PoS(CMB2006)003 , on nce http://pos.sissa.it/ ce. undamental . In this ple- e at the next and future generations of ections between cosmology and parti- ive Commons Attribution-NonCommercial-ShareAlike Licen CMB and Physics of the Early International Confere † ∗ [email protected] colliders. cle physics, focusing on physics at the TeV scale, accessibl nary talk, delivered at the the island of Ischia, Italy, in 2006, I discuss the broad conn Modern cosmology poses deep and unavoidable questions for f Speaker. A footnote may follow. ∗ † Copyright owned by the author(s) under the terms of the Creat c CMB and Physics of the Early20-22 Universe April 2006 Ischia, Italy

Syracuse University, USA E-mail: Mark Trodden Physics of the very early Universe:learn from what particle can collider we experiments? PoS(CMB2006)003 7, . 0 1) we ∼ Λ = Ω total Mark Trodden Ω 0, = . 4 k ) 3, we obtain . 0 eV 3 ∼ as well understood; after all, − rst is from Type Ia supernovae smic Microwave Background a new understanding of these e, and pointing out the places M ill be very sparse, restricted to a 10 ology, there is one fundamental f the universe have provided a ( Ω nections between collider experi- d the notice of particle physicists. ns no appreciable primordial anti- e very important piece of data that ws a substantial range of possible ∼ e, sufficiently negative to cause the rk energy. by this decision. minated by a cosmological constant ear collider may rule out or provide of our approaches to these issues. In 3 niverse. There now exists compelling t are firmly rooted in . r can find more complete references. I s not the case, then precision measure- synthesis rests on the requirement that, 5, 6, 7, 8] for some alternative views). cm ticle collider experiments? n about interpreting the acceleration data / mposed of 5% baryonic matter, 25% dark erg . For a flat universe ( 8 − total 10 2 Ω ∼ Λ 220. Such a peak is seen in the WMAP data, yielding ρ ' l . However, if we independently constrain Λ Ω 08 (95% c.l.) – strong evidence for a flat universe. . 1 and ≤ M Ω total Ω ≤ Direct observation shows that the universe around us contai One would think that the baryonic component of the universe w The second is from studies of the small anisotropies in the Co Beyond these topics, I will briefly speculate on possible con Since this is a summary of a conference talk, my referencing w I will begin by inventorying the energy budget of the univers The data-driven revolution in cosmology cannot have escape The best known evidence for this comes from two sources. The fi 98 . matter. In addition, the stunning success of big bang nucleo we are made of baryons. However,issue from to the be point understood. of view of cosm 3. The Baryon Asymmetry of the Universe expect a peak in the power spectrum at 0 corresponding to a vacuum energy density Radiation (CMB), culminating in the WMAPthe satellite CMB [11]. fluctuations On give us is the value of where our understanding is seriously hamperedI by will issues then tha go on tosome describe cases, in most broad notably terms dark theevidence matter current for status and existing baryogenesis, proposals. a On lin ments the other of hand, physics if at this thefundamental i cosmological TeV conundrums. scale may very well point the way to ments and one of the most esoteric cosmological concepts - da few experimental results, some references to act as a cautio During the last decadeclear a and surprising host accounting of of theevidence, new energy from precision budget multiple techniques, of measurements that the the u o universe is co too literally, and some review articles from which the reade matter and a whopping 70% dark energy, with negative pressur Physics of the very early Universe: what can we learn from par 1. Introduction apologize in advance to any colleagues who may feel slighted 2. The New Cosmological Paradigm expansion of the universe to accelerate (although see [3, 4, studies [9, 10]. These data arethan much by better a fit by flat avalues matter-dominated universe of do model. This result alone allo PoS(CMB2006)003 (3.1) from precise Mark Trodden ven by Grand 10 10 − − 10 10 × × (the composition of 2 3 . . 0 0 − + CP of the electroweak phase s, and is observed exper- . This appears to be much 10 hermal activation. c − T 20 . − 10 = 10 − r generating the baryon number he gauge fields. In terms of the × onentially suppressed. However, urn to extensions of the minimal T attractive, it is not likely that the baryon asymmetry of the universe ter, to today, what processes, both 1 10 . n is central to electroweak baryoge- focus on this here. In the standard y. However, baryon number is vio- to be the entropy density, equilibrium is insufficient to lead to 6 he universe cooled from early times, × than 10 s ve background (CMB) acoustic peaks on was first addressed by Sakharov in ture ion quantum tunneling occurs around esult in the electroweak theory being without the aid of phase transitions. is more complex. 