UNIFIED FIELD — THE UNIVERSAL BLUEPRINT ?

The current status of the studies of the origin of the fundamental particles and the universe is presented. These studies indicate the unified field to be the source of both the fundamental particles and the universe itself. Furthermore, as a consequence of the unique properties of the quantum vacuum, the unified field is presumed to exist, in a quantum physical sense, everywhere in the very fabric of spacetime. In an analogy to the characteristics of the human genome, unified field appears to have the basic blueprint of at least everything physical in this universe.


INTRODUCTION
As the twentieth century comes to a close and a new millennium begins, human beings can be truly proud of having achieved some extraordinary scientiÞc breakthroughs in this century. The early twentieth century started with two revolutionary theories: relativity and quantum mechanics, which dramatically changed our view of the world. Applying special theory of relativity to quantum mechanics gave rise to the quantum Þeld theories that eventually led to the development of the uniÞed Þeld theories.
Among the numerous, exciting scientiÞc achievements of our century, perhaps the most outstanding is the advent of the unif ied f ield. Both the search for the origin of the fundamental particles and that of our universe point to the uniÞed Þeld as the ultimate source. Thus, for the Þrst time, we are given an objective glimpse of how our universe, and we, came to exist.
This profound knowledge at its present state of development is more like an impressionistic painting where the scenery is discernible while all the details are not. But enough elements of the detail have emerged to give us some conÞdence in the validity of the scenario. However, either the superstring theory or a successful theory of quantum gravity promises to reveal further details sometime early next century.
According to modern cosmology, the distinguishable part of this picture appears to be that the spontaneous symmetry breaking of the uniÞed Þeld started our universe from the incredibly small, Planck's dimension of 10 −33 cm. The uniÞed Þeld, containing the blueprint of the entire universe, has sequentially unfolded to create everything physical in our universe. After having created the universe, the uniÞed Þeldl is also present now in a quantum physical way, everywhere, in the very fabric of spacetime, thereby upholding and administering our universe and, at least, everything physical it contains. This is quite similar to a reality with which we are more familiar: our genome (DNA), consisting of twenty-three pairs of chromosomes, which is present in the very Þrst cell, possesses the blueprint of an entire human body. After creating the body, it is also present in each cell of the body, controlling different aspects of our bodily functions. Only a small percentage of the DNA is active in an adult cell, and this percentage of expression allows the proper functioning of that particular cell. Nevertheless, the DNA of each cell possesses the entire blueprint of the whole body. This was vividly demonstrated by Ian Wilmut and his colleagues when they created the famous ewe, Dolly, using the DNA from an udder cell of an adult ewe.

FIELD AS A PART OF REALITY.
Through scientiÞc investigations, we have discovered that Þelds are as real as the material world. In fact, Þelds represent more of a fundamental reality, because the material world is nothing but a manifestation of the underlying Þelds (through energy). The Þelds cannot be seen or touched although they are unquestionably present. Their presence is revealed only when they act on material objects (or energy) with which they couple. For example, we cannot see or touch the Þeld of gravity, yet we know it is substantially real; to prove its existence, all we have to do is jump! People in general, still appear to ignore this seminal realization, perhaps because the esoteric mathematical language, in which Þelds are usually described, is unfamiliar to most. The ultimate reality is often so abstract for our visualization that an accurate description is possible only through mathematical equations. Although an equation is an elegant and quantitative representation of reality, behind every equation there is a practicable, conceptual reality, the gist of which may be appropriately conveyed sometimes by metaphors. But even for physicists, the development of the concept of a Þeld being a part of reality took almost the entire period covering the development of modern physics itself from Newton to Einstein. Unfolding the ultimate nature of the Þelds in terms of quantum Þeld theories occurred only recently.
Newton could have been the Þrst to glimpse the concept of a Þeld. But he missed it, because of the prevailing notion at the time that everything was mechanistic and material in nature. Newton realized that the earth is held in orbit around the sun by the force of gravity acting over an enormous distance without any material connection between them. He proposed a vague concept of "instantaneous action at a distance" (presumably through some material medium) to explain the gravitational attraction, although it was puzzling to him as well as to other scientists of the time.
The notion of a Þeld was Þrst introduced by Faraday, who was unencumbered by contemporary thinking. Einstein mused whether Faraday would have come up with the idea of a Þeld if he had not been a high school dropout. Faraday saw that when a magnet was moved around inside a coil, an electric current was induced in the coil, even though there was no material connection between the magnet and the coil. He explained that the magnetic Þeld, a non-material entity, was inducing a current in the coil and the concept of the Þeld was underway.
