arXiv subjects

E. I. Guendelman

Publications and source records attributed to E. I. Guendelman.

At least 73 records · Page 4Linked to original sources

arXiv2004

Cosmic Coincidence with a new Type of Dark Matter

A field theory is proposed where the regular fermionic matter and the dark fermionic matter are different states of the same "primordial" fermion fields. In regime of the fermion densities typical for normal particle physics, the primordial fermions split into three families identified with regular fermions. When fermion energy density becomes comparable with dark energy density, the theory allows new type of states. The possibility of such Cosmo-Low Energy Physics (CLEP) states is demonstrated by means of solutions of the field theory equations describing FRW universe filled by homogeneous scalar field and uniformly distributed nonrelativistic neutrinos. Neutrinos in CLEP state are drawn into cosmological expansion by means of dynamically changing their own parameters. One of the features of the fermions in CLEP state is that in the late time universe their masses increase as a^{3/2} (a=a(t) is the scale factor). The energy density of the cold dark matter consisting of neutrinos in CLEP state scales as a sort of dark energy; this cold dark matter possesses negative pressure and for the late time universe its equation of state approaches that of the cosmological constant. The total energy density of such universe is less than it would be in the universe free of fermionic matter at all. The (quintessence) scalar field is coupled to dark matter but its coupling to regular fermionic matter appears to be extremely strongly suppressed.

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arXiv2004

Some Cosmological Applications of Two Measures Theory

Scale invariance is considered in the context of a gravitational theory where the action, in the first order formalism, is of the form S = \int L_{1} Φd^4x + \int L_{2}\sqrt{-g}d^4x where Φis a density built out of degrees of freedom independent of the metric. For global scale invariance, a "dilaton" ϕhas to be introduced, with non-trivial potentials V(ϕ)=f_{1}e^{αϕ} in L_1 and U(ϕ) = f_{2}e^{2αϕ} in L_2. In the effective Einstein frame, this leads to a non-trivial ϕpotential (of the Morse type) which has a flat region with energy density f_{1}^{2}/4f_{2} as ϕ\to\infty. The addition of an R^{2} term produces an effective potential with two connected flat regions: one of the Planck scale, that can be responsible for early inflation, and another for the description of the present universe.

gr-qc↗

arXiv2004

Conformally Invariant Brane-universe and the Cosmological Constant

A relativistic 3-brane can be given a conformally invariant, gauge-type, formulation provided the embedding space is six-dimensional. The implementation of conformal invariance requires the use of a modified measure, independent of the metric in the action. A brane-world scenario without the need of a cosmological constant in 6D can be constructed. Thus, no ``old'' cosmological constant problem appears at this level.

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arXiv2004

Coulomb interaction from the interplay between Confinement and Screening

It has been noticed that confinement effects can be described by the addition of a $ \sqrt {- F_{μν}^a F^{aμν}} $ term in the Lagrangian density. We now study the combined effect of such "confinement term" and that of a mass term. The surprising result is that the interplay between these two terms gives rise to a Coulomb interaction. Our picture has a certain correspondence with the quasiconfinement picture described by Giles, Jaffe and de Rujula for QCD with symmetry breaking.

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arXiv2004

Impact of Dynamical Tensions in Modified String and Brane Theories

First we briefly outline the general construction of Dp-brane models with dynamical tensions. We then proceed to a more detailed discussion of a modified string model where the string tension is related to the potential of (an external) world-sheet electric current. We show that cancellation of the pertinent conformal anomaly on the quantum level requires the dynamical string tension to be a square of a free massless world-sheet scalar field.

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arXiv2003

Geometrical Origin of Fermion Families in SU(2)xU(1) Gauge Theory

A spontaneously broken SU(2)xU(1) gauge theory with just one "primordial" generation of fermions is formulated in the context of generally covariant theory which contains two measures of integration in the action: the standard \sqrt{-g}d^{4}x and a new Φd^{4}x, where Φis a density built out of degrees of freedom independent of the metric. Such type of models are known to produce a satisfactory answer to the cosmological constant problem. Global scale invariance is implemented. After SSB of scale invariance and gauge symmetry it is found that with the conditions appropriate to laboratory particle physics experiments, to each primordial fermion field corresponds three physical fermionic states. Two of them correspond to particles with constant masses and they are identified with the first two generations of the electro-weak theory. The third fermionic states at the classical level get non-polynomial interactions which indicate the existence of fermionic condensate and fermionic mass generation.