2 = es. These effects are closely related to . model (MSSM). e generation of this very specific baryon ticle collider experiments? 6 le future. η mena is extremely accurate at electroweak mixing. However, the relevant effects are < ¯ 0 b ¯ n K s , − 0 3 b K (charge conjugation) and n C ≡ η ) symmetry. < B 10 − 10 × 6 . 2 ways to achieve these. One particularly simple example is gi ) C many to be the number density of (anti)-baryons and ) -violating vacuum transitions may occur frequently due to t ¯ b ( B b n Violation of the discrete symmetries Violation of the baryon number ( parity and A departure from thermal equilibrium. The question of the order of the electroweak phase transitio For a continuous transition, the associated departure from in the electroweak theory are chirally coupled to t CP is known not to be an exact symmetry of the weak interaction There are In recent years, perhaps the most widely studied scenario fo At zero temperature, baryon number violating events are exp If we’re going to use a particle physics model to generate the • • • too small to account fortheory. the In observed particular BAU the and minimal so supersymmetric it standard is usual to t nesis. Since the equilibrium description of particletemperatures, pheno baryogenesis cannot occur at such low scales relevant baryon number production. For a first order transit parametrized by a dimensionless constant which is no larger discrete symmetries of themaximally theory, C-violating. these However, the chiral issue couplings of CP-violation r imentally in the neutral Kaon system through transition, at temperatures above or comparable to the critical tempera Unified theories (GUTs). However, whilephysics GUT involved will baryogenesis be is directly testable in the foreseeab of the universe has beenelectroweak electroweak theory baryogenesis baryon and number is Ilated an will at exact global the symmetr quantum levelthe through nontrivial nonperturbative vacuum process structure of the electroweak theory. measurements of the relative heights ofby the first the two WMAP microwa satellite. Thusat the which natural one question would arises; expect as equalparticle t amounts physics of and matter cosmological, and were antimat responsibleasymmetry? for (For th a review and references see [12, 13].) (BAU), what properties must the theory1967, possess? resulting This in questi the following criteria This number has been independently determined to be Physics of the very early Universe: what can we learn from par defining PoS(CMB2006)003 , the (3.2) (3.4) ) c T ( bubbles, v HC should = Mark Trodden i φ . At one loop, e written as h critical 2 ht scalar particles d Φ physics. For these, B . In addition, there are and h 1 Φ t satisfied. This is therefore train the Higgs mass to be n which these requirements iggs e begins. At a particular tem- is at least a good candidate for enesis within a particular SUSY servable in s a point in space, the Higgs fields minimum of the finite temperature ressed. Since baryogenesis is now librated to zero. Such an effect is and the departure from equilibrium atron collider. Important supporting t is in the true vacuum, baryogenesis ttice results indicate that the allowed ryogenesis to succeed. ng the transition. As they, bubble as walls do the other fields and this leads hrough breaking. Al- ictions: If the Higgs is found, the next gible at this temperature in the broken ars have masses in the correct region of f the phase transition is strongly enough ticle collider experiments? roweak baryogenesis scenario to be suc- rion in this way. CKM-like effects in the chargino mixing 0 in the unbroken phase to . = , 1 i t φ m ≥ h 4 ) 120GeV (3.3) ≤ c c T T ≤ ( v ˜ t h m m 5. In the next few years, experiments at the Tevatron and the L > i 1 of the asymmetry and the criterion for this not to happen may b Φ (the superpartners of the top quark) in the theory. These lig , bubbles just large enough to grow nucleate. These are terme h c ˜ / t T i 2 Φ 4 GeV, it is clear from numerical simulations that (3.2) is no stops . washout ≡ h and nucleation of bubbles of the true vacuum in the sea of fals β 114 c T What would it take to have confidence that electroweak