This concept was fully developed as a part of reality by Maxwell and experimentally demonstrated by Hertz. But the idea of a material world alone was still ingrained in people's minds. Therefore they came up with the proposal of a shadowy, all-pervading, material medium called ether, through which the Þeld is supposed to be transmitted. Einstein Þnally freed our thinking from the encumbrances of ether, when he came up with the idea that a Þeld is a physical state of empty space itself. According to Einstein, a Þeld is a "Þnal irreducible constituent of physical reality," and, therefore, should be considered a "fundamental constituent of the physical cosmos." Thus the concept of a Þeld as an essential part of reality came about.
Although natural phenomena appear to be very complex, the underlying force Þelds controlling their interactions are rather simple. In nature, we come across only four such Þelds, which we designate as gravity, electromagnetism, and weak and strong nuclear Þelds. In addition,there are several varieties of matter Þelds. The fundamental particles are excitations of the different underlying Þelds and are described in the standard model of particle physics. Along with the particles of the four force Þelds, they consist of three families of quarks and leptons as well as their antiparticles. These particles are listed in the tables I and II. Also each quark comes in three colors. The standard model farther anticipates a class of as yet unobserved particles,the Higg's particles which are associated with symmetry breaking and generation of particle masses.  These Þelds organize and control every aspect of the material world. But these diverse Þelds are now being proven to be just different aspects of only one Þeld, the uniÞed Þeld.

DISCOVERY OF THE UNIFIED FIELD
It was the genius of Einstein again that gave seriousness to the idea of a uniÞed Þeld. Einstein strongly believed that the known force Þelds, which control natural phenomena, have a simple uniÞed foundation. Indeed, his belief was so strong that he spent the last thirty years of his life trying to prove this concept. Unfortunately, his dream remained unfulÞlled. However, his earlier pioneering work led to the development of quantum Þeld theories that would eventually transform his vision into a reality.
UniÞcation of two very diverse forces of nature, viz., the electromagnetic and weak nuclear, have been demonstrated convincingly enough to be the subject of two Nobel prizes. The electromagnetic force has an inÞnite range, while the weak nuclear force practically vanishes at a distance as small as the size of even the nucleus itself. Yet, electroweak uniÞcation showed that these two diverse forces are actually different facets of the same force. This amazing success has broken the barrier in people's minds against the seeming impossibility of uniÞcation of nature.
In electroweak uniÞcation, the weak Þelds W ± , Z 0 and the electromagnetic Þeld are members of the same mathematical symmetry group SU (2)xU (1). Since this symmetry is the product of two separate factors, the uniÞcation of the weak and electromagnetic forces are not quite complete. A higher degree of uniÞcation of the forces and particles occur in Grand UniÞed Theories or GUTs for short. The interactions of the strong Þeld belong to the symmetry group SU(3), describing the dynamics of 'color' charges which is known as quantum chromodynamics. This is akin to U(1), which describes the dynamics of electric charges and is known as quantum electrodynamics. GUTs unify the strong, weak and electromagnetic forces as well as the quarks and the leptons.
The simplest model of this class of theories is based on a mathematical symmetry group SU (5). Since the grand uniÞed Þeld also changes quarks into leptons, most GUTs predict the proton to be unstable. The nominal SU(5) theory predict a proton lifetime lower than 10 31 years, while experimental observation indicate a lifetime larger than 10 32 years. However, the supersymmetric GUTs predict a proton lifetime consistent with the observational limit. In addition, only the supersymmetric GUTs bring about a convergence of the measured coupling constants of the strong, weak and electromagnetic Þelds. For these reasons, the nominal SU(5) theory has been abandoned in favor of supersymmetric GUTs.
Although a direct proof of grand uniÞcation has not been demonstrated, the observed abundance of matter over antimatter in the universe is believed to require such a uniÞcation. Recent observation of neutrino oscillations between its various families is considered to be a very encouraging indication of grand uniÞcation. Proton decay experiments with higher sensitivity are also in progress to provide a more direct evidence of GUTs.