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arXiv2003

SSB of scale symmetry, fermion families and quintessence without the long-range force problem

We study a scale invariant two measures theory where a dilaton field ϕhas no explicit potentials. The scale transformations include a shift ϕ\toϕ+const. The theory demonstrates a new mechanism for gene- ration of the exponential potential: in the conformal Einstein frame (CEF), after SSB of scale invariance, the theory develops the exponential potential and, in general, non-linear kinetic term is generated as well. The possibility of quintessence solutions are shown. As an example, for one choice of the parameters we obtain standard scaling solutions usually used in the context of the quintessential scenario. For other choice of the parameters, the theory allows a scaling solution with equation of state p_ϕ=wρ_ϕ where w is restricted by -1<w<-0.82. The regime where the fermionic matter dominates (as compared to the dilatonic contribution) is analyzed. There it is found that starting from a single fermionic field we obtain exactly three different types of spin 1/2 particles in CEF that appears to suggest a new approach to the family problem of particle physics. It is automatically achieved that for two of them, fermion masses are constants, gravitational equations are canonical and the "fifth force" is absent. For the third type of particles, a fermionic self-interaction appears as a result of SSB of scale invariance.

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arXiv2003

The Cornell confining potential from spontaneous breaking of scale symmetry

We show that one can obtain naturally the Cornell confining potential from the spontaneous symmetry breaking of scale invariance in gauge theory. At the classical level a confining force is obtained and at the quantum level, using a gauge invariant but path-dependent variables formalism, the Cornell confining potential is explicitly obtained.

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arXiv2003

Gauged Dimension Bubbles

Some of the peculiar electrodynamical effects associated with gauged ``dimension bubbles'' are presented. Such bubbles, which effectively enclose a region of 5d spacetime, can arise from a 5d theory with a compact extra dimension. Bubbles with thin domain walls can be stabilized against total collapse by the entrapment of light charged scalar bosons inside the bubble, extending the idea of a neutral dimension bubble to accommodate the case of a gauged U(1) symmetry. Using a dielectric approach to the 4d dilaton-Maxwell theory, it is seen that the bubble wall is almost totally opaque to photons, leading to a new stabilization mechanism due to trapped photons. Photon dominated bubbles very slowly shrink, resulting in a temperature increase inside the bubble. At some critical temperature, however, these bubbles explode, with a release of radiation.

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arXiv2003

Scale Symmetry Breaking from the Dynamics of Maximal Rank Gauge Field Strengths

Scale invariant theories which contain maximal rank gauge field strengths (of $D$ indices in $D$ dimensions) are studied. The integration of the equations of motion of these gauge fields leads to the s.s.b. of scale invariance. The cases in study are: i) the spontaneous generation of $r^{-1}$ potentials in particle mechanics in a theory that contains only $r^{-2}$ potentials in the scale invariant phase, ii) mass generation in scalar field theories iii) generation of non trivial dilaton potentials in generally covariant theories, iv) spontaneous generation of confining behavior in gauge theories. The possible origin of these models is discussed.

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arXiv2003

Conformally Invariant Braneworld and the Cosmological Constant

A six dimensional braneworld scenario based on a model describing the interaction of gravity, gauge fields and 3+1 branes in a conformally invariant way is described. The action of the model is defined using a measure of integration built of degrees of freedom independent of the metric. There is no need to fine tune any bulk cosmological constant or the tension of the two (in the scenario described here) parallel branes to obtain zero cosmological constant, the only solutions are those with zero 4-D cosmological constant. The two extra dimensions are compactified in a "football" fashion and the branes lie on the two opposite poles of the compact "football-shaped" sphere.

gr-qc↗

arXiv2003

Counter-example where cosmic time keeps its original role in quantum cosmology

In the minisuperspace models of quantum cosmology, the absence of time in the Wheeler-DeWitt (constraint) equation, is the main point leading to the generally accepted conclusion that in the quantum cosmology there is no possibility to describe the evolution of the universe procceding in the cosmic time (the time usually used in classical cosmology). We show that in spite of the constraint, under the specific circumstances, the averaging of some of the Heisenberg equations can give nontrivial additional information about explicit time dependence of the expectation values of certain dynamical variables in quantum cosmology. This idea is realized explicitly in a higher dimensional model with a negative cosmological constant and dust as the sources of gravity. When there is an anisotropy in the evolution of the universe, the above phenomenon (i.e. explicit cosmic time dependence of certain expectation values) appears and we find the new quantum effect which consists in "quantum inflationary phase" for some dimensions and simultaneous "quantum deflationary contraction" for the remaining dimensions. The expectation value of the "volume" of the universe remains constant during this quantum "inflation-deflation" process.