baryog One important example of a theory beyond the standard model i In the minimal standard model, in which experiments now cons There is a further criterion to be satisfied. As the wall passe Now, the two Higgs fields combine to give one lightest scalar H > = H model actually occurred? First, theretest are will some general come pred from theevidence search will for come the from lightest CP-violating stop at effects which the Tev may be ob probe this range of Higgs masseselectroweak and baryogenesis. we should know if the MSSM perature below Physics of the very early Universe: what can we learn from par T a second reason to turn to extensions of the minimal model. can be met is the MSSM. In the MSSM there are two Higgs fields, It is necessary that this criterion be satisfied for any elect m cessful. first order it is possible to satisfy the third Sakharov crite and they expand, eventually filling allpass of each space point and in completi space,to the a order significant parameter departure changes from rapidl thermal equilibrium. Thus, i evolve rapidly and the Higgs VEV changes from value of the order parametereffective at potential, the in symmetry the breaking global occur broken while phase. the Higgs Now, field CP ishas changing. violation ended, Afterwards, and the baryon poin over, number it violation is is imperative that exponentially baryonphase, sup number otherwise violation any be negli baryonicknown excess as generated will be equi a CP-violating interaction between theseternatively, there fields also is exists induced extra t matrix. CP-violation Thus, through there seems to be sufficient CP violation for ba also light for tan can lead to a strongly firstparameter order space. phase A transition if detailed the tworegion scal loop is calculation given by [14] and la PoS(CMB2006)003 (4.2) (4.1) ll later t term on dard Model Mark Trodden different from ) γ s → b ( e can clearly see why it is s to a WIMP. Obviously, a le model. For this we require is the annihilation cross-section ng Massive Particles (WIMPs). his equation dominates and one ter, some of which are accessible emaining today is given by , y would certainly be too little to nching ratio depends strongly on σ ion. After this point, annihilations ) t, uilibrium one at those temperatures. ld the correct order of magnitude to s it reaches a temperature, known as ng ratio BR a detailed calculation is required to 2 eq and branching ratios to compare with , is attractive for entirely independent o collider physicists (for a review and s not space to review all of these here. cing case would require both the LHC n , te of this type arises in supersymmetric tivity and hence in principle testable at ticle collider experiments? −  χ 2 n ( σ weak i v σ . The evolution of the number density of these σ  5 χ 1 . − h 0 χ particles. If this were always the case then today we ∼ Hn χ 3 DM − Ω . χ = n χ ˙ n particles at that time is merely diluted by the expansion at a χ parameters, the typical difference with respect to the Stan , at which the evolution equation become dominated by the firs t A and µ is the typical weak interaction cross-section. From this on weak is the equilibrium value of σ eq In fact, to a first approximation, the dark matter abundance r A prime class of dark matter candidates are Weakly Interacti However, what is really necessary is to establish a believab Theorists have developed many different models for dark mat What I have just described is a generic picture of what happen In the early universe, at high temperature, the last term in t n freeze-out temperature times, leading to an abundance thatThis is is much illustrated higher in than figure the 1 eq [16]. to terrestrial experiments and some ofRather, which I are will not. focus There on i areferences specific see example [15]). that is of interest t Such a particle would be a new stable particle prediction is of the orderthe of BaBar, the Belle present and experimental BTeV experiments. sensi precision measurements of the spectrum,theoretical masses, requirements couplings for a sufficient BAU. Suchand a ultimately convin the ILC if this is truly how nature works. 