A theory of Þnal uniÞcation of all the fundamental particles and forces including gravity has been a very daunting task. However, sufficient progress has now been made, especially with the development of superstring theories, so that the concept of a Þnal uniÞcation of all the Þelds of nature is being accepted as a real possibility, although a mathematically consistent formulation of uniÞcation is still being worked out. Figure 1 shows how the strength of the various forces changes with energy (per particle) or temperature. As the energy increases, the strength of the electromagnetic force increases while that of the weak nuclear force decreases moderately. (This is not apparent from the Þgure, since at ordinary temperatures, the weak force is highly reduced due to the heavy mass of its carrier particles.) From experimental data, their underlying identity has been established at an energy of about 200 billion electron volt (GeV) or a temperature of 10 15 K, where these two force Þelds behave as just different aspects of a united electroweak Þeld. The strong nuclear force decreases in strength with increasing energies and is predicted to converge with that of the electroweak Þeld at 10 16 GeV (10 29 K). The strength of the force of gravity increases continually until it is presumed to become the same with that of all the other Þelds at or near 10 19 GeV (10 32 K) where the Þnal uniÞcation of all the Þelds is thought to occur.
The Nobel Laureate Steven Weinberg, says 1 in his recent book, Dreams of a F inal T heory , "If history is any guide at all, it seems to me to suggest that there is a Þnal theory." Stephen Hawking, who is considered by many today to have the stature of Einstein, expresses it even more emphatically in his book, A Brief History of T ime. He provides some strong arguments to support his view 2 : "I think that there is a good chance that the study of the early universe and the requirements of mathematical consistency will lead us to a complete uniÞed theory within the lifetime of some of us who are around today, always presuming we don't blow ourselves up Þrst." Another Nobel Laureate, Murray Gell-Mann, gives further support to this view in his recent book, T he Quark and the Jaguar. He states 3 that "Superstring theory, in particular the heterotic form, may really be the long-sought uniÞed quantum Þeld theory." He also suggests 4 , "[that] There are many possible ways of confronting the theory with experimental results." Partly, what supports such conÞdence of the physicists about the existence of the uniÞed Þeld, is perhaps the realization that natural forces, which are so immensely diverse in our daily environment, appear to have the same strength at the natural scale of the universe. Our civilization depends on an agreed upon unit of mass, length and time like pound, foot and second. But these units are man-made. Interestingly enough, nature has its own units of mass, length and time. They would be the same for all possible civilizations anywhere in the universe and are determined by three fundamental, natural constants.
In the very Þrst paper in which Max Planck proposed his quantum theory, he was more elated about Þnding nature's units of mass, length and time than the radical consequences of quantum theory, which was not quite envisioned at that time. With his discovery of the quantum of action h, which is known as Planck's constant, he was able to determine nature's units of mass, length and time, using two other natural constants, the velocity of light c and Newtonian gravitational constant G. (Instead of the Planck's constant h, a constant h=h/2π is generally used today. However, we will use the original constant h.) The constants of nature h, c and G have the dimensional relationship in terms of mass M , length L and time T as h = ML 2 T −1 , c = LT −1 and G = M −1 L 3 T −2 . Nature's units of mass, length and time are, therefore, given by The values of the natural constant h, c and G in our units of measurements are 6.63x10 −27 erg.sec, 2.99x10 10 cm/sec and 6.67x10 −8 cm 3 gr −1 sec −2 , respectively. Using these values, we get nature's units of mass, length and time in terms of our units as 5.4x10 −5 gm (3x10 19 GeV), 4x10 −33 cm and 4.3x10 −43 sec. These units of nature, called the Planck's units in honor of its proponent, give a scale for measurements that holds true throughout the universe, and therefore, maybe appropriately called the universal scale.
The value of the Planck's units of length and time are unbelievably small compared to those of atomic or even nuclear scale. On the other hand, Planck's mass is 10 19 times larger than the mass of the proton. Although, the sizes of these nature's units appear to be so diverse, they are believed 5 to be necessary for the desirable features of the universe. The practical consequences of the diverseness of the values of the nature's units make the strength of the various forces at ordinary temperatures very disparate as shown in T able I.
But when we extrapolate our laboratory measurements, using the quantum dynamics of the highly successful models of particle physics, we Þnd that the strengths of the four forces of nature indeed tend to converge at the Planck scale. At the Planck scale, the force Þelds of nature, all having equal strength of interaction, appear to behave as just different aspects of one Þeld, the uniÞed Þeld, which additionally unites force Þelds with matter Þelds. The matter Þelds package energy into fundamental particles like quarks and electrons, while the force Þelds utilize them as building blocks to generate everything physical. The uniÞed Þeld is presumed to unify fermions and bosons through nature's supersymmetry. Thus, a uniÞed theory appears plausible to describe the underlying unity of the elementary particles that make up the physical world.

