided those processes are in thermal equilibrium.
Finite temperature effective theories
M. E. Shaposhnikov
Physics , 1996,
Abstract: Lecture Notes, Summer School on Effective Theories and Fundamental Interactions, Erice, July 1996. I describe the construction of effective field theories for equilibrium high-temperature plasma of elementary particles.
Standard Model Higgs boson mass from inflation: two loop analysis
F. Bezrukov,M. Shaposhnikov
Physics , 2009, DOI: 10.1088/1126-6708/2009/07/089
Abstract: We extend the analysis of \cite{Bezrukov:2008ej} of the Standard Model Higgs inflation accounting for two-loop radiative corrections to the effective potential. As was expected, higher loop effects result in some modification of the interval for allowed Higgs masses m_min
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