4. Dark Matter the right- hand side - thecease damping and due the to distribution the of the Hubble expans and would find negligible numbersaccount of for them the and dark their matter.the However, energy as densit the universe expand that WIMPs get their nameexplain - the dark weakly matter. interacting particles yie specific candidate undergoes veryyield specific the correct interactions relic abundance. and Theextensions most popular of candida the standard model. Supersymmetry, of course particles in an expanding universe is finds the equilibrium number density of where Physics of the very early Universe: what can we learn from par the preferred parameter space leads to values of the branchi where a dot denotes a time derivative, H is the Hubble constan the Standard Model case.the Although value the of exact the value of this bra PoS(CMB2006)003 Mark Trodden and the universal 0 m re 2 [17] the LSP is ements directly relevant nalysis requires us to focus ucial and manageable set of tand all the possible ways for ne the relic density of such a . If it is a neutralino, it is almost ergravity (mSUGRA) - described sonable Higgsino component for R llider. ˜ τ m, I would like to mention at least GeV. ate for the dark energy, and collider ith the known dark matter abundance. ersal scalar mass e interest of not giving up hope, and f the standard model particles. This 16 lings in the theory, a goal that, although SUSY with low-energy SUSY breaking 10 ticle collider experiments? al, weakly interacting, with a weak scale × 2 ' 6 GUT M or the right-handed stau χ The co-moving number density of a dark matter particle. , both defined at the scale Figure 1: 2 / 1 M 1TeV. What might the LSP be in this framework? As can be seen from figu As I have mentioned, it is hard to see how one might make measur If SUSY is discovered at colliders, one would like to determi It is, of course, very important to go beyond mSUGRA to unders Weak scale SUSY has a large number of parameters. A detailed a 1 10 100 1000 ≥ 0.01 0 0.001 0.0001 typically the the lightest neutralino gaugino mass to the dark energy problembecause in we colliders. appear to Nevertheless, beone in extremely connection th ignorant between about the this cosmologicalphysics. proble constant, a candid particle to an accuracy of a fewThis percent, requires in a order precise to determination compare of w the masseschallenging, and may coup well be possible with the LHC and a linear co 5. Dark Energy an LSP to be thecommon dark models. matter. However, mSUGRA does provide a cr mass, and hence can be a compelling dark matter candidate. particle physics reasons. However, a naturaland prediction R-parity of is theLightest existence Supersymmetric of Particle (LSP) the is lightest typically neutr superpartner o on particular models. It is commonby to just 5 use parameters, a the model most - important of minimal which sup are the univ purely Bino over am large region of parameter space, with a rea Physics of the very early Universe: what can we learn from par PoS(CMB2006)003 (5.2) (5.1) 0. > Mark Trodden µ 10, and = β o the cosmological constant 0, tan our understanding of physics at is a completely free parameter. on of accelerators is the possibil- = modes of a quantum field in the y implying a certain spectrum and f magnitude to explain cosmic ac- 0 e ratio of these quantities changes Λ expectation. f component to another. A , above which ignore any potential . bably true, I would like to emphasize views see [18, 19, 20]). In addition, f the universe’s history during which sulting some of my colleagues, when 4 mponent he context of collider signatures, it is ) tunately this integral diverges, yielding ustify this. If the cutoff is at the Planck ly thought unlikely that collider physics his problem. ticle collider experiments? , 4 ) GeV eV 18 3 − 10 ( 7 10 arises because our best-fit universe contains vacuum ( ∼ 4 P ∼ M vac ∼ ρ vac ρ coincidence problem A portion of the mSUGRA parameter space with Figure 2: A second puzzle, the Unfortunately, a cosmological constant of the right order o In classical general relativity the cosmological constant To date, I think it is fair to say that there are no approaches t As I have mentioned, a prime motivation for the next generati which is 120 orders of magnitude smaller than the above naive Physics of the very early Universe: what can we learn from par celeration must satisfy However, if we integratevacuum, over we the obtain a quantum natural expectation fluctuationsan for of its infinite scale. all answer Unfor for theextremely vacuum high energy. energies, Since we wecontributions, could do expecting introduce that not a a trust more cutoff completescale, energy theory we will obtain j an estimate for the energy density in this co and matter densities of therapidly same as the order universe of expands. magnitude.we there could is Since observe only th the a transition brief from epoch domination o by one type o ity that supersymmetry might be discovered.one At is the constantly risk of