THE ORIGIN OF THE UNIVERSE
Since we have good reasons to believe in constructing a credible theory for unifying all the fundamental particles, it would be natural to inquire how the universe itself containing all these particles began. Until the twentieth century, cosmology, dealing with the subject of the creation of the universe, was mostly a part of metaphysics. Only recently, for the Þrst time in the human history, we are able to get some answers based on scientiÞc evidence about how all this came to be. This has been possible by gathering the evidence left over from the early moments of creation. By running the frames of the cosmic movie backwards, we have been able to recount the drama of creation, with the help of the theories of fundamental particle physics at very high energies. Again, the evidence points to the uniÞed Þeld as the source of the universe.
Edwin Hubble gathered the Þrst evidence of this story in the early 1920s at the Mt. Wilson Observatory. By accurately measuring the distances of the nebulae, he showed that they were not only separate galaxies, but also that they all had a redshift, implying that they were all moving away from us. Hubble also observed that the further away the galaxy was, the larger was its redshift. In fact, the speed of the recession of the galaxies, derived from the redshift, was proportional to their distance. It was soon realized that such an expanding universe was predicted by mathematical models of the universe based on Einstein's general theory of relativity. To construct a model universe, using his newly developed general theory of relativity, one essential feature used by Einstein was the cosmological principle, which states that the universe is homogeneous and isotropic. If the universe is isotropic, it can be shown to be also homogeneous. Homogeneity means that the density is distributed uniformly throughout the universe. Although it was a bold and unsubstantiated assumption at the time, since one could then locally see the dense milky way, it turns out to be an accurate one. Because on a larger scale, universe is now found to be indeed homogeneous.
The generalized solution for Einstein Þeld equations for a homogeneous universe was Þrst presented by Alexander Friedmann and therefore bears his name. The Friedmann equation for the evolution of the cosmic scale factor R(t), which represents the size of the universe, is where ρ(t) is the uniform density of the universe and k is a time-independent constant. The expansion rate of the universe is determined by ú R(t) R(t) = H(t), the Hubble parameter. At time t, it is a constant known as the Hubble constant H. Equation (4.1) shows that the speed of recession is proportional to distance, as observed at a particular time. Using R(t) and deÞning Ω(t) as the ratio of the density ρ(t) to the critical density ρ c (t) = 3H 2 (t) 8ΠG ,equation (4.1) can be expressed as It is evident from equation (4.2) that for k = +1, Ω > 1,when the universe is called closed; for k = 0, Ω = 1,the universe is ßat and for k = −1, Ω < 1,the universe is open. A closed universe will eventually collapse on itself while an open universe will expand forever.
Equation (4.1) can be recast as Differentiating equation (4.3) with respect to time, and since the total matter in a given expanding volume is unchanged, SinceR(t) is always negative, at a Þnite time in the past, R must have been equal to zero. Then, according to these models, the contents of all the galaxies must have once been squeezed together in a small volume where the temperature would have been immensely high. The radiation left over from this Þreball must still be around today, although cooled to a much lower temperature due to expansion of the universe. Precisely such a relic radiation was observed in 1965, which provided compelling evidence for the "big bang" model of the universe. This radiation is known as the cosmic microwave background radiation, at a temperature of 2.73K.
The observed radiation decoupled from the ionized soup of matter and radiation of the cooling Þreball, when electrons combined with the nuclei. The equilibrium between ionization and recombination is given by the Saha equation where x is the ionized fraction, I, the ionization potential, m e , the mass of electron and η, the number densities of baryons. Since about 90% of the nuclei are hydrogen, we can take the ionization potential to be that of hydrogen which is 13.6 eV . Since η ∼ 10 3 , the fractional ionization drops sharply at a temperature of about 4000K or at 3000K if ionization from the Þrst excited level is included. This temperature of radiation decoupling occurred at about 300,000 years after the big bang. Matter was then free to form galaxies and stars under gravitational clumping.
The primordial Þreball was a giant thermonuclear reactor. Therefore, our knowledge of nuclear reactions allows us to calculate the abundance of light elements, like hydrogen, helium, deuterium and lithium, produced in the Þreball. The observed relative abundances agree very well with theoretical predictions, which gives added support to the hot, early universe. The pioneering book by Steven Weinberg entitled, T he F irst T hree Minutes, gives 6 a comprehensive account of this model. Further support came from the observation of the minute ßuctuations in the cosmic microwave background radiation, as well as from the observed evolution of galaxies with time.