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arXiv2002

Inflation and Transition to a Slowly Accelerating Phase from S.S.B. of Scale Invariance

We consider the effects of adding a scale invariant $R^{2}$ term to the action of the scale invariant model (SIM) studied previously by one of us (E.I.G., Mod. Phys. Lett. A14, 1043 (1999)). The SIM belongs to the general class of theories, where an integration measure independent of the metric is introduced. To implement scale invariance (S.I.), a dilaton field is introduced. The integration of the equations of motion associated with the new measure gives rise to the spontaneous symmetry breaking (S.S.B) of S.I.. After S.S.B. of S.I. in the model with the $R^{2}$ term, it is found that a non trivial potential for the dilaton is generated. This potential contains two flat regions: one associated with the Planck scale and with an inflationary phase, while the other flat region is associated to a very small vacuum energy (V.E.) and is associated to the present slowly accelerated phase of the universe (S.A.PH). The smallness of the V.E. in the S.A.PH. is understood through the see saw mechanism introduced in S.I.M.

gr-qc↗

arXiv2002

Nambu-Goto Strings from SU(N) Born-Infeld model

The spectrum of quenched Yang-Mills theory in the large-N limit displays strings and higher dimensional extended objects. The effective dynamics of string-like excitations is encoded into area preserving Schild action. In this letter, we bridge the gap between SU(N) gauge models and fully reparametrization invariant Nambu-Goto string models by introducing an extra matrix degree of freedom in the Yang-Mills action. In the large-N limit this matrix variable becomes the world-sheet auxiliary field allowing a smooth transition between the Schild and Nambu-Goto strings. The new improved matrix model we propose here can be extended to p-branes provided we enlarge the dimensionality of the target spacetime.

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arXiv2001

Interactions from SSB of scale symmetry: applications to problems of quintessence, galaxy dark matter and fermion family

We study a scale invariant two measures theory where a dilaton field ϕhas no explicit potentials. The scale transformations include a shift ϕ\toϕ+const. The theory demonstrates a new mechanism for generation of the exponential potential: in the conformal Einstein frame (CEF), after SSB of scale invariance, the theory develops the exponential potential and, in general, non-linear kinetic term is generated as well. The possibility of quintessence and of halo dark matter solutions are shown. The regime where the fermionic matter dominates (as compared to the dilatonic contribution) is analyzed. There it is found that starting from a single fermionic field we obtain exactly three different types of spin 1/2 particles in CEF that appears to suggest a new approach to the family problem of particle physics. It is automatically achieved that for two of them, fermion masses are constants, gravitational equations are canonical and the "fifth force" is absent. For the third type of particles, four fermionic interaction appears from SSB of scale invariance.

hep-th↗

arXiv2001

A New Measure, Scale Invariance and See Saw Cosmology

The cosmological constant problem and the possibility of obtaining a see saw cosmological effect, where the effective vacuum energy is highly suppressed by the existence of a large scale is investigated in the context of scale-invariant, generally covariant theory. Scale invariance is considered in the context of a gravitational theory where the action, in the first order formalism, is of the form $S = \int L_{1} Φd^4x$ + $\int L_{2}\sqrt{-g}d^4x$ where $Φ$ is a density built out of degrees of freedom independent of the metric.

hep-th↗

arXiv2001

Scale Invariance and Vacuum Energy

The possibility of mass in the context of scale-invariant, generally covariant theories, is discussed. Scale invariance is considered in the context of a gravitational theory where the action, in the first order formalism, is of the form $S = \int L_{1} Φd^4x$ + $\int L_{2}\sqrt{-g}d^4x$ where $Φ$ is a density built out of degrees of freedom independent of the metric. For global scale invariance, a "dilaton" $ϕ$ has to be introduced, with non-trivial potentials $V(ϕ)$ = $f_{1}e^{αϕ}$ in $L_1$ and $U(ϕ)$ = $f_{2}e^{2αϕ}$ in $L_2$. This leads to non-trivial mass generation and a potential for $ϕ$ which is interesting for new inflation. Scale invariant mass terms for fermions lead to a possible explanation of the present day accelerated universe and of cosmic coincidences.

hep-th↗

arXiv2000

The volume element of space-time and scale invariance

Scale invariance is considered in the context of gravitational theories where the action, in the first order formalism, is of the form $S = \int L_{1} Φd^4x$ + $\int L_{2}\sqrt{-g}d^4x$ where the volume element $Φd^4x$ is independent of the metric. For global scale invariance, a "dilaton" $ϕ$ has to be introduced, with non-trivial potentials $V(ϕ)$ = $f_{1}e^{αϕ}$ in $L_1$ and $U(ϕ)$ = $f_{2}e^{2αϕ}$ in $L_2$. This leads to non-trivial mass generation and a potential for $ϕ$ which is interesting for inflation. Interpolating models for natural transition from inflation to a slowly accelerated universe at late times appear naturally. This is also achieved for "Quintessential models", which are scale invariant but formulated with the use of volume element $Φd^4x$ alone. For closed strings and branes (including the supersymmetric cases), the modified measure formulation is possible and does not require the introduction of a particular scale (the string or brane tension) from the begining but rather these appear as integration constants.

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