dealing in witheasy supersymmetric to forget theories that in supersymmetry t is much more than a symmetr problem that are both well-developedgiven and the compelling absurdly small (for mass re scaleswill involved, it have any is impact general on this problem.a While particular I connection think between this collider is experiments pro and t PoS(CMB2006)003 (5.3) space-time Mark Trodden ctions and in particular my ce. I also owe thanks to my of freedom there is a matching hy it is that we do not observe phasized the deep connections le, there is no selectron with the t long ago). Therefore, if super- er grant PHY-0354990. MT is a Michael Peskin for many useful matter and perhaps all the way to ental questions are the same and d cosmology, as disciplines inde- , tributions to quadratic divergences erarchy problem and hence that the e vacuum energy, for fermions the 4 ight into how this occurs and perhaps milar effect occurs when calculating ) symmetry is, of course, a de. If we find SUSY at colliders and logy such experiments hold the key to tly match, the net vacuum energy sums his is still 60 orders of magnitude away ticle collider experiments? al if we are to construct a coherent story h those of the Poincaré group. There is a d from future ones and the puzzles facing . In a theory with broken supersymmetry, GeV 3 10 SUSY ( M 8 ∼ 4 SUSY M ∼ vac ρ It is a crucial aspect of the dark energy problem to discover w In this lecture I have tried to argue that particle physics an From the familiar baryonic matter, through the elusive dark I would like to thank the organizers for a wonderful conferen We do not, however, live in a supersymmetric state (for examp The power of supersymmetry is that for each fermionic degree the vacuum energy is not expected to vanish, but to be of order where I have assumed that supersymmetrysuperpartners are is close relevant to to experimental the bounds. hi from However, the t observed value. a cosmological constant anything likeunderstand this how it order is broken, of this magnitu may provideprovide much new needed information ins about the vacuum energy problem. 6. Conclusions pendent of one another,that no we longer are exist; approaching that thembetween our results in obtained most complementary in fundam ways. existing colliderscosmology and I expecte regarding have the em energy budget of the universe. the mysterious dark energy, collider experiments are cruci of cosmic history. In conjunction with observational cosmo unlock the deepest secrets of the universe. Acknowledgments co-members of the ALCPGco-editors Working Group Marco on Battaglia, Cosmological Jonathan Conne conversations. Feng, This Norman work Graf was supportedCottrell and Scholar in of part Research by Corporation. the NSF und same mass and charge assymmetry an exists, electron, it or must we be would broken have at noticed some i scale bosonic degree of freedom,cancel, and allowing vice-versa, a resolution so of thatthe the their vacuum hierarchy energy: con problem. while Acontribution bosonic is si negative. fields Hence, contribute if a degreesto of zero. positiv freedom exac Physics of the very early Universe: what can we learn from par specific relationships between couplings and masses. Super symmetry, relating internal symmetry transformations wit direct connection between this fact and the vacuum energy. PoS(CMB2006)003 , 195 267 Mark Trodden , 565 (1999) 517 J. , 043528 (2004) , 1009 (1998) , 24 (2003) 70 116 650 ys. B tric dark matter,” Phys. Rept. s. Rev. D odden and M. S. Turner, Phys. Rev. D , 208 (2000) [arXiv:hep-th/0005016]. , 044023 (2002) 65 ticle collider experiments? k matter in focus point supersymmetry,” 485 , 35 (1999) [arXiv:hep-ph/9901362]. , 373 (2000) [arXiv:astro-ph/9904398]. h/0303041. 49 9 , 559 (2003) [arXiv:astro-ph/0207347]. 9 75 , 135 (2003) [arXiv:astro-ph/0302217]. , 1 (2002) [arXiv:astro-ph/0201229]. 148 540 , 1463 (1999) [arXiv:hep-ph/9803479]. , 1 (2001) [arXiv:astro-ph/0004075]. 4 , 199 (2001) [arXiv:hep-th/0010186]. 71 , L11 (2003) [arXiv:hep-ph/0405215]. 502 [Supernova Cosmology Project Collaboration], Astrophys. C0307282 [Supernova Search Team Collaboration], Astron. J. , Astrophys. J. Suppl. , 388 (2000) [hep-ph/0004043]. et al. 482 et al. et al. , 063513 (2005) [arXiv:astro-ph/0410031]. [arXiv:hep-ph/0208043]. (1996) [hep-ph/9506380]. Phys. Lett. B [arXiv:astro-ph/0105068]. 71 [arXiv:astro-ph/0306438]. [arXiv:astro-ph/9805201]. [arXiv:astro-ph/9812133]. [2] C. Deffayet, Phys. Lett. B [3] C. Deffayet, G. R. Dvali and G. Gabadadze, Phys. 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