All of this evidence has established cosmology as a branch of science and the existence of the primordial Þreball appears in physics text books as part of the standard big bang model. However, there are some glaring shortcomings of the model, known as the horizon problem, the ßatness problem, etc. The proposed, inßationary paradigm, rooted in plausible theories of particle physics, offers a unique solution to these problems. It also identiÞes the source of the enormous amount of mass and energy of the big bang Þreball.
To go beyond the standard big bang model, we depend primarily upon the results of investigation of particle physics; because, towards its origin, the universe would have been smaller and the temperature increasingly higher. Such temperatures are available only in the laboratories of particle physicists today. In turn, the particle physicists look to the relics of the events of the early universe to provide support for their theories. At temperatures higher than what is attainable by machines, the only resource available for particle physicists is the study of the early universe itself. This symbiotic relationship of particle physics, (which deals with the smallest), and cosmology, (which is the study of the largest), has provided an essential link in our pursuit of an understanding of the origin of the universe.
As we proceed beyond the standard model of big bang to higher temperatures, the various stages of uniÞcation of the Þelds contemplated by the particle physicists provide a basis for recounting the early universe. Since the early universe was radiation dominated,the temperature and size is related 6 to time t by 1 T ∝ R ∝ t 1/2 except when there is a phase change. The well established electroweak uniÞcation must have been present when the temperature of the Þreball was about 10 15 K at about 10 −12 sec after the origin. Discovery of the asymptotic freedom of quarks at higher energies allows us to treat the Þreball as a super dense, weakly interacting gas containing quarks, electrons and other particles of the standard model of particle physics. At still higher temperatures, the phenomenon of inßation is presumed to have come into the picture.
Alan Guth, who conceived the idea of the inßationary theory of cosmology, gives 7 a detailed account of it in his book, T he Inf lationary Universe. A main feature of the uniÞed Þeld theories of particle physics is that a class of scalar Þelds, called Higgs Þelds, are thought to be responsible for spontaneous symmetry breaking of the various stages of uniÞcation of the Þelds.
During symmetry breaking, which separates the strong nuclear Þeld, the potential energy of the scalar Þeld is given 8 by where E GU T is 10 16 GeV , the energy scale for GUT symmetry breaking. This enormous potential energy density of the scalar Þeld can lead to an exponential expansion of the universe for a ßeeting moment (during 10 −37 to ∼10 −35 seconds after the origin), allowing the universe to expand by at least a factor of 10 30 , while maintaining a constant energy density. Consequently, a prodigious amount of positive energy can be created, balanced by an equal amount of negative gravitational potential energy, the total energy of the universe still being zero. Therefore, the big bang Þreball can essentially grow out of an embryonic universe as a result of a momentary instability of a scalar Þeld, and the basic features of the baby universe become established. Guth amusingly describes this by his famous phrase, "In the context of inßationary cosmology, it is fair to say that the universe is the ultimate free lunch." Even though cosmologists generally agree on the necessity of an inßationary paradigm, no such agreement exists on its details or exactly when it occurred. Some superstring cosmology model suggests its occurrence to be even much closer to the Planck's dimensions. At its present stage of development, the inßationary universe is more of a model whose actual details still need to be Þnalized, based on some observations, such as the characteristics of ßuctuations of the cosmic microwave background radiation. Especially, the study of the pattern of polarization of these radiations caused by the primordial gravitational waves could distinguish between the different scenarios of inßation. Some inßationary model even envisions multiple universes or a multiverse arising out of continuing inßation. In such a model, the beginning of the universe is pushed back to an indeterminate past.
In our universe today, the cosmic microwave background radiation essentially looks the same in all directions, coming from regions, which can not be connected even with the speed of light. This is known as the horizon problem. But if the universe initially started with a small enough size before inßation, there would have been time for communication between the various regions. This would explain why the universe, as represented by the microwave background radiation, is so isotropic and homogeneous, on a large scale. The observed smoothness of the microwave background radiation also provides a graphic validation of the cosmological principle.
Equation (4.2) shows that the value of the critical density Ω(t) determines whether the Universe is open, closed or ßat. Any deviation in the value of Ω from 1 in the early universe would rapidly grow with time. If Ω was slightly less than 1 in the early universe, it would have rapidly fallen to zero resulting in a universe with no structures such as galaxies and stars. Instead, if Ω was slightly greater than 1, it would have rapidly increased and the universe would have already collapsed. The age of the universe has been determined to be 10-20 billion years by a variety of independent methods such as expansion rate of the universe, radioactive dating, oldest stars in globular clusters, Sunyaev-Zeldovich effect, gravitational lensing, cooling of white dwarf star etc. For the universe to be this old with the observed structures, it had to start out with Ω = 1, with an accuracy of about 1 part in 10 60 which is rather unnatural. This is referred to as the ßatness or the age problem.
During the process of inßation, the term kc 2 /H 2 R 2 in equation (4.2) is suppressed enormously 8 , so that the universe starts out with Ω = 1. This is also supported by recent observations 9 showing that the universe today is actually ßat. However, the observed 10 mass density of the present universe appear to give Ω m of only 0.3-0.6. To reconcile the value of Ω = 1 with the observed low mass density, the existence of a vacuum energy density, consistent with a cosmological constant Λ, has been proposed. Recent measurements 11 of H at high redshifts, using type I a supernovae, indicate that the value of H in the present epoch is actually increasing, rather than decreasing, as has been assumed before. The observation has prompted the existence of a small value of Λ to be taken seriously. While constructing a model universe, Einstein originally introduced Λ to Þnd a static solution of his Þeld equations. He abandoned it as his "biggest blunder" when the static solutions turned out to be unstable and the universe was actually found to be expanding. A non-zero value of Λ is being introduced now to explain the observed ßatness of a low density universe. Accordingly, equation (4.1) is modiÞed as (4.8) By deÞning ρ Λ = Λc 2 8ΠG and an effective ρ e (t) = ρ(t) + ρ Λ ,equation (4.8) can be written in the identical form as equation (4.1), Thus the existence of Λ can be represented as a Þxed mass density of the vacuum. Since the value of Λ is small (∼ 10 −56 cm −2 ), its effect is signiÞcant only at large values of R, and therefore its exclusion is justiÞed for the early and adolescent universe, except for the extraordinary circumstances during the ßeeting inßationary period. When the cosmological constant is included, equation (4.2) becomes . (4.10) Again, during inßation kc 2 /H 2 (t)R 2 (t) is suppressed enormously 8 , so that the relation holds to a high degree of accuracy. We can then consider Ω = Ω m + Ω Λ = 1,where Ω m = ρ m /ρ c and Ω Λ = ρ Λ /ρ c = Λc 2 /3H 2 . By integrating equation (4.8) using Ω Λ, the present age t 0 of the universe is given by Taking the recent accurate value of H 0 = 65 ± 10 km sec −1 Mpc −1 and Ω Λ = 0.6, the value of t 0 is about 13.4 billion years. This age is consistent with the recent determination 12 of the age of the oldest stars in the globular clusters to be 12-14 billion years. If the critical density of the universe today consisted only of matter, the age of the universe would be t 0 = 2/3H −1 0 ≈ 10 billion years, which is lower than the age of the oldest stars. This provides a compelling reason for resurrecting Λ. Furthermore, the observed ßatness of the universe and estimates of Ω m and H 0 , combined with the preliminary value of Λ obtained from the high redshift supernovae studies, satisÞes equation (4.11) to a large extent, which gives signiÞcant support to the inßationary paradigm.
The quantum ßuctuations of the scalar Þeld also become enlarged by the process of inßation, which provides the seed for subsequent galaxy formation. These minute density ßuctuations imprint tiny temperature variations (about six parts per million) over the smooth, microwave background radiation, recently discovered 13 by the COBE satellite. The pattern of ßuctuations observed by COBE as well as by some recent experiments is consistent with those predicted by the inßationary model and inconsistent with other postulates like topological defects. Further studies are planned with more sensitive MAP and PLANCK satellites which are expected to provide some indication of the type of inßation,in addition to furnishing accurate values of cosmological parameters such as H, Ω m, Ω Λ etc.
According to the prevailing notions, what preceded the inßationary universe is known as the GUT epoch. Our knowledge at the beginning of the GUT epoch is quite murky, primarily due to our inability to correlate it to any observable data. Still, some attempts have been made to clarify the picture as we Þnally approach the origin. Before inßation increased it, the size of the universe would have been about 10 −30 cm. At earlier times, the universe must have been constrained to even smaller, gradually diminishing sizes. According to general theory of relativity, as we approach the origin, spacetime will end up at a point known as singularity, where all the classical laws of physics will break down. But before reaching the conjectured singularity, quantum effects should come to the rescue at Planck's length of 10 −33 cm. The subject of quantum cosmology has been developed to deal with this problem. The quantum cosmological aspect of the superstring theory makes a prediction 14 that space can not contract beyond its minimum at the Planck length.
Hartle and Hawking have developed 15 a unique version of quantum cos-mology using sum over histories and imaginary time. According to their solution, a singularity is avoided by describing the initial conditions of the universe with quantum effects, whereby space and time together form a surface that is Þnite in size but does not have a boundary. This is how the surface of the earth would appear to a hypothetical, two dimensional ßatlander living on the surface of a sphere. The earth would be Þnite in size, but there would be no boundary, or edge to fall off. Hawking calls this proposal a "no boundary" boundary condition. Murray Gell-Mann lends some support 16 to this effort in his book, T he Quark and the Jaguar: "If the elementary particles are indeed described by a uniÞed theory (which Hartle and Hawking did not explicitly assume), then the appropriately modiÞed version of their initial condition can be calculated in principle from that uniÞed theory, and the two fundamental laws of physics, for the elementary particles and the universe, become a single law." Thus the uniÞed Þeld and the initial condition of the universe are assumed to be mutually consistent.
Although there is no general consensus on how the universe initially came to be, the most plausible explanation yet is that an energetic ßuctuation caused the universe to begin from the Planck's dimensions. The spontaneous symmetry breaking of the uniÞed Þeld occurred, thereby separating gravity, matter Þelds and GUT force Þeld, as well as initiating the expansion of the universe. The universe cooled by expansion to cause another symmetry breaking, when the strong Þeld separated along with the creation of the primordial Þreball by inßation. As the temperature cooled by further expansion, the weak and electromagnetic Þelds separated; all the force Þelds and the matter particles assumed their separate identities. Thus, the uniÞed Þeld sequentially unfolded to create this universe and everything physical in it.

THE EVER-PRESENT UNIFIED FIELD
The quantum physical presence of the uniÞed Þeld everywhere in the fabric of spacetime today can be understood in terms of the inescapable consequences of the quantum Þeld theory and Heisenberg's uncertainty principle, which represent the essence of the quantum nature of the ultimate reality. According to the quantum Þeld theories,the fundamental elements of reality are the underlying quantum Þelds. Every elementary particle is an excitation of its respective underlying Þeld. Furthermore,all Þelds are present in all space throughout the universe at all times. However,to be consistent with the uncertainty principle,no quantum Þeld can be at rest. All the Þelds that are manifest since the early moments of the universe should be present as vacuum ßuctuations even when they are not coupled or localized. The ubiquitous existence of vacuum ßuctuations of the electromagnetic quantum Þeld is readily observed in the Casimir effect, the Lamb shift and a variety of other phenomena.
The Casimir effect predicts that vacuum ßuctuation of the electromagnetic Þeld will induce a force between two uncharged conductors, separated by a small distance in vacuum. Such a force has been measured 17 recently by Lamoreaux. The Lamb shift was observed 18 by Willis Lamb, for which he was awarded the Nobel prize. Lamb observed an unexpected spectral line splitting in hydrogen,which stimulated the development of quantum electrodynamics and established the effect of vacuum ßuctuation. The tiny magnetic moment of the electron is also affected by vacuum ßuctuations; the measured value agrees with prediction deduced from vacuum ßuctuations to better than eight decimal places.
Thus, empty space is not empty at all. On the contrary, the quantum vacuum is the "home" of nature's inÞnite dynamism. It is the substrate in which all of high energy physics takes place. But this frenzied activities of the empty space must be subject to some systematic order.The vacuum state of a quantum Þeld should correspond to a superposition of the ßuctuation of all possible Þeld shapes. Since the vacuum state represents the absence of all real physical particle and forces, it should possess spatial symmetry in conformity with P oincaré invariance, which would preclude arbitrary superposition of Þelds.
Our knowledge of the uniÞcation of the Þelds can guide us to determine how the Þelds in the vacuum state may be farther organized. The electroweak uniÞcation happens when the symmetry represented by SU(2)xU(1) is restored. This has been demonstrated experimentally, using particle accelerators, where the energy E per particle was about 200 GeV,corresponding to an equivalent temperature of 10 15 K. The wavelength λ of a particle of 200 GeV is given by λ = hc/E v 10 −16 cm. Thus, when we probe the spatial distance at about 10 −16 cm, the presence of the symmetry required for the electroweak uniÞcation becomes evident.
To probe what happens at shorter and shorter distances, we need higher and higher energy per paritcle, since the distace probed depends upon the wavelength of the particle which depends inveresely upon its energy. With the present or anticipated experimental capabilities,we can not probe dis-tances much shorter than 10 −16 cm. Fortunately, however, calculations using supersymmetry, show that if the forces are examined as they act on distances of about 10 −30 cm, the strength of the electromagnetic, weak and the strong nuclear forces appear to become equal. This would indicate that the GUT symmetry is restored at about 10 −30 cm, even in the absence of very high temperatures.
Detailed quantum Þeld theoretic analysis on a tiny time slice indeed show that, with the exception of any phase transition characteristic of a cooling,high temperature ensemble, physics at fundamentally small dimensions is equivalent to physics at high temperatures. Therefore, restoration of the GUT symmetry at about 10 −30 cm at ordinary temperatures is based on some solid theoretical foundation.
Finally, at Planck's dimension,the calculations show that the strength of the gravitational force become equal to that of the three guage forces. Thus,as we proceed towards Planck's length anywhere in the universe, all the symmetries of nature are restored gradually, thereby creating the conditions for the various stages of uniÞcation of all the forces possible in sequence. Furthermore, supersymmetry is surmised to unify the bosons and the fermions. Thus, at the Planck scale,where all of nature's symmetries are presumed to be restored, all the underlying quantum Þelds should behave as just different aspects of a single uniÞed Þeld. Even though,the high temperatures necessary for uniÞcation are physically absent today in the Planck's dimension of the vacuum, presence of the uniÞed Þeld is possible from a quantum physical perspective.
A mathematically consistent Þnal theory of the uniÞed Þeld is still being worked out. In the absence of such a theory, the basic principle of the much tested general theory of relativity may be applied to get an over all framework of quantum gravity and quantum cosmology which can serve to conceptualize the nature of the ultimate ground state of the vacuum, although its mathematical formulation is inadequate for a quantum description of nature. The fundamental tenet of Einstein's general theory of relativity is that space, time and matter (or energy) cannot exist separately. As an outcome of the special theory of relativity, space and time are inseparable. According to the general theory of relativity, space and time are not just passive background in which events take place, but rather they are active participants in the dynamics of the universe. In Einstein's words 19 , "the physical reality of space is represented by a Þeld whose components are functions of spacetime " . Therefore, a Þeld is not only an irreducible physical state of space itself, spacetime and Þelds must also exist simultaneously.
In addition, we know that in the quantum domain, systems can possess a minimum quantum energy without having to dissipate it. The ground state energy of an atom and zero point energy of vibration of a molecule are typical examples. In the superstring formulation, the uniÞed Þeld can vibrate forever without loosing its energy, while the coordinates of spacetime possess quantum mechanical characteristics. As Steven Weinberg says 20 in his book, Dreams of a F inal T heory, "In contrast, the strings that concern us here are truly fundamental and keep vibrating forever; they are not composed of atom or anything else, and there is no place for their energy of vibration to go." Therefore at Planck scale, the ßuctuating spacetime geometry, and the "zero point" ßuctuation of the uniÞed Þeld can be deemed to constitute the self-interacting dynamics of the vacuum ground state of the universe.
Since spacetime is not expected to contract beyond Planck scale, uniÞed Þeld may be considered to be present in the ultimate fabric of spacetime everywhere in the universe. During the earliest moments of creation of the universe, when the temperature dropped as the universe expanded, the various Þelds sequentially became manifest. Equivalently, from a quantum physical perspective, this process of sequential differentiation of the uniÞed Þeld into its various components takes place, as the dimension of space encountered becomes larger than the Planck length today. This is schematically shown in Fig. 2. The various Þelds manifest themselves whenever appropriate energy or matter is available for them to couple. Thus, the structure and dynamics of the vacuum state foreordain all the properties of the fundamental particles that arise out of it. This is why any fundamental particle has its exact same particular properties everywhere in the universe. The properties of the fundamental particles, in turn, govern the characteristics of all physical interactions, which then owe their ultimate origin to the uniÞed Þeld.
In summation, recent scientiÞc discoveries point to the fact that uniÞed Þeld sequentially unfolded to create our universe. The uniÞed Þeld, is still present in the very fabric of spacetime throughout the universe in a quantum physical way, thereby upholding and administering at least everything physical it contains. It seems nature has repeated this pattern in the characteristics of the human genome. Following the analogy of the genome, should we not then call the uniÞed Þeld the universal Þeld, possessing the universal blueprint?
Based on a lecture delivered at the International Symposium on Mathematical Physics in memory of S. Chandrasekhar and Abdus